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APA1433
) Alaska Power Authority Susitna Hydroelectric Project Subtasks 4.01 through 4.08 INTERIM REPORT ON SEISMIC STUDIES FOR SUS~TNA HYDROELECTRIC PROJECT December 1980 Prepared by WoodwardcCIIYae Consun:ants Alaska Resources Library & fnfonnation Services Anchorage, Alaska for Acres American Incorporated 1000 Liberty Bank Building Main at Court Buffalo, New York 14202 Telephone: (716) 853-7525 PREFACE This interim report presents the results of the seismic studies con- ducted during 1980 for the Preliminary Feasibility Study of the proposed Susitna Hydroelectric Project site. These studies include geologic evaluation of faults and lineaments, an historical and microearthquake seismicity study, and preliminary estimation of ground motions. The results of this interim report are being used as the basis for seismic geology and ground motion studies which are scheduled for 1981. The report includes 14 sections which summarize the results of the studies to date. The eight appendices present support data for the interpretations and conclusions presented in Sections 1 through 14. Tables and figures appear at the end of each section and appendix. Measurements reported in this volume typically \vere made in the metric system and then converted to the English system. For these conversions, the measurements reported in the English system are rounded off to the nearest single unit (e. g., 70 km converts to 43 miles) even when in the context of the sentence the conversion should be rounded off to the nearest ten units (e. g., 70 km converted to 40 miles). This was done to retain the original number used to make the conversion. Conversely, some measurements were made using the English system; in this case, the conversion to the metric system also has been rounded off to the nearest single unit. Both sets of numbers have been presented for the conven- ience of the reader. TABLE OF CONTENTS PREFACE TABLE OF CONTENTS LIST OF TABLES LIST OF FIGURES DEFINITIONS OF KEY TERMS ACKNOWLEDGMENTS 1 -SUMMARY ------------------------------------------------- 1.1 -Project Description ----------------------------- 1.2 -Conceptual Approach ------------------------------ 1.3 -Method of Study ---------------------------------- 1.4 -Tectonic Model ----------------------------------- 1.5 -Candidate Significant Features ------------------- 1.6 -Significant Features ----------------------------- 1.7 -Seismicity --------------------------------------- 1.8 -Reservoir-Induced Seismicity --------------------- 1.9 -Preliminary Maximum Credible Earthquakes (PMCEs)-- 1.10 -Preliminary Ground Motion Studies ----------------1.11 -Conclusions _____________ .:. ____ :.. __________________ _ 1.12 -Proposed 1981 Study Plan ------------------------ 2 -INTRODUCTION -------------------------------------------- 2.1 Project Description and Location ----------------- 2.2 -Objectives --------------------------------------- 2.3 -Scope ------------------------------------------- 2.4 -Fault Study Rationale ---------------------------- 2.4.1 -Conceptual Approach ---------------------------- 2.4.2 -Surface Rupture and Earthquake Magnitudes ------ 2.5 -111ethod of Study --------------------------------- 3 -FAULT EVALUATION CRITERIA AND GUIDELINES ---------------- 3.1 -Guidelines for Defining Recent Fault Displacement Criteria -------------------------- 3.1.1 -Regulatory Criteria ---------------------------- 3.1.2 -Guidelines for Identifying and Studying Faults with Recent Displacement -------------- 3.2 -Length-Distance Screening Criteria --------------- 4 -REGIONAL HISTORICAL SEISMICITY -------------------------- 4.1 -Plate Tectonic Setting --------------------------- 4.2 -Regional Seismicity and Seismic Gaps ------------- 4.3 -Historical Seismicity --------------------------- 4.3.1 -Shallow Benioff Zone --------------------------- 4.3.2 -Deeper Benioff Zone ---------------------------- 4.3.3 -Crustal Seismicity ----------------------------- Page 1 - 1 1 -1 1 - 3 1 - 4 1 -5 1 - 6 1 - 7 1 -8 1 -10 1 -12 1 12 1 -13 1 -14 2 - 1 2 - 1 2 - 3 2 5 2 -7 2 - 7 2 -14 2 -15 3 -1 3 -2 3 - 2 3 - 6 3 8 4 - 1 4 - 1 4 - 2 4 5 4 - 7 4 - 8 4 -10 TABLE OF CONTENTS (CONTINUED) 5 -TECTONIC MODEL--TALKEETNA TERRAIN ----------------------- 6 -REGIONAL GEOLOGIC SETTING OF THE TALKEETNA TERRAIN ------ 6.1 -Regional Geologic Setting ------------------------ 6.2 -Regional Surface Geology ------------------------- 7 -GEOLOGIC SETTING OF THE SUSITNA HYDROELECTRIC PROJECT REGION ---------------------------------------- 7.1 -Geologic Setting of the Project Area ------------- 7.1.1 -Bedrock ---------------------------------------- 7.1.2 -Structure -------------------------------------- 7.2 -Surface Geology of the Project Area ------------- 7.2.1 -Pleistocene and Holocene Deposits -------------- 7.2.2 -Glacial History-------------------------------- 8 -FAULTS AND LINEAMENTS ----------------------------------- 8.1 -Introduction------------------------------------- 8.2 -Classification System ---------------------------- 8.3 -Selection of Significant Features ---------------- 8.4 -Talkeetna Terrain Boundary Faults ---------------- 8.5 -Significant Features ----------------------------- 8.5.1 -Watana Site ------------------------------------- 8.5.2 -Devil Canyon Site ------------------------------- 9 -SHORT-TERM MICROEARTHQUAKE MONITORING PROGRAM ----------- 9.1 -Introduction ------------------------------------- 9.2 -Network Operation and Data Analysis -------------- 9.3 -Crustal Earthquake Sources ----------------------- 9.4 -Benioff Zone Seismicity -------------------------- 9.5 -Comparison of Susitna Project Area Attenuation with That of Comparable Tectonic Areas Worldwide ----------------------- 10 -RESERVOIR-INDUCED SEISMICITY (RIS) ---------------------- 10.1 -Introduction ------------------------------------ 10.2 -State-of-the-Knowledge in RIS ------------------- 10.2.1 -Temporal and Spatial Relationships------------ 10.2.2 -Relationship to Fault Reactivation ------------ 10.2.3 -Characteristics of a RIS Event ---------------- 10.3 -Potential for Reservoir-Induced Seismicity (RIS) at the Project Reservoirs --------------- 10.3.1 -Comparison with Worldwide Data Base ----------- 10.3.2 -Evaluation of Potential Occurrence ------------ 10.4 -Effect of RIS on Earthquake Occurrence Likelihood------------------------- 10.4.1 -Implications of RIS for Method of Reservoir Filling ------------------------ 10.4.2 -Potential for Landslides Resulting from Reservoir-Induced Seismicity ----------- 5 6 6 6 7 7 7 7 7 7 7 8 8 8 8 8 8 8 8 9 9 9 9 9 9 10 10 10 10 10 10 10 10 10 10 10 10 -1 -1 -1 -7 -1 -1 -1 -5 - 6 - 8 -12 -1 -1 - 2 - 4 -10 -17 -17 -28 -1 -1 -1 - 3 - 7 -11 -1 -1 - 3 - 7 - 9 -11 -11 11 -14 -18 -19 -20 TABLE OF CONTENTS (CONTINUED) 11 -PRELIMINARY MAXIMUM CREDIBLE EARTHQUAKES (PMCEs) -------- 11.1 -Distant Sources Outside the Talkeetna Terrain --- 11.1.1 -Sources Outside the Talkeetna Terrain --------- 11.1.2 -Talkeetna Terrain Boundary Sources ------------ 11.2 -Effect of Reservoir-Induced Seismicity on the Preliminary Maximum Credible Earthquakes ------ 12 -PRELIMINARY GROUND MOTION STUDIES ----------------------- 12.1 -Methodology for Estimating 12 .1.1 12 .1. 2 12 .1. 3 12.2 Earthquake Ground Motions --------------------- -Peak Ground Acceleration ---------------------- -Acceleration Response Spectra ----------------- -Duration of Strong Ground Shaking ------------- -Preliminary Estimates of Earthquake Ground Motions --------------------- 13 -CONCLUSIONS --------------------------------------------- 13.1 -Feasibility Conclusions ------------------------- 13.2 -Technical Conclusions -------------------------- 14 -PROPOSED 1981 STUDY PLAN -------------------------------- APPENDIX A -ANNOTATION AND DOCUMENTATION PROCEDURES FOR THE GEOLOGIC INVESTIGATION A.1 -Introduction -----------------------------------------A.2 -Fault and Lineament Annotation and Documentation A.2.1 A.2.2 A.2.3 A.2.4 Procedures ----------------------------------------- -Literature Review (Form SHP-2) --------------------- -Remotely Sensed Data (Form SHP-4) ------------------ -Assignment of Remote Sensing Code Numbers ---------- -Transfer of Lineaments Identified on Remotely Sensed Data to Base Maps ---------------- A.2.5 -Assignment of Map Code Numbers to Faults and Lineaments ----------------------------------- A.2.6 -Completion of the Fault and Lineament Data Summary Sheet (Form SHP-3) ----------------------- A.3 -Field Reconnaissance Study Documentation Procedures -- A.3.1 -Completion of Field Observation Documentation Sheet (Form SHP-6) ------------------------------- A.3.2 -Photography Documentation (Forms SHP-7 and SHP-8) -- A.3.3 -Completion of Fault and Lineament Index Sheet (Form SHP-5) ------------------------------------- 11 - 1 11 - 2 11 - 2 11 - 2 11 - 4 12 - 1 12 - 2 12 - 2 12 - 3 12 - 3 12 - 3 13 - 1 13 - 1 13 - 2 14 - 1 A - 1 A - 1 A - 2 A - 2 A - 4 A - 5 A - 7 A - 8 A -11 A -13 A -15 A -16 A -17 TABLE OF CONTENTS CONTINUED APPENDIX B -1980 MICROEARTHQUAKE NETWORK INSTALLATION, OPERATION, AND MAINTENANCE PROCEDURES B.1 -Site Selection --------------------------------------- B.2 -Instrumentation -------------------------------------- B.3 -Installation, Operation, and Record Changing --------- B.4 -Record Reading Procedures ---------------------------- 8.5 -Velocity Model --------------------------------------- B.6 -Location of Microearthquakes ------------------------- 8.7 -Earthquake Magnitude Determination Procedure --------- 8.8 -Focal Mechanisms -------------------------------------B.9 -Blasting Identification _______________ : _____________ _ APPENDIX C -HISTORICAL EARTHQUAKE CATALOG APPENDIX D -SUSITNA STUDY AREA MICROEARTHQUAKE CATALOG APPENDIX E -ESTIMATION OF PRELIMINARY MAXIMUM CREDIBLE EARTHQUAKES E.1 Introduction ----------------------------------------- E.2 -Fau1t Parameter Method--Magnitude versus Rupture Length ------------------------------------- E.3 -Results ---------------------------------------------- APPENDIX F -QUALITY ASSURANCE F.1-Responsibility, Authority, and Accountability-------- F.2 -Methods of Operation --------------------------------- F.3 -Documentation of Activities -------------------------- F.4 -Internal Review Procedures --------------------------- F.5 -Audits ----------------------------------------------- APPENDIX G GLOSSARY APPENDIX H -REFERENCES B -1 B -1 B - 2 B - 4 B - 5 B -7 B - 8 B -10 B -11 B -12 c -1 D -1 E - 1 E 1 E 3 E - 7 F - 1 F -1 F - 2 F - 5 F - 5 F - 8 G -1 H -1 LIST OF TABLES 3-1 Mean Relationship Between Fault Rupture Length and Earthquake Magnitude 3-2 Length-Distance Criteria for Identification of Faults and Lineaments for Preliminary Field Reconnaissance 8-1 Summary of Geologic Characteristics Used to Classify Candidate Features 8-2 Boundary Faults and Candidate Significant Features 8-3 Summary of Boundary Faults and Significant Features 10-1 Reported Cases of Reservoir-Induced Seismicity (RIS) 10-2 Reservoir-Induced Seismic Events with Maximum Magnitude of 5 or Greater B-1 Microearthquake Station Location and Operation Summary B-2 Velocity Model Used for 1980 Microearthquake Data Analysis C-1 Historical Earthquake Catalog D-1 1980 Microearthquake Catalog F-1 Project Peer Review and Internal Review Panel Members LIST OF FIGURES 1-1 Location Map 1-2 Project Location Map 2-1 Block Diagram of Various Fault Slip Components 2-2 Block Diagrams of Schematic Effects of Shifts Along a Reverse-Slip Fault 2-3 Block Diagrams of Schematic Effects of Shift Along a Normal-51 ip Fault 2-4 Block Diagrams of Schematic Effects of Shift Along a Strike-Slip Fault 2-5 Block Diagram of Relationship of a Fault Zone with Recent Displacement to a Fault Zone 2-6 1980 Seismic Geology Flow Diagram 3-1 Graph Showing the Relationship Between Earth- quake Magnitude and the Length of Aftershock Zones 3-2 Surface Rupture Zone Width Relationships 4-1 Plate Tectonic Map 4-2 Major Earthquakes and Seismic Gaps in Southern Alaska 4-3 Location Map of University of Alaska, U.S.G.S., and NOAA Seismograph Stations in Alaska 4-4 Historical Earthquakes of All Focal Depths in the Site Region from 1~04 through 1978 4-5 Historical Earthquakes of Focal Depth Greater Than 35 km in the Site Region From 1904 through 1978 4-6 Historical Earthquakes of Focal Depth Less Than 30 km in the Site Region From 1904 through 1978 4-7 Estimated Modified Mercalli Felt Intensities for the Earthquake of 27 August 1904 4-8 Estimated Modified Mercalli Felt Intensities for the Earthquake of 7 July 1912 LIST OF FIGURES (CONTINUED) 5-1 Talkeetna Terrain Model 5-2 Schematic Talkeetna Terrain Section 6-1 Geologic Time Scale 6-2 Talkeetna Terrain Bedrock Geology Map 6-3 Talkeetna Terrain Surface Geology Map 7-1 Project Area Bedrock Geology Map 7-2 Project Area Surface Geology Map 7-3 Location Map of Preliminary Quaternary Geology Studies 8-1 Field Classification of Candidate Features 8-2 Boundary Fault and Significant Feature Map for the Site Region 8-3 Watana Site Significant Feature Map 8-4 Devil Canyon Area Significant Feature Map 8-5 Devil Canyon Site Significant Feature Map 8-6 Aerial View of McKinley Strand of Denali Fault Near the Cantwell Glacier 8-7 Aerial View of Castle Mountain Fault (ADS-1) 8-8 View of Talkeetna Thrust Fault Location on the Susitna River 8-9 Aerial View of Susitna Feature (KD3-3) 8-10 Aerial View of Feature KD3-7 8-11 View of Fins Feature (KD4-27) at Tsusena Creek 8-12 Aerial View of Feature KCS-5 8-13 View of Oxidized~ Sheared Zone along Feature KDS-2 8-14 Aerial View of Feature KDS-3 LIST OF FIGURES (CONTINUED) 8-15 View of Feature KD5-9 8-16 Aerial View of Feature KD5-12 8-17 Aerial View of Feature KD5-42 8-18 Aerial View of Feature KD5-43 8-19 Aerial View of Feature KD5-44 8-20 Aerial View of Feature KD5-45 9-1 Shallow (Focal Depth <30 km) Local Earthquakes Located From 28 June Through 28 September 1980 9-2 Deep (Focal Depth >30 km) Local Earthquakes Located from 28 June through 28 September 1980 9-3 Frequency-Magnitude Plots for Earthquakes in Microearthquake Study Area From 28 June to 28 September 1980 9-4 Number of Located Earthquakes Per Day 9-5 N45DE Sectional View of Microearthquake Clusters One and Two 9-6 N45°W Sectional View of Microearthquake Clusters One and Two 9-7 Composite Focal Mechanism Plots of Microearthquake Clusters One and Two ~-8 Focal Mechanism Plots of Selected Microearthquakes (Focal Depth < 30 km) 9-9 Cross-Section of Crustal and Benioff Zone Microearthquakes Located Within the Network 9-10 Composite Focal Mechanism Plots of Selected Microearthquakes (Focal Depth > 30 km) 10-1 Plot of Water Depth and Volume for Worldwide Reservoirs and Reported Cases of RIS 10-2 Diagrams Showing Effective Stress Relationships 10-3 Plot of Time Between Impoundment and First Suspected RIS Event 10-4 Plot of Time Between Impoundment and Largest Suspected. RIS Event LIST OF FIGURES CONTINUED 10-5 Plot of Magnitude of Largest RIS Event Versus Time After Impoundment for Accepted RIS at Deep, Very Deep, and/or Very Large Reservoirs 10-6 Plot of Magnitude of Largest RIS Event Versus Time to First RIS Event at Deep, Very Deep~ and/or Very Large Reservoirs 10-7 Probability of RIS Occurrence with Maximum Magnitude > M for Deep, Very Deep, and/or Very Large Reservoirs' 10-8 Plot of Variation of RIS Probability with Delay to First Event 10-9 Plot of Variation of RIS Probability with Different Stress Regimes for Deep, Very Deep, and/or Very Large Reservoirs 10-10 Plot of Variation of RIS Probability with Different Geologic Settings for Deep, Very Deep, and/or Very Large Reservoirs 12-1 Preliminary Mean Response Spectra at the Watana Site for Preliminary Maximum Credible Earthquakes on Known Faults with Recent Displacement 12-2 Preliminary Mean Response Spectra at the Devil Canyon Site for Preliminary Maximum Credible Earthquakes on Known Faults with Recent Displacement A-1 Flow Diagram 'Of Documentation Procedures A-2 Reference Documentation Sheet (Form SHP-2) A-3 Remote Sensing Lineament ~orksheet (Form SHP-4) A-4 U-2 Photography Flightline Coverage Map A-5 Landsat Imagery Coverage Map A-6 Fault and Lineament Data Summary Sheet (Form SHP-3) A-7 Field Observation Documentation Sheet (Form SHP-6) LIST OF FIGURES CONTINUED A-8 Photo Log (Form SHP-7) A-9 Fault and Lineament Photo Log (Form SHP-8) A-10 Fault and Lineament Index Sheet (Form SHP-5) B-1 Microearthquake Station Array B-2 Daily Operation Summary of Microearthquake Stations B-3 Smoked Paper Data Sheet B-4 Microearthquake Preliminary Reading Sheet F-1 Peer Review Documentation DEFINITION OF KEY TERMS Site Region: Project Area: Devil Canyon Area: Devil Canyon Site: Devil Canyon Reservoir: Watana Area: Watana Site: Watana Reservoir: The area within a 62-mile (100-km) radius about either site. This generally includes the Devil Canyon and Watana areas and the region in between. The area within a 6-mile (10-km) radius about the Devil Canyon site. The presently proposed location of the Devil Canyon Dam and related facilities. The area of the Susitna River upstream from the proposed Dev i 1 Canyon site which will be inundated by impoundment by the dam. The area within a 6-mile (10-km) radius about the Watana site. The presently proposed location of the Watana Dam and related facilities. The area of the Susitna River up- stream from the proposed Watana site which will be inundated by impoundment by the dam. FINITION OF KEY TERMS CONTINUED Microearthquake Study Area: The area in which microearthquake monitoring was conducted in 1980. The boundaries are 62.3° to 63.3° north latitude and 147.5° to 150.4° west longitude. ACKNOWLEDGMENTS The Woodward-Clyde Consultants personnel who participated in the geo- logical portion of the seismic geology investigation included: George Brogan, Tom Freeman, Paul Guptill, Ram Kulkarni, George Linkletter, Jon Lovegreen, Ron Mees, Jan Rietman, Ray Sugiura, John Waggoner, Ken Weaver, Dennis Welsch, and Jerry Williams. Dr. Norm Ten Brink of Grand Valley State College, Michigan, assisted with the preliminary Quaternary geology studies. The Woodward-Clyde Consultants personnel who participated in the seismo- logical portion of the seismic geology investigation were: Jim Agnew, Jean Briggs, Jim Cullen, John Hobgood, and William Savage. Jason McBride and Richard Thompson of Woodward-Clyde Consultants, and Milton Mayr, Dianne Marshall, Cole Sonafrank, and Rodney Viereck of the University of Alaska Geophysical Institute assisted with the micro- earthquake operation. The earthquake engineering portion of the investigation was conducted by John Egan and Maurice Power of Woodward- Clyde Consultants .. Discussions were held with members of the Alaska Geological Observatory, the Alaska Geophysical Institute, the Lamont-Doherty Geological Survey, the University of Alaska, and the U. S. Geological Survey. Dr. Ulrich Luscher was the prinicipal-in-charge of the investiga- tion; George Brogan assisted by Jon Lovegreen was Project manager. Dr. William Savage directed the seismology study and Maurice Power directed the earthquake engineering study. Project peer review was provided by Dr. Robert Forbes, Professor Emeritus of Geology of the University of Alaska (geology); and Dr. I. M. Idriss, (earthquake engineering), Dr. Duane Packer (geology), Dr. William Savage (reservoir-induced seismicity); and Tom Turcotte (seis- mology) of Woodward-Clyde Consultants. Aircraft support was provided by Akland Helicopter Inc. and ERA Helicop- ters Inc. and was arranged by Acres American Inc. Lodging and logistical support in the field was arranged by Acres American Inc. This report was prepared by Woodward-Clyde Consultants. Technical support and typing was provided by Carole Wilson assisted by Barbara Beldon, Esther Martin, and Hazel Whittaker. Illustrations were prepared by Arlene Pa.damada, assisted by Dennis Fisher. Robyn Sherrill, and Chairoach Siripatanapaibul. Technical editing was done by Karen Lundegaard. Printing and binding of the report was done by Continental Graphics. 1 -SUMMARY 1.1 -Project Description The Susitna Hydroelectric Project as currently proposed involves two dams and reservoirs on the Susitna River in the Talkeetna Mountains of southcentral Alaska. The Project is approximately 50 miles (80 km) northeast of Talkeetna, Alaska and 118 miles (190 km) north-northeast of Anchorage, Alaska (Figures 1-1 and 1-2). The downstream dam at Devil Canyon (62.8° north latitude, 149.3° west longitude) is currently being considered as an arch dam approximately 635 feet (194m) high. It would impound a 28-mile-(45-km-) long reservoir with a capacity of approx- imately 1,050,000 acre feet (1,296 x 106m3). The upstream dam, Watana (62.8° north latitude, 148.6° west longitude), is currently being considered as an earthfill or rockfill dam, approximately 810 feet (247 m) high. It would impound a 54-mile-(87-km-) long reservoir with a capacity of approximately 9,624,000 acre feet (11 ,876 x 106m3). These dimensions are approximate and subject to revision during design of the project. Collectively, the proposed dams and related structures will be referred to as the Project. This report is part of a feasibility study being managed and conducted by Acres American Inc. for the Alaska Power Authority. The investiga- tion conducted to date has involved the first year of a planned two-year study (1980 and 1981). The purpose of this report is to summarize the results of the seismic geology, seismology, and earthquake ground motion investigation conducted during the 1980 study. The primary objectives of this investigation have been to identify faults which have the potential for surface rupture through the Project and to make a preliminary estimate of earthquake ground motions which 1 - 1 would be applicable to preliminary feasibility level decisions for the project. Using the results of the investigation to date. a study plan for the 1981 investigation has also been developed. The 1980 investigation has included: review of available geologic and seismologic literature and data; monitoring of microearthquake activity for three months within approximately 30 miles (48 km) of either proposed darn site with a 10-stat ion microearthquake network; a pre- liminary review of the potential for reservoir-induced seismicity; interpretation of existing remotely sensed, data; a 10 person-month geologic field reconnaissance of mapped faults and lineaments within 62 mi1es (100 krn) of the Project; analysis and interpretation of these data; and a preliminary estimate of potential earthquake ground motions for the project. The review of geologic and seisrnologic data and the interpretation of remotely sensed data were conducted in the winter and spring of 1980. The microearthquake monitoring and geologic field reconnaissance were conducted in the summer and early fall, 1980. In the winter of late 1980, the ground motion studies were conducted and analysis of the data, including the preliminary assessment of the potential for reser- voir-induced seismicity~ was completed. Approximately 25 geologists, seismologists~ and earthquake engineers have had a direct involve- ment with the study to date. This section summarizes the results presented in this report; thus~ full development of concepts, data, and bases for interpretations have been abstracted or deleted in the interest of brevity. Consequently~ concepts, interpreta.t ions~ and conclusions are intended to be read and understood within the context of corresponding sections in the text. 1 2 1.2 -Conceptual Approach According to present understanding of plate tectonics, the earth's lithosphere, which contains the brittle 12 to 19 miles (20 to 30 km) or so of more rigid crust, overlies the denser and more viscous mantle. Observed major horizontal movements of the crustal plates are considered to be related to, or caused by, thermal convective processes within the mantle. Within this plate-tectonic framework, faults that have the poten- tial for generating earthquakes have had recent displacement and may be subject to repeated displacements as long as they are in the same tectonic stress regime. In regions of plate collision such as Alaska, the tectonic stress regime is the result of one plate being subducted, or underthrust, beneath the adjacent plate. Within this environment, primary rupture along fault planes can occur: within the downgoing plate where it is decoupled from the upper plate; along the interface between the upper and lower plates where they move past each other; and within the overriding plate. In the site region, faults with recent displacement are present in the overriding (upper) plate and at depth in the downgoing plate where it is decoupled from the upper plate. Faults with recent displacement in the downgoing plate and in the upper plate can generate earthquakes which result in ground mot ions at the surface. These earthquakes are considered for seismic design purposes. The faults in the downgoing plate are considered not to have the potential for surface rupture. In the upper plate, if the rupture that occurs on these faults is relatively small and relatively deep. then rupture at the ground surface is likely not to occur. If the rupture along the fault plane is at sufficiently shallow depth and is suf- ficiently large, then surface rupture can occur. 1 - 3 Woodward-Clyde Consultants Criteria for establishing guidelines to define what is considered 11 recent displacement 11 have been developed by Acres American Inc. and are presented in Section 3. According to these criteria, faults that have been subject to surface displacement within approximately the past 100,000 years are classified as having recent displacement. Inherent with this concept of 11 fault with recent displacement 11 is the basic premise that faults without recent displacement will not have surface rupture nor be a source of earthquakes. Faults without recent displacement (as determined during this investigation) are considered to be of no additional importance to Project feasibility and dam design. 1.3 -Method of Study The application of the 11 fault with recent displacement 11 concept for this investigation involved: (a) Identification of all faults and lineaments in the site region that had been reported in the literature and/or were observable on remotely sensed data. (b) Selection of faults and lineaments of potential signific~nce in developing design considerations for the Project, from tlie stand- point of seismic source potential and/or potential surface rupture through a site. These faults and lineaments were selected using the length-distance criteria described in Section 3. These 216 faults and lineaments were designated as candidate features. (c) Evaluation of the 216 candidate features during the geologic field reconnaissance studies. On the basis of this field work, the microearthquake data, and application of the preliminary sig- nificance criteria described in Section 8, 48 faults and lineaments 1 -4 were designated as candidate significant features. These features were su~jected to additional evaluation using refined analyses, as described in (d) below, to select those features of potential significance to Project design considerations. (d) Refinement of the evaluation process, using the significance criteria which are summarized in Section 1.6. On the basis of this evaluation, 13 significant features were selected for continued studies in 1981. 1.4 -Tectonic Model An understanding of the regional geologic and tectonic framework is essential for: the assessment of fault activity; estimation of pre- liminary maximum credible earthquakes; evaluation of the potential for surface fault rupture; and evaluation of the potential for reservoir- induced seismicity. The site region is located within a tectonic unit defined here as the Talkeetna Terrain. The Terrain boundaries are the Denali-Totschunda fault to the north and east, the Castle Mountain fault to the south, a broad zone of deformation with volcanoes to the west, and the Benioff zone at depth. All of the boundaries are (or contain) faults with recent displacement except for the western boundary which is primarily a zone of uplift marked by Cenozoic age volcanoes. The Terrain is part of the North American plate (as discussed in Section 5 and shown in Figure 5-1). Preliminary results of this study suggest that the Talkeetna Terrain is a relatively stable tectonic unit with major strain release occurring along its boundaries. This conclusion is based on: the evidence for recent displacement along the Denali-Totschunda and Castle Mountain 1 - 5 faults and the Benioff zone; the absence of major historical earth- quakes within the Terrain; and the absence of faults within the Terrain that clearly have evidence of recent displacement. As discussed below, none of the faults and 1 ineaments observed within the Talkeetna Terrain were observed to have strong evidence of recent displacement. Strain accumulation and resultant release appears to be occurring primarily along the margins of the Terrain. Some compression-related crustal adjustment within the Terrain is probably occurring as a result of the proposed plate movement and the stresses related to the subduc- tion zone. This tectonic model is preliminary. It is intended to serve as a guide to understanding tectonic and seismologic conditions in the site region. As additional data are obtained, the model may be refined; however, these refinements are not expected to result in major changes in the model or its interpretations. 1.5 -Candidate Significant Features As discussed in Section 1.3, a total of 48 candidate significant fea- tures were identified in the site region on the basis of the initial length-distance screening criteria, their proximity to the site, their classification in the field, and application of preliminary significance screening criteria. These features and their characteristics are summarized in Table 8-2. Candidate significant features are those faults and lineaments which on the basis of available data at the end of the field reconnaissance, were considered to have a potential effect on Project design. Subsequent evaluation, using a refined, systematic ranking methodology, resulted in the identification of the significant features discussed below in Section 1.6. 1 - 6 1.6 -Significpnt Features The 48 candidate significant features were subsequently evaluated by making detailed analyses regarding their seismic source potential and surface rupture potential at either site. For the evaluation of seismic source potential, the analyses included: an assessment of the likelihood that a feature is a fault with recent displacement; an esti- mation of the preliminary maximum credible earthquake that could be associated with the feature; and an evaluation of the peak bedrock ac- celerations that would be generated by,the preliminary maximum credible earthquake at either site. To evaluate the potential for surface rupture at either dam site. the analyses included: an assessment of the 1 ikel ihood that a feature is a fault with recent displacement; an assessment of the likelihood that a feature passes through either site; and an evaluation of the maximum amount of displacement that could occur along the feature during a single event (e. g., the preliminary maximum credible earthquake). Our evaluation of the 48 candidate significant faults, applying the judgments described above, resulted in the selection of 13 features, designated significant features, that should have additional studies to understand and more fully evaluate their significance to the Project. Of these 13 features. four are in the vicinity of the Watana site including the Talkeetna thrust fault {KC4-1). Susitna feature (K03-3), F.ins feature (KD4-27), and lineament KD3-7 Nine of the features are in the vicinity of the Devil Canyon site including an unnamed fault (designated KDS-2), and lineaments KC5-5~ KDS-3, KD5-9. KDS-12, KDS-42, KD5-43. KDS-44, and KD-45 (the alpha-numeric symbol {e. g .• KC4-1) has been assigned to each fault and lineament using procedures discussed in Appendix A). The characteristics of these features are described in Section 8.5 and their locations are shown in Figures 8.2 through 8.5. 1 - 7 Woodward-Clyde Consultants None of these s ignficant features are known to be faults with recent displacement; rather, the significant features are those for which additional data are required to preclude recent displacement along a fault. The significant features are not known to be accepted seismic sources with recent displacement; however, additional data are needed to confirm this judgment. 1.7 -Seismicity Historical earthquake activity within 200 miles (322 km) of the Project is associated with displacement along crustal faults in the upper plate (as discussed in Section 1.2 above) and with the subducting (downgoing) plate. The largest earthquake within 200 miles (322 km) of the Project is the 1964 Prince William Sound earthquake of magnitude (Ms) 8.4. This earthquake occurred outside the Talkeetna Terrain on the interface between the Wrangell Block in the North American Plate and the Pacific Plate (Figure 4-1); the associated rupture and deformation extended to within approximately 88 miles (140 km) of the Project. Within the site region (62 miles (100 km) from the Project), the level of seismicity on the Benioff zone is at least several times greater than that of the crustal region. The larger historical earthquakes (Ms > 5) that have occurred in the crust are apparently associated with known major faults with recent displacement, such as the Oenal i fault and the Castle Mountain fault. Most of these earthquakes, however, occurred prior to the operation of the regional seismographic network that began in 1964, so the accuracy of locations and focal depths is low, with uncertainties as large as 31 to 62 miles (50 to 100 km). The two largest, possibly crustal earthquakes that may have had epicenters in the site region, occurred in 1904 (Ms 7-3/4) and 1912 (Ms 7.4). If these events occurred in the crust, they are both likely to have occurred on the Denali fault which is at a closest distance of 40 miles (64 km) to the Project. 1 - 8 Within the site region, the largest reported earthquake (magnitude (Ms) 6-1/4) ,occurred on 3 July 1929. The epicenter and focal depth uncertainty of this event (~ 31 miles (50 km)) are great enough to suggest that it may have occurred on the Benioff zone at a depth of 31 to 43 miles (50 to 70 km). During three months of mid-1980, a ten-station microearthquake array was operated to study the area within 30 miles (48 km) of the Project. More than 260 earthquakes in the magnitude (ML) range 0.0 to 3.7 were analyzed. The discussion below summarizes the results. Earthquake activity clearly delineates two seismic zones. The upper zone of crustal activity occurs predominantly in the depth range 5 to 12 miles (8 to 20 km). The lower zone of activity defines a northwestward dipping zone (the Benioff zone) at a depth of 25 miles (40 km) in the southeast to 50 miles (80 km) in the northwest portion of the micro- earthquake study area. The Benioff zone is approximately 6 to 9 miles (10 to 15 km) thick and is characterized by widely distributed seis- Within the Benioff zone. no lineations or other prominent features were observed. The seismicity appears to occur throughout the does not define a single interplate interface. Focal mechanism interpretations for the Benioff zone suggest that the primary mode of deformation is due to high-angle normal faulting produced by down-dip extensional faulting within the plate. During the three-month period of monitoring, 13 earthquakes of magnitude · (ML) 3.0 and larger were located in the Benioff zone. This level of acti~ity is about ten times greater than that recorded for the shallow (crustal) zone. The slope of the magnitude-frequency graph for the Benioff zone is 0.68, similar to that for many areas worldwide. This curve suggests a relatively low number of larger earthquakes compared to smaller earthquakes. These results are consistent with the historical seismicity record. 1 - 9 The crustal earthquake activity was found to be generally confined to the geographic area of the Talkeetna Mountains. There were rela- tively few events occurring at depths shallower than 5 miles (8 km) or deeper than 12 miles (20 km). No seismic activity that appeared to be associated with the crust was deeper than 19 miles (30 km). The level of seismicity within the crustal zone within 30 miles (48 km) of the Project is very low, about one-tenth of the Benioff zone activity. The slope of the associated magnitude frequency curve is 1.48. Map views and cross-sections of the shallow, earthquakes were examined for possible spatial associations with mapped faults and lineaments. No associations were identified. Two clusters of small microearthquakes were located 16 to 22 miles (25 to 35 km) south of the Project at a depth of 9 to 12 miles (15 to 20 km). These clusters occurred within 12 miles (20 km) of the surface trace of the Talkeetna thrust fault; however, on the basis of results obtained to date, they do not appear to be associated with the Talkeetna thrust fault or any other surface feature. These clusters are related to extremely small-scale rupture on faults at depth in the crust. The rupture plane is too small and too deep to cause surface rupture. Focal mechanism studies of crustal earthquakes within approximately 30 miles (48 km) of the Project indicate the occurrence of a regionally uniform west-northwest to east-southeast oriented horizontal compres- sional stress field. This stress field is producing thrust or strike- slip movement on small, features distributed in the lower crust. 1.8 -Reservoir-Induced Seismici The reservoirs which will be impounded behind the proposed dams will be very deep (greater than 492 feet (150m)). In the case of Devil Canyon, the reservoir will be large, with a volume greater than 1 x 106 acre 1 -10 {1,234 x 106m3); in the case of Watana., it will be very large, a volume greater than 8.1 x 106 acre feet (10 9 000 x 1o6m3). of the proximity of the two reservoirs to each other, they will one hydrologic unit which will be very deep and very large. that the proposed combined hydrologic unit will be very deep and large, the potential for reservoir-induced seismicity (RIS) has estimated by evaluating reservoir-induced seismicity at other deep, deep~ and very large reservoirs. The results of this comparison the likelihood that a reservoir-,induced event of any size u~ing microearthquakes) will occur at the proposed reservoir is 0.9 scale of 0 to 1). the likelihood of a reservoir-induced event is high~ it is impor- to understand what the maximum earthquake is likely to be for the how the reservoir will affect the likelihood that a -large (magnitude (M 5 ) > 5) event will occur. Previous (Packer. Lovegreen and Born. 1977; Packer and others, 1979) have data which support the concept that reservoirs can trigger s by means of pore pressure increases or incremental increase Because reservoirs act as triggering mechanisms. they are expected to cause an earthquake larger than that which could occur a given region 11 natura11y .11 Rather~ the reservoirs are expected have a potential affect on the length of time between events and ibly on the location of the event. Thus~ if the tectonic and ogic setting of a region is known and if the maximum earthquake adequately defined. the maximum size of a reservoir-induced can be identified. reviewed for this investigation suggest that reservoir-induced magnitude (Ms) larger than 5 occur where faults with displacement lie within the hydrologic regime of the reservoir. ts with recent displacement are known to be present within the 1 -11 hydrologic regime of the proposed reservoirs. Consequently, the 1 ikel ihood of a reservoir-induced earthquake of magnitude (Ms) greater than 5 is considered to be low. However, if studies conducted during 1981 demonstrate that faults with recent displacement are present within the hydrologic regime of the reservoir, then the 1 ikel ihood of a RIS event of magnitude (Ms) greater than 5 will need to be re-evaluated. 1.9-Preliminary Maximum Credible Earthquakes (PMCEs) Preliminary maximum credible earthquakes (PMCEs) have been estimated for crustal faults with unequivocal evidence of recent displacement and for the Benioff zone. The PMCEs for the crustal faults have been estimated using the fault rupture length relationships of Slemmons (1977) and the rupture area relationship of Wyss (1979). The higher (more conserva- tive) of the two values has been used where the two relationships provided different values. The PMCE for the Benioff zone was estimated using historical activity. The PMCE estimated for the Denali fault and Benioff zone is magnitude (Msl 8.5. For the Castle Mountain fault, it is magnitude (Msl 7.4. 1.10-Preliminary Ground Motion Studies A preliminary assessment was made of earthquake gn::~und motion at the sites. The characteristics of ground motions addressed in these studies included peak horizontal ground acceleration, response spectra, and the duration of strong shaking. The assessment was made for preliminary maximum credible earthquakes on the known faults with recent displace- ment in the site region. The results of this assessment are presented in Section 12. 1 -12 1.11 -Conclusions Two sets of conclusions have been drawn from the results of the inves- tigation conducted to date. One set, designated feasibility conclus- .ions, are those considered important to evaluate the preliminary feasibility of the Project. The second set, designated technical conclusions, are those related to the scientific data collected. Both sets of conclusions are discussed in Section 13 and form the basis for the proposed 1981 study plan (summarized below in Section 1.12). The feasibility conclusions are summarized in this section; they include: (a) No faults with known recent displacement (displacement in the last 100,000 years) pass through or adjacent to the Project sites. (b) The faults with known recent displacement closest to the Project sites are the Denali and Castle Mountain faults. These faults, and the Benioff zone associated with the subducting Pacific Plate (at depth below the Project site). ~re considered to be accepted seismic sources. (c) Preliminary maximum credible earthquakes for the Denali and Castle Mountain faults and the Benioff zone have been estimated as a: magnitude (Ms) 8.5 earthquake on the Denali fault occurring 40 miles (64 km) from the Devil Canyon site and 43 miles (70 km) from the Watana site; magnitude (Ms) 7.4 earthquake on the Castle Mountain fault occurring 65 miles ( 105 km) from the Devil Canyon site and 71 miles (ll5 km) from the Watana site; and magnitude (Ms) 8.5 earthquake on the Benioff zone occurring 37 miles (50 km) from the Devil Canyon site and 31 miles (50 km) from the Watana site. (d) Within the site region, 13 faults and lineaments have been judged to need additional investigation to better define their potential 1 -13 affect on Project design considerations. These 13 faults and lineaments (designated significant features) were selected on the basis of their seismic source potential and potential for surface rupture through either site. Four of these features are in the vicinity of the Watana site and nine are in the vicinity of the Devil Canyon site. (e) At present, the 13 significant features are not known to be faults with recent displacement. If additional seismic geology studies show that any of these features is a fault with recent displacement, then the potential for surface rupture through either site and the ground motions associated with earthquakes on such a fault will need to be evaluated. (f) Preliminary estimates of ground motions at the sites were made for the Denali and Castle Mountain faults and the Benioff zone. Of these sources, the Benioff zone is expected to govern the levels of peak horizontal ground acceleration, response spectra, and duration of strong shaking. The ground-motion estimates are preliminary in nature and do not constitute criteria for design of project facilities. The site ground-motion estimates will be made final and the design criteria will be developed as part of the next phase of study. 1.12 Proposed 1981 Study Plan The proposed study plan is designed to provide additional data on the seismologic setting of the Project, on the. geologic characteristics of the 13 significant features, and for earthquake ground motion· studies. These data are needed: to evaluate faults with crustal sources of seismicity; to refine the evaluation of reservoir-induced seismicity; to obtain additional data on recent geologic units and morphologic surfaces 1 -14 that can be used for assessing the recency of fault displacement; and to evaluate whether or not the significant features are faults with recent displacement (and, if they are, to provide as much information as possible on the recurrence intervals, amount of displacement, and maximum credible earthquake). In addition, the study plan will incor- porate the results of the geologic investigation in a refined analysis of ground motions at the sites and will develop ground motion design criteria. ~he proposed study plan is expected.to be evolutionary in nature. Therefore, the details of the plan, presented in Section 14 and sum- marized below 9 may change during the course of the 1981 stud{es. The p 1 an is to: (a) Conduct a detailed Quaternary geology investigation. (b) Conduct field geologic studies of the 13 significant features. These studies will include additional air photo analysis and field mapping in appropriate locations. These studies may also include test pits, trenches, geophysical traverses, borings, and age dating. (c) Obtain and analyze low-sun angle aerial photography around both sites and along portions of the Talkeetna thrust fault and Susitna feature. (d) Conduct calibration studies along faults with recent displace- ment (e. g., either the Denali or Castle Mountain faults). The calibration can include field mapping. air photo analysis, and trenching. (e) Design a program manual for future seismologic network monitoring. 1 -15 (f) Re-evaluate the estimated potential for reservoir-induced seis- micity using the data obtained from the other portions of the 1981 study plan. (g) Finalize the ground-motion estimates for the Project (after the seismic geology field studies are performed to assess the seismic activity of the significant features). (h) Develop project earthquake ground-motion design criteria based on the results of the ground-motion evaluations. 1 -16 Gold Creek® ®Talkeetna DEVIL .CANYON SITE I WATANA SITE I 0 NOTE 1. Physiographic areas after Wahrhaftig (1965). LOCATION MAP 10 20 30 40Miles 0 10 20 30 40 50 Kiklmeters FIGURE 1-1 c? Butte Lake Stephan j'1'9°DWARD-CLYDE CONSULTANTS 14658A December 1980 Brooks Range 't;l'"~· . r:.o"" (c.<C-6.' I I ~I ALASKA Fairbanks\ CANADA I Ra:ge I D AREA SHOWN ' -IN DETAIL j "c,.,liBaciJ ' Anc~ 111rs.l-"\.. ,-. "'"" G"lf o< AIM<o '' ~~ ! NOTE 1. 0 Proposed reservoir configuration after U.S. Army Corps of Engineers ( 1979). PROJECT LOCATION MAP 5 10 15 20 Miles ~0~~~~1[0===20E~~~3?0 Kilometers FIGURE 1-2 2.1 -Project Description and Location Actording to present conceptual plans the Susitna Hydroelectric Project ('referred to hereafter as the Project) includes two dams and reservoirs in the Ta 1 keetna Mountains of south-centra 1 A 1 ask a (Figure 1-1). The present study to evaluate the feasibility of the Project was authorized bY the Board of Directors of the Alaska Power Authority (APA) on 2 1979. Acres American Inc. (AAI) was selected by the Alaska conduct the feasibility study. A Plan of Study (POS) AAI which identified the scope of services to be ted for the feasibility study (Acres American Inc., 1980). The of the feasibility study are to: Establish technical, economic, and financial feasibility of the Project to meet future power needs of the Railbelt Region of the State of Alaska; Evaluate the environmental sequences of designing and constructing the Susitna Project; and File a complete 1 icense application with the Federal Energy Regulatory Commission. -Clyde Consultants is one of a six-member team of consultants assemb 1 ed by AAI to meet the objectives of the study. The objectives and scope of participation in the feasibility study by Woodward-Clyde Consultants are described below in Sections 2.2 and 2.3. 2 - 1 The Project is located on the Susitna River, 50 miles (80 km) north- east of Talkeetna, Alaska, in the Talkeetna Mountains (Figures 1-1 and 1-2). The Devil Canyon site will be located at river mile 133 (62.8" north latitude, 149.3" west longitude); the Watana site will be located at river mile 165 (62.8" north latitude, 148.6" west longitude). This report encompasses the region within 62 miles (100 km) of either site. Thus, the Project site region includes the Talkeetna Mountains, the north-central portion of the Alaska Range, and portions of the Susitna and Copper River lowlands (Figure 1-1). The Project, as presently planned, involves two dams on the Susitna River (Figures 1-1 and 1-2). Downstream will be the Devil Canyon site which is presently planned to include a concrete arch dam having a structural height of approximately 635 feet (194 meters) with an estimated maximum water depth of 545 feet (166 meters). The impounded reservoir will be approximately 28-miles long (45 km) with a storage capacity of approximately 1,050,000 acre feet (1,296 x 106 m3). Up- stream will be the Watana site which is presently planned to include an earthfill or rockfill dam having a structural height of approximately 810 feet (247 meters) with an estimated maximum water depth of 725 feet (449 m). Its impounded reservoir will be approximately 54 miles (87 km) long with a storage capacity of 9,624,000 acre feet (11,876 x 106 m3) (U. S. Army Corps of Engineers, 1978). A transmission line, approximately 365 miles long (588 km), is planned to connect the power plants at the dam sites with existing transmission 1 ines. Several tunnel alignments from the Watana site to the vicinity of the Devil Canyon site are being considered on a preliminary basis. However, no conceptual details are available on the tunnel alternative at the time of this report. 2 -2 -Objectives responsibility of Woodward-Clyde Consultants for the Project feasi- bility study is defined in the Plan of Study (POS) prepared by AAI and by the Alaska Power Authority in February, 1980. The objectives POS are to: Determine the earthquake ground motions which will provide the seismic design criteria for major structures associated with the Project; Undertake preliminary evaluations of the seismic stability of proposed earth-rockfill and concrete dams; Assess the potential for reservoir-induced seismicity and land- slides; and Identify soils which are susceptible to seismically induced failure along the proposed transmission line and access routes. series of subtasks were identified to meet these overall task objec- The subtasks were established to provide the geologic, seismo- and earthquake engineering data needed to assess the feasibility Project. The subtasks and their corresponding objectives are: No. Subtask Title Review of Available Data Short Term Seismology Objective To acquire, compile, and review exis- ting data and to identify the earth- quake setting of the Susitna River. To establish an initial monitoring system, obtain and analyze basic seis- mologic data on potential earthquake sources within the Susitna River area, and to supply information required to imp 1 ement a more thorough 1 ong -term monitoring program. 2 - 3 4.06 4.07 4.08 Evaluation and Reporting Preliminary Ground Motion Studies Preliminary Analysis of Dam Stability To evaluate the potential for the pass i b 1 e future occurrence of reser- voir-induced seismicity (RIS) in the Project area. To select and interpret available remote sensing imagery to identify topographic features that may be associated with active faulting. To perform a reconnaissance investi- gation of known faults in the Susitna River area and of 1 i neaments that may be faults, to identify active faults, and to establish priorities for more detailed field investigations. To complete a preliminary evaluation of the seismic environment of the pro- ject, to define the earthquake source parameters for earthquake engineering input in design, and to document stud- ies in reports suitable for use in de- sign studies. To undertake a preliminary estimate of the ground motions (ground shaking) to which proposed Project facilities may be subjected during earthquakes. To make preliminary evaluations of the seismic stability of proposed earth, rockfill, and/or concrete dams during maximum credible earthquakes. The results of subtasks 4.01 through 4.05 are presented in this report (as part of subtask 4.06) and have been used to provide input to sub- task 4.07. This latter subtask addresses objective (a) and is discussed in Section 12. Limited consultation has been provided by Woodward-Clyde Consultnats to Acres for Objective (b) and is not included as a part of this report. Objective (c) is addressed by subtask 4.03, with results presented in Section 10. Objective (d) is scheduled to be evaluated in 1981; consequently, it has not been addressed during this investigation. 2 - 4 It should be emphas'ized that the results presented in this report have been developed solely for the purpose of evaluating Project feasibility. These results are subject to revision after completion of 1981 studies and therefore are not intended for use in final dam design considera- The data provided by this report are expected to be used in the applica- tion for the Federal Energy Regulatory Commission (FERC) license and in document at ions submitted to the U. S. Anny Corps of Engineers and the State of Alaska. This application will be made by Acres American Inc. on behalf of the Alaska Power Authority. -Scope 1980 study, as part of a planned two-year investigation and as sum- in this report, was designed and conducted to provide data for design feas ib i1 ity considerations. After project feasibility as been satisfactorily established, the 1981 study will evaluate spe- ific features and seismic conditions pertinent to seismic design. In this report, the work conducted during the first year will be referred to by the term "study.11 The term 11 investigation 11 will be used for the The multidisciplinary approach being utilized for this investigation involves an interactive team of structural geologists, Quaternary geolo- gists, seismologists, and earthquake engineers. Their task is the analysis of potential seismic sources, recency of fault displacement, and surface rupture potential. The subtask objectives (Section 2.2) incorporate this approach into a detailed scope and work plan. The following discussion summarizes the implementation of that detailed scope for subtasks 4.01 through 4.08. 2 - 5 The scope of those subtasks included: (a) the compilation of information for all faults and lineaments reported in the literature within 62 miles (100 km) of either dam site, for major faults with recent displacement in or adjacent to the site region, and for all lineaments interpreted by Wood- ward-Clyde Consultants which have morphologic relationships that may be fault related; (b) the compilation of historic earthquake data which could then be used to understand the seismic setting of the Project and to better define differences in the seismic ch aracteri st i cs between crustal earthquakes and the Benioff zone; (c) a geological field study to ascertain, on a reconnaissance level, which features in the site region are~ or potentially are, faults with recent displacement; (d) the install at ion and operation of a 10-stat ion mi croearthquake network within a 30-mile (48-km) radius about each proposed site to monitor seismicity in the vicinity of the sites, to provide information on crustal sources of seismicity and the depth to the Benioff zone. and to provide information on attenua- tion characteristics associated with crustal and Benioff zone sources; (e) a preliminary comparison of the depth, volume, and geologic char- acteristics of the proposed reservoirs with those of other reser- voirs that are deep, very deep~ and/or very large (including those with accepted cases of reservoir-induced seismicity) in order to make a preliminary estimate of the likelihood of reservoir-induced seismicity and of the likelihood that an earth- quake of a given magnitude can occur; (f) a preliminary assessment of the potential for reservoir-induced landslides; 2 - 6 development of preliminary estiamtes of ground motions at the Project sites from preliminary maximum credible earthquakes in the site region; development of a proposed 1981 study plan to improve understand- ing of the structural and seismic setting of the site region and to refine the judgments needed for seismic design; and preparation of this interim report to summarize the results of the 1980 study. Completion of the scope of the 1980 study involved approximately a 60 person-month level of effort. This included: approximately 15 person-months for the data compilation, items (a) and (b) above; 25 person-months for the field studies, items (c) and (d) above; and 20 data analysis and report preparation, items (e) h ( i) above. Fault Study Rationale 2.4.1 -Conceptual Approach The earth's crust is comprised of a series of plates that are moving relative to one another. Although the mechanism respon- sible for this movement is not completely understood, a variety of interact ions between plates can occur as a result of this move- ment. These interactions can include: collision, with resultant subduction (underthrusting) of one plate beneath another; ex- tension, where adjacent plates move away from each other; or shearing, where adjacent plates pass each other at different relative rates. Examples of these types of interactions are discussed by a number of investigators including Wilson (1963)j Dewey (1972), Cowan and Silling (1978) and Scholl and others ( 1980). 2 - 7 The type of plate interaction depends on a number of factors, such as the relative rate of movement of adjacent plates, the relative direction of these plates, and the type of crust involved ( i. e., oceanic or continental). In the case of call ision between two crustal plates (one of cant inental and the other of oceanic crust), the plate with the heavier oceanic crust typically is subducted (underthrust) beneath the continental crust. Eventually, this subducting plate falls or is thrust downward into the upper mantle and becomes detached (or dis- engaged) from the overriding plate. Where subduct ion is occurring, the subduct ion process generates tectonic stress (a) within the downgoing plate, (b) within the overriding crustal plate, and (c) along the interface between the two plates where they are in contact with one another. The stress is stored as accumulated strain energy. When the elastic limit of crustal material within or between the plates is reached, failure (fault rupture) occurs, releasing the accumulated energy along planes of weakness (faults) in an earthquake. Thus, earthquakes occur as the result of rapid displacement along fault planes. The instantaneous release of energy (the earthquake) occurs in part in the form of seismic waves which are propagated through the earth 1 s crust and mantle and which result in ground motion, commonly referred to as earthquake shaking. Faults are typically subject to repeated displacements as long as the tectonic stress environment remains unchanged. Therefore, faults which show evidence of recent displacement are assumed to have the potential for future displacement. These faults are sub- ject to surface rupture when the energy released is at a suffi- ciently shallow depth that the fault rupture plane intersects the ground surface. When the energy release occurs at depth, and when the energy release is small relative to the depth of occurrence, 2 - 8 the fault rupture plane exists at depth and does not rupture the surface of the crust. Further, for displacement slippage along fault planes in the subducting plate and along small fault planes at depth in the overriding crustal plate, the fault rupture plane does not reach the ground surface. Therefore, movement along these faults does not affect consideration of surface fault rupture potential at a given location. However, movement along these faults may affect seismic design considerations. This effect can be evaluated from the historical seismicity records and from theoretical considerations. From this evaluation, the size earthquake that can be expected to occur can be estimated and the size of the fault rupture plane can be inferred. For faults in the overriding crustal plate, along which energy release is sufficiently large and shallow to rupture the ground surface, the following factors affect consideration of these faults. During geologic time, the movements between plates may change, resulting in a changed tectonic stress environment. When exposed to a new tectonic stress environment, some of these pre-existing faults may serve as planes of weakness along which slippage may continue to occur; other pre-existing faults will no longer be the location of slip, although they continue to be zones of weakness in the crust. Thus, at a given location during a specific period of geologic time, displacement along faults, resulting in earth- quakes, is controlled by the stress environment influencing that part of the crust at that time. The type of displacement that can occur along a fault is a func- tion of the orientation of the prevailing stress regime relative to the orientation of the faults and the plane in which strain release can be most readily accommodated. Figure 2-1 shows the 2 - 9 various components of displacement or slip which can occur along a fault together with applicable terminology. The three primary types of faults are thrust or reverse, normal, and strike-slip or shear faults (Figures 2-2 through 2-4). Faults with recent displacement can occur as relatively simple, individual traces along which displacement occurs (primarily strike-slip faults) or as a complex pattern of fault traces within a fault zone (primarily reverse and normal faults). Within fault zones, some traces or planes can be undergoing recent displacement while the rest of the zone is quiescent with no recent displace- ment (as shown in Figure 2-5). The frequency of the cyclic elastic strain buildup and release by fault rupture varies greatly from one part of the earth's crust to another. The interval between earthquakes on the same fault or fault system is potentially long. However, the available world- wide historical records, which may encompass several hundred years of surface rupture and earthquakes, typically do not cover a long enough period to forecast reliably the location or frequency of future surface rupture and associated earthquakes. Often, the most informative record of historical surface rupture and associated earthquakes is best preserved in surficial materials cut by the faults. If the stratigraphic record is complete and observable and if the ages of surficial materials, especially of the Quaternary period, are known, then the most recent geologic information on past tectonic stress environments and past earth- quake activity can be deduced. Therefore, the most reliable approach to evaluating potential surface rupture and earthquake potential is one that relies substantially on understanding the geologic record of the past tens of thousands to millions of years. 2 -10 Surface rupture and the related earthquake potential at a given location in the earth's crust or lithosphere can be evaluated by u s i n g t h e c o n c e p t o f f a u lt s w i t h r e c en t d i s p l a c em e n t . T h i s concept, as it is most commonly applied, relies on the history of the surface fault rupture (or displacement); if displacement has occurred on a fault within a specified time, the fault is classified as having recent displacement. Faults with recent displacement (as defined for a particular project), are then inferred to have a potential for surface rupture and earthquakes. This potential is then considered in the design of that project. Guidelines defining what is considered "recent displacement" for this project are described in Section 3.1.2. A fault which has been subject to frequently occurring and large recent displacement appreciably affects the surface geology and topography. In such an area, it is improbable that all evidence of young faulting would be completely obliterated by weathering, erosion, and deposition. A fault that has been subject to rela- tively infrequent and small displacement may not greatly affect the landscape, and the evidence of geologically young faulting may be difficult to detect and to evaluate. However, experience during the past decade or so has indicated that the exceptional case is the one for which no evidence of fault activity can be found, provided detailed studies are completed by geologists experienced in assessment of fault activity (Sherard and others, 1974). Incomplete preservation of diagnostic geomorphic features and of stratigraphic evidence along a given length of fault requires that investigations designed for identifying and evaluating faults with recent displacement be regional in scope. Individual faults should be traced for considerable distances in order to evr?lluate adequately the tectonic setting and the amount, style, age, and frequency of past displacements. 2 -11 Incomplete evidence for conclusive evaluation of fault activity along short portions of faults is a common problem in Alaska. Critical stratigraphic evidence may often be destroyed or buried where a fault trends along or crosses a river valley; this is because of intense erosion or rapid deposition that can occur near rivers or in a fluvial basin. Another common problem in Alaska is that geomorphic evidence of faulting may be covered or masked by glacial or periglacial processes. In addition, the surficial materials deposited in river valleys, such as in the Susitna River valley, often are not old enough to be evaluated effectively for recent fault displacement. Sometimes adequate evaluation of recent fault displacement can only be made with confidence at locations remote from Project sites; in these areas, which are away from the area of active erosion and deposition, the stratigraphic and geomorphic evidence necessary for a confident assessment of fault activity is pre- served. When no conclusive evidence of recent displacement is observed along faults in the vicinity of the sites, it is reasonable to apply (to these faults) an understanding of the characteristics of geologically similar faults that are remote from the site. In this way, the recency of displacement on faults that are present in the vicinity of Project sites can be evaluated. The degree of confidence in such evaluations depends upon the quality, quantity, and strength of the evidence; this evidence may vary from fault to fault and from location to loca- tion. Procedures generally used for the regional evaluation of recent fault displacement include a multidisciplinary review of litera- ture, interpretation of regional remotely sensed data (i.e., U-2 near-infrared color photography, satellite imagery, and geophys- ical data), and review of historical seismicity data. Features 2 -12 that are potentially of interest to the Project are then re- viewed.in detail on the aerial photographs. Surface faults that have had displacement in recent geologic time are expressed in youthful units by characteristic geomorphic fea- tures such as scarps, 1 i near vegetation a 1 patterns, groundwater barriers, and lithologic contrasts. These features which are visible on aerial photographs, are usually expressed in linear or semilinear configurations (referred to as lineaments), and are visible during aerial reconnaissance. However, 1 ineaments are also produced by other erosional, depositional, structural, or cultural processes. After preliminary results are obtained from the above procedures, additional investigations can be conducted for selected features as appropriate. These investigations can include reconnaissance and/or detailed field mapping, aerial reconnaissance, Quaternary geology studies, age-dating of selected units, trenching, dril- ling, or the installation of microearthquake networks. The interpretation of the results of these investigative proce- dures forms the basis for: delineating faults with recent dis- placement; estimating the amount and type of displacement; and estimating the size of the maximum credible earthquake that might be expected during displacement along an individual fault. There are major constraints limiting the observation of faults with recent displacement in the Talkeetna Mountains. These constraints include: (a) youthful geologic processes, primarily glaciation; (b) a lack of information on the glacial deposits in the Talkeetna Mountains; and (c) the lack of detailed bedrock and surficial mapping within the Talkeetna Mountains. 2 -13 The youthful geologic processes involve primarily recent wide- spread glacial events that tend to obliterate or remove older Pleistocene units, soil horizons, and morphologic features. The result is widespread youthful deposits and surfaces that provide information on fault activity only in the most recent geologic time (i. e., the last 10,000 years). The absence of detailed glacial and bedrock data in the Talkeetna Mountains makes the evaluation of faults and faults with recent displacement difficult, because the information necessary to understand the faults is lacking. 2.4.2 -Surface Rupture and Earthquake Magnitudes Several authors have investigated the relationship between earth- quake size and length of fault rupture (Tocher, 1958; Bonilla and Buchanan, 1970; Patwardhan and others, 1975; Slemmons, 1977). On the basis of their work, it appears that surface rupture is typically associated with shallow earthquakes of magnitude (Ms) 5.5 or greater, although earthquakes of smaller magnitude have been associated with surface rupture (e. g., the Imperial, Cali- fornia, (Ms) 3.6 earthquake of March, 1966, which was associated with 0.6 inches (1.5 em) of displacement (Slemmons, 1977). On the basis of the available data, and to be reasonably conservative, a magnitude of (Msl 5 was selected as the lower magnitude value for earthquakes having the potential for associated surface rup- ture. Albee and Smith (1966) have plotted length of observed surface faulting (or long axis of aftershock area) versus magnitude. Their best fit curve suggests that at least a 5-mile (8-km) long rupture length would be necessary for an earthquake greater than magnitude (Ms) 5 to occur. However, events of higher magnitude are shown to have occurred on faults with as 1 ittle as 0.6 miles 2 -14 (1 km) of rupture length. Slemmons (1977) in his evaluation of earthquakes, faults, surface rupture, and displacement shows 3 miles (5 km) as generally being the shortest rupture length on which events of magntiude (Ms) 5 or larger have occurred (although one event, the 1951 Superstition Hillss California, event of magnitude (Ms) 5.6 had 2 miles (3 km) of surface rupture length). Considering the Slemmons {1977) and Albee and Smith (1966) data, we assume that approximately a 3-mile (5-km) long surface rupture length is necessary to generate a magnitude (Ms) 5 or larger earthquake. For the purposes of this study, it is assumed that the observed length of a lineament or fault represents half the potential 1 ength of a. fault and the observed 1 ength represents the maximum probable rupture length should the fault have recent displacement (the rationale for this concept is presented in Section 3.2). The observed 1 ineament or fault length. ( i. e .• the potential rupture length) has been used to evaluate seismic source potential and to infer the maximum amount of displacement that could occur during a single earthquake. This approach introduces a relatively large degree of conservatism to the study. Typically, the maximum potential rupture length of a fault during a single event is assumed to be one-half of the observed fault length (as discussed in Wentworth and others (1969)). 2.5 -Method of Study The methodology employed for the seismic geology study is summarized in Figure 2-6 and is described below. Information of a geologic (including geomorphic) and seismologic nature was evaluated to identify previously reported faults and 1 i neaments that may be fau lt-re 1 ated in the area within 62 miles (100 km) of the Project (Figure 1-1). The methodol- ogy associated with both the geological and seismological portions of the investigation are described below. 2 -15 The geological portion of the investigation included: a comprehensive review of the literature (approximately 350 references were reviewed); discussions with other geologists familiar with the study area; inter- pretation of selected remotely sensed data (approximately 250 images and aerial photographs were reviewed); aerial reconnaissance; and limited field studies of the identified lineaments and faults that are within 62 miles (100 km) of the Project. The locations of lineaments, faults 1 and inferred faults derived from the literature review and from discus- sions with other geologists were plotted on a 1:250,000-scale topo- graphic base for the study area. Lineaments considered to be possibly fault-related were interpreted on high-altitude color-near-infrared photographs (scale 1:125,000) and on LANDSAT imagery (scale 1:1,000,000 and 1:500,000). The coverage of imagery and photography used for this study is shown in Appendix A. These data were plotted on the photograph or image on which they were observed. For the identification of potential seismic sources, length-distance screening criteria were developed to select only those faults and linea- ments for further evaluation which potentially could be of concern for seismic design. These criteria were based on available worldwide data on faults with recent displacement, associated maximum magnitude earth- quakes, and an attenuation relationship applicable to the western United States (the latter is discussed in Section 12). The length-distance screening criteria and the rationale behind their development are discussed in detail in Section 3.2. Features which were long enough and close enough to the site to meet the length-distance screening criteria were plotted on 1:250,000 scale field maps. In addition, to evaluate potential surface rupture in the vicinity or through the sites, all faults and lineaments that passed within 6 miles (10 km) of either site were plotted on a 1:63,360 scale topographic base map and on U-2 color near-infrared photographs at a scale of 1:125,000. These features were then evaluated during the field reconnaissance. 2 -16 the field reconnaissance, each fault~ and 1 ineament was examined for character.istics indicative of faulting and recent displacement. The field reconnaissance involved helicopter and fixed-wing aerial recon- naissance of all faults and lineaments within the site region which were sidered to be potentially significant to the sites. The aerial reconnaissance included systematic review of all quadrangles within the site region to locate faults or lineaments which were not identified Ground reconnaissance studies were conducted at selected ocations along specific lineaments to augment observations made during Observations were documented in writing and n photographs as described in Appendix A. The purpose of this part of investigation was to ascertain, on a reconnaissance level, which ures in the site region are, or potentially are faults with recent isplacement. This field effort was conducted from 1 July 1980 through 21 August 1980. The faults and lineaments were classified during the reconnaissance: as having been subject to recent displacement; as being indeterminate features with a moderate, low to moderate, or low likelihood of recent displacement; or as being nonsignificant, i. e .• learly not a fault. Section 8.2 describes the basis on which the classifications were made. seismological input into the lineament and fault evaluation pro- cess included a review of available historical and recent earthquake activity and a review of unpublished data obtained from the National Oceanic and Atmospheric Administration (NOAA), the Geophysical Institute at the University of Alaska, and the U. S. Geological Survey. The data were reviewed to assess accuracy and completeness before computer processing and cataloguing. From these data, a catalog was compiled of historical earthquake and microearthquake data which includes all available records. Computer plots of epicenters, at a scale of 1:250,000, were used as overlays to geologic maps and were compared \vith the 1:250,000-scale compilation of faults and lineaments. The computer plots were checked for clusters or alignments of epicenters that would 2 -17 suggest the presence of a fault. Seismologic data were further analyzed to estimate maximum earthquake magnitudes for seismic clusters and alignments and for recurrence intervals of earthquakes of varying magnitudes. Available earthquake data were also reviewed to assess both the adequacy of the data and the effect of this factor on the seismologic analyses. A 10-station microearthquake network was installed within a 30-mile (48-km) radius about each proposed site. The network was in opera- tion for three months, from 28 June 1980 through 28 September 1980. Seismograms of earthquakes recorded by the network were used to calcu- late the size (magnitude). location (epicenter), focal depth, and focal plane mechanism of the earthquakes. Preliminary analysis of events recorded by the network were made in the field using a portable minicomputer. These preliminary analyses were compiled concurrently with the fault and lineament field studies. This multi-disciplinary approach permitted field evaluation of areas with apparent concentrations of seismic activity to assess whether or not correlations should be made. Subsequent to completion of the field studies, the geologic and seismo- logic data were reviewed and checked for accuracy. The faults and lineaments which were judged to have a potential effect on consideration of seismic design and surface rupture through the sites were selected by use of the criteria described in Section 8.3, The preliminary evalua- tion of reservoir-induced seismicity was completed using procedures described in Section 10. The results of the data compilation, field studies, and data analyses were then compiled and are presented in this report. 2 -18 FAULT STRIKES N30°E (COMPASS DIRECTION) ORIZONTAL COMPONENT OF IP-SLIP COMPONENT VERTICAL COMPONENT OF DIP-SLIP COMPONENT AND VERTICAL-SLIP COMPONENT HORIZONTAL PROJECTION OF S Ll P VECTOR P-SLI P COMPONENT Block diagram illustrating the various components of fault slip. The fault illustrated here is an oblique-slip fault with a left-slip component combined with a normal-slip component. The dip and strike together comprise the attitude of the fault. The slip vector, a line, lies in the fault surface and has a true length that can be designated in terms of a vertical component and a horizontal component. It can also be depicted in terms of its horizontal projection and its angle of plunge. BLOCK DIAGRAM OF VARIOUS FAUlT SLIP COMPONENTS DE CONSULTANTS 14658A December 1990 FIGURE 2-1 Block diagrams showing schematic effects of shift along a reverse-slip fault: (A) before the most recent shift, (B) after the most recent shift. A B BLOCK DIAGRAMS Of SCHEMATIC EFFECTS OF SHIFT ALONG A REVERSE-SUP FAULT D·CLYDE CONSULTANTS 14658A December 1980 FIGURE 2-2 Block diagrams showing schematic effects of shift along a normal-slip fault: (A) before the most recent shift, (B) after the most recent shift. A B BlOCK DIAGRAMS OF SCHEMATIC EFFECTS OF SHIFT AlONG A NORMAl-5UP FAUlT E CONSULTANTS 14658A December 1980 FIGURE 2-3 Block diagrams showing schematic effects of shift along a strike-slip fault: (A) before the most recent shift, (B) after the most recent shift. D-CLYDE CONSULTANTS 14658A December 1980 BLOCK DIAGRAMS OF SCHEMATIC EFFECTS Of SHIFT ALONG A STRIKE-sUP FAULT FIGURE 2-4 F Block diagram illustrating the relationship of a fault zone with recent displacement to a fault zone. This example is a left slip fault. Although the fault zone is composed of several fault planes or traces, the geomorphic features within the fault zone indicate that the most recent surface faulting has occurred along the planes labeled as fault trace with recent displacement. On the basis of geomor- phic evidence, the location of potential future surface faulting within this fault zone is judged to be along the planar features labeled as fault trace with recent displacement. The width of the area that potentially could be affected by future surface faulting, is judged to be that of the fault zone with recent displacement. BLOCK DIAGRAM OF RELATIONSHIP Of A fAULT ZONE WITH RECENT DISPLACEMENT TO A FAULT ZONE DE CONSULTANTS 14S5SA DacBmbor 1000 FIGURE 2-5 REMOTE SENSING INTERPRETATION NO MICROEARTHQUAKE NETWORK NO NO ADDITIONAL STUDY CANDIDATE FEATURE NO ADDITIONAL STUDY OF CANDIDATE FEATURE NO NO ADDITIONAL STUDY OF CANDIDATE SIGNIFICANT FEATURE ALL FAULTS & LINEAMENTS IDENTI FlED IN SITE REGION CANDIDATE FEATURE SEISMIC AND GEOLOGIC FIELD INVESTIGATIONS YES OR INDETERMINATE ESTIMATE PRELIMINARY MAXIMUM CREDIBLE EARTHQUAKES ESTIMATE POTENTIAL FOR SURFACE RUPTURE IN VICINITY OF DAMS CANDIDATE SIGNIFICANT FEATURE DEVELOP PROPOSED 1981 STUDY PLAN 0-CLYDE CONSULTANTS 14658A December 1980 LITERATURE REVIEW AERIAL AND GROUND RECONNAISSANCE 1980 SEISMIC GEOLOGY FLOW DIAGRAM FIGURE 2-6 0-FAULT EVALUATION CRITERIA AND GUIDELINES al sets of criteria and guidelines are typically developed and used the course of a seismic geology investigation. They provide a method of identifying faults and lineaments which are impor- t to design considerations. For this investigation, four sets of iteria and guidelines have been developed. These sets are: Guidelines to clarify, for purposes of the Project, the definition of a fault with recent displacement. Length-distance screening criteria. These were developed prior to the field reconnaissance studies to identify only those faults and lineaments that could potentially be significant to consideration of seismic source potential and/or potential surface rupture through the dam sites. Preliminary significance criteria. incorporating the results of the field reconnaissance studies. These identify candidate significant features that could potentially be significant to consideration of seismic source potential and/or potential surface rupture through the sites. These criteria represent a refinement of the screening process conducted in (2) above. The refinement is based on the observations made during the field reconnaissance studies and takes into account initial judgments regarding ground motions and pre- . liminary maximum credible earthquakes. Significance criteria~ which are refinements of the preliminary significance criteria. These identify significant features which are of potential importance to consideration of seismic source potential and/or potential surface rupture through the sites. These significant features are to be further evaluated and studied during the field studies planned for 1981. 3 - 1 Recent fault displacement and length-distance screening criteria are discussed below in Sections 3.1.1 and 3.1.2, respectively. The prelimi- nary significance, and significance criteria are discussed in Section 8.3 as an introduction to the discussion of the significant features. 3.1 -Guidelines for Defining Recent Fault Displacement Criteria 3.1.1 -Regulatory Criteria The criteria described in this section are those regulatory guide- lines which have been used for other projects of similar magnitude to this Project. The agencies for which criteria were reviewed include: the Water and Power Resources Service, formerly called the U.S. Bureau of Reclamation (USBR); the U.S. Army Corps of Engineers; the Nuclear Regulatory Commission; the Federal Energy Regulatory Commission ( FERC); the State of Alaska; and the State of California. Agencies responsible for critical structures such as dams and power plants have developed criteria which are used to evaluate the importance of faults to these structures. These criteria typically deal with one aspect of faulting, the recency of movement or dis- placement along a fault. Faults which have had displacement within a specified time period have been assigned descriptive terms such as active fault or capable fault. The review below provides a summary of regulatory criteria used previously on other projects (including dams and power plants) to define active faults, or capable faults. These criteria have been considered in defining, for the Project, the term fault with recent displacement. 3 - 2 Water and Power Resources Service (WPRS) Criteria for defining an active fault were adopted by the WPRS (formerly the USBR) for evaluation of faults at the proposed Auburn Dam site in California (Cluff, Packer, and Moorhouse, 1977). An active fault was defined as a fault which had been subject to relative displacement during the last 100,000 years. A fault is considered active if it (a) exhibits direct evidence of displacement in deposits less than 100,000 years old (e. g., surface rupture); (b) has indirect evidence of displacement on the fault, on or in deposits less than 100,000 years old (e. g., offset streams, scarps, etc.); or (c) has earthquake epicenters which have been accurately defined instrumentally or well-docu- mented historically and which produce a geometrical arrangement that demonstrates a direct relationship to the fault. An inactive fault is one for which there is direct evidence that there has not been relative displacement during the past 100,000 years. U. S. Army Corps of Engineers (USACE) The U. S. Army Corps of Engineers defines a capable fault as one which has had: (a) displacement in the past 35,000 years; (b) a demonstrated relationship with macroseismicity (magnitude greater than or equal to 3.5) based on instrumental data; or (c) a structural relationship with a known active fault where movement on one would cause movement on the other (U. S. Army Corps of Engineers, 1977). U. S. Nuclear Regulatory Commission (USNRC) The U.S. Nuclear Regulatory Commission (formerly the U.S. Atomic Energy Commission), defined a capable fault as one which exhibits one or more of the following characteristics: 3 - 3 (1) Movement at or near the ground surface at least once within the past 35,000 years, or movement of a recurring nature within the past 500,000 years. (2) Instrumentally determined macroseismicity with records of sufficient precision to demonstrate a direct relationship with the fault. (3) A structural relationship to a capable fault according to characteristics (1) and (2) above such that movement on one could be reasonably expected to be accompanied by movement on the other (U. S. Nuclear Regulatory Commission, 1975). Federal Energy Regulatory Commission (FERC) Federal Energy Regulatory Commission regulations and guidelines, as they apply to dam projects, do not discuss or define faults (Federal Energy Regulatory Commission, undated; Acres American Inc., 1980). State of Alas State of Alaska regulations and guidelines, as they apply to dam projects, do not discuss or define faults or faults with recent displacement. The only reference encountered to date which per- tains to faults is contained in Standards of the Alaska Coastal Management Program. Included under the subject of 11 geophysical hazards 11 is the term 11 severe faults.11 No definition of this term is provided. State of California Division of Mines and Geology (CDMG) The Alquist-Priolo Special Studies Zone Act of 1976 defines a 11 sufficiently active 11 fault as one along which the most recent 3 - 4 k': ;;,,~~"~~--~ ' movement along one or more of its segments or branches can be dated, by evidence or inference, within Holocene time (the last 11,000 years) (Californa Division of Mines and Geology, 1976). Evidence for activity on a fault in historic time (the last 700 years) can include one or more of the following: (a) observed fault rupture or creep; (b) evidence of seismicity clearly associated with the fault; and (c) strain measurable across the fault. These regulatory definitions of a fault with recent displacement, while useful, can lead to a somewhat simplistic and possibly misleading concept of the significance of a particular fault. If a fault has been subject to displacement within a specified period of time, whether it is 11,000 years, 35,000 years, or 100,000 years, it is import ant to understand how much displacement has occurred, how often it has occurred, and the sense of displacement. For ex am p 1 e , a f a u lt t h at h a s b e e n s u b j e c t t o 0 . 2 i n c h e s ( 5 mm ) of displacement every 75,000 years and a fault that has been displaced 3.3 feet (1m) every 10,000 years both can be considered to have recent displacement (if displacement within 100,000 years is used as the definition of a fault with recent displacement). But for purposes of dam design, the effect of displacement on these two faults can be significantly different. In addition, the sense of relative displacement is also important. As discussed by Sherard and others (1974), the effect on dam design of displacements on thrust faults, normal faults, and strike-slip faults is different for each type of fault. Dams have been designed to accommodate ground motions from rela- tively large earthquakes which have occurred relatively close to the dam. For example, the San Pablo Dam in California is designed to accommodate the ground motions of a magnitude (Ms) 8-1/2 event 3 - 5 on the San Andreas fault and a magnitude (Ms) 7-1/2 event on the Hayward fault, approximately 12 miles (20 km) and 10 miles (16 km) from the dam, respectively. Dams have also been designed to accom- modate surface rupture. For example, the Coyote Springs Dam, built in California in 1936, was designed as an earth dam to accommodate 20 feet (6 meters) of horizontal displacement and 3.3 feet (1 meter) of vertical displacement in the foundation. No displacement along the fault has been reported, and the dam continues in service without problems. Consequently, any consideration of faults with recent displacem~nt ultimately needs to address not only how recently the fault has had displacement, but also how much displacement has occurred, how often it has occurred, and what the sense of displacement has been. From these data, an assessment can be made of the likelihood that the fault will have these characteristics in the future. From this assessment, the seismic source potential and potential for surface rupture for a particular fault can be considered in an appropriate fashion during dam design. 3.1.2 -Guidelines for Identifying and Studying Faults with Recent Displacement The guidelines presented below are based on the current state-of- the-knowledge for identifying faults with recent displacement. As developments and improvements evolve, they should be incorpo- rated into future studies and into these guidelines. It is recog- nized that data allowing straight-forward determination of the recency of displacement along a fault are often lacking and that the judgment of the investigator is required in the final determi- nation. These guidelines have been prepared by Acres American Inc~ after review of regulatory and dam building agency guidelines (dis- cussed in Section 3.1.1) and after discussions with project team members. 3 - 6 (1) All lineaments or faults that have been defined by the geology and seismology community as having been subject to recent displacement should be included in assessing the seismic design criteria for the Project. (2) If a 1 ineament exists within 6 miles (10 km) of a structure site, or if a branch of a more distant lineament is suspected of passing through a structure site, then a more detailed investigation should be made to establish whether the feature is a fault, whether or not it can be considered to have recent displacement, and ~'lhether the potential for displacement in the structure foundation exists (structures, as used here, refers to dam structures). (3) Investigation of features identified in Item 2 should deter- mine whether these features have experienced displacement in the last approximately 100,000 years. (4) Lineaments more distant than 6 miles (10 km) from a structure site, and for which deterministic impact on the site may con- trol the design of a structure, should be investigated to determine if the lineament is a fault and if it has moved within the last approximately 100,000 years. (5) All features identified as faults which have experienced movement in the last approximately 100,000 years should be considered to have had recent displacement. All faults with recent displacement warrant consideration when assigning design criteria for ground motions or for surface displacement at the structu~e sites. 3 - 7 3.2 -Length-Distance Screening Criteria Review of regulatory criteria combined with the state-of-the-knowledge for faults, earthquakes, and surface rupture (discussed in Sect ion 2.4.2) led to the development of length-distance screening criteria to identify potentially significant faults and lineaments (called candidate featues in this study). These screening criteria were applied to all faults and lineaments identified in the literature and on remotely sensed data as discussed in Section 2.5. The screening criteria were developed to identify candidate features on,the basis of (a) seismic source potential and (b) potential for surface rupture through the dam. Potential Seismic Sources Screening criteria for potential seismic sources were developed using (a) empirical length of rupture and earthquake magnitude relationships and (b) distance of the fault or lineament from either site. Length of rupture and earthquake magnitude relationships typically have been considered in two ways. One method is to measure surface rupture length which occurs on faults during earthquakes. Slemmons (1977) has presented the most recent published compilation of rupture lengths on different types of faults during earthquakes of various magnitudes. A second method is to define the rupture length as the length of the aftershock zone associated with earthquakes. Cluff, Tocher, and Patwardhan (1977) have summarized this approach and have developed a numerical relationship between the two parameters. Figure 3-1 shows the rel at ionsh ip between earthquake magnitudes and the length of the aftershock zone associated with earthquakes of specific magnitudes. The length of the aftershock zone is generally greater than the length of ground rupture during an earthquake, because the aftershocks represent continual strain release after the 3 - 8 shock and may migrate laterally along the fault plane. There- to the values derived from Figure 3-1 as surface rupture lengths, one of several degrees of conservatism is added to the criteria developed for assessing faults and lineaments for this study. The data derived from Figure 3-1 are presented in Table 3-1 as between fault rupture length and earthquake of the surface trace of the fault or lineament from either site is considered along with the postulated maximum fault rupture length (a) to screen out potential seismic sources for which associated ground motions would be too small to be significant to the project and (b) to retain those that are of potential significance. These length-distance criteria accommodate the fact that at greater distances from the sites only the longer faults and l ine~ments have the potential to generate ground motions of potential signif- icance to the site. The length-distance criteria presented in Table 3-2 were used for this study. They were derived from the rupture lengths presented in Table 3-1. The criteria use the observed length of the fault or lineament as the maximum length that could rupture during a given earthquake. This is a conservative approach because fault rupture length is typically assumed to be half the observed fault length (Wentworth and others, 1969). The values given in Table 3-2 include a degree of conservatism in that the maximum hypothetical earthquake is assumed to occur at the closest approach of the observed portion of the fault or lineament to either dam site. The length-distance criteria set up concentric zones around the sites in which faults or lineaments of a set minimum length would be further evaluated. Thus, at distances of less than 6 miles (10 km) from either dam, all faults or lineaments with a length of 3 miles (5 km) 3 - 9 or more were selected for further evaluation during the field recon- naissance. These represent potential faults that may generate a mag- nitude 5 or greater earthquake. At distances of 6 to 31 miles (10 to 50 km) from either dam, all faults or lineaments that are at least 6 miles (10 km) long were further assessed. Faults and lineaments with a minimum length of 31 miles (50 km) at a distance of 31 to 93 miles (50 to 150 km) from either dam were also examined during the field reconnaissance. These length-distance criteria represent the experience from worldwi~e case histories of earthquakes and their associated rupture lengths along faults. They are also in accordance with previous regulatory guidelines. This approach was used to select faults and lineaments, from those which had earlier been identified from the literature and interpreta- tion of remotely sensed data, for additional assessment during the field reconnaissance; they were chosen because of their seismic source potential. In addition to features meeting the above criteria, screening was conducted to select features with a potential for sur- face rupture through either site, as discussed below. Potential for Surface Rupture Through the Dam A screening criterion for potential surface rupture was developed from experience with faults with recent displacement. The criterion incorporates variations in the type and extent of displacement associated with different types of faults. Faults with historic rupture vary greatly in the pattern of rupture that has occurred. Some faults have single, relatively narrow surface traces, while others have branching patterns that include displacement on secondary or splay faults at some distance from the main fault, as shown by Ambrasseys (1968) and Bonilla (1970). 3 -10 The width of the zone of rupture is related to a large extent to the type of fault and the type of displacement along a fault. As dis- cussed by Sherard and others (1974) and Bonilla (1970), displacement on branch and subsidiary faults occurs more commonly on normal and thrust (reverse) faults than on strike-slip faults. Figure 3-2 shows this relationship where the maximum width of the zone within which displacement has occurred on strike-slip faults is 10 feet (3m) to 1.8 miles (3 km). The maximum width for normal and thrust (reverse) faults varies from less than 0.1 to 8.5 miles (0.06 to 13 km). A corollary to this is the observation that the zone of deformation in thrust (reverse) faults typically is in the upthrown side, whereas for normal faults the displacement typically is in the downthrown side (Sherard and others, 1974). Using these empirical relationships for width of zone along which displacement occurs during a single event, a screening criterion for features with potential surface rupture through either dam has been developed. The criterion is that those faults and lineaments (iden- in the 1 iterature and on remotely sensed data) whose observed passes within 6 miles (10 km) of either site will be retained for additional assessment during the field reconnaissance study. This criterion is consistent with the degree of conservatism used for other projects of similar magnitude (e. g., criteria adopted by the Water and Power Resources Service as described in Section 3.1.1). In summary, the length-distance screening criteria, developed prior to the field reconnaissance study, were developed to select all features that potentially could be of significance to Project design either because they represent potential seismic sources or because they have the potential to cau~e surface rupture through either site. The screening criteria listed in Table 3-2 were used for the selection of potential seismic sources. For the selection of features with surface rupture potential through either site, the criterion of all faults and 3 -11 lineaments within a 6-mile (10-km) radius of either site was used. The faults and lineaments selected through application of these screening criteria have been designated candidate features and were evaluated during the field reconnaissance portion of the study. 3 -12 TABLE 3-1 MEAN RELATIONSHIP BETWEEN FAULT RUPTURE LENGTH AND EARTHQUAKE MAGNITUDE Magnitude Rupture Length (Ms) (km) (miles) 5 5 ( 3) 6 12 (7) 6.5 18 ( 11) 7 45 (28) 7.5 130 (81) Notes: 1. Data were obtained from Cluff, Tocher, and Patwardhan (1977). 2. Data are shown in Figure 3-1. TABLE 3-2 LENGTH-DISTANCE CRITERIA FOR IDENTIFICATION OF FAULTS AND LINEAMENTS FOR PRELIMINARY FIELD RECONNAISSANCE Distance from Dam Site Minimum Alignment Fault or (km) (miles) (km) 0 to 10 (0 to 6) 5 10 to 50 (6 to 31) 10 50 to 150 ( 31 to 93) 50 Length of Lineament (miles) ( 3) (6) (31) Note: The basis for selection of these criteria is described in Section 3.2 2000 1000 900 800 700 600 500 400 200 100 90. 80 70 60 50 40 30 20 10 g 8 7 6 5 4 3 2 1 I / / 7 / IT' I ~ ~ / 3 4 5 I I I !I ~ I I / ®/ J /~ • I 6 7 Mean / II ...._, fi +1a -1 a I I I I I I 11 I~ L_f, I 'i @I I I I 8 9 MAGNITUDE E CONSULT ANTS 14658A December 1980 GRAPH SHOWING THE RELATIONSHIP BETWEEN EARTHQUAKE MAGNITUDE AND THE LENGTH OF AFTERSHOCK ZONES FIGURE 3-1 0 m 0 0 z (/) c r --1 )> z --1 (/) ~ Ol U1 00 )> 0 "' ,., "' 3 C" ~ -rD CD 0 -n G) c :tl m w (IJ "'0 :J :::::: c rn Ill E (IJ ~ Ill :J cr ..c t co w 8 7 6 5 4 0.00'1 0.005 0 0.01 0.05 0.1 .6.0 0 0 0 0 k), 0 0 0 D 0 0.5 1 5 10 LEGEND Distance from centerline of fault zone to fault trace with recent displacement (miles) Main Branch Secondary 0 Strike-slip faults D ~ 0 Normal faults Right-normal faults Reverse faults NOTE 1. After Bonilla (1970). SURFACE RUPTURE ZONE WIDTH RELATIONSHIPS ~~----------------------------------------------------------------------------------------------------------------~ Setting plate tectonics have been a major influence in tectonics of Alaska. Plate tectonics s the underlying cause of the geologic and seismic activity in and southern Alaska as the product of the subduction of the c Plate at the Aleutian Trench as the plate spreads northward from as'{ Pacific Rise (!sacks and others, 1968; Tobin and Sykes, 1968). orthward movement occurs at a rate of approximately 2.4 inches/yr relative to the North American Plate and is illustrated in As the Pacific Plate reaches the Aleutian Trench, it is er the portion of the North American Plate that includes Gulf of Alaska area, the interplate movement is expressed as t y 1 e s of deform at i on : r i g h t-1 ate r a 1 s 1 i p a 1 on g the Queen 6tte and Fairweather faults; underthrusting of the oceanic Pacific beneath the continental block of Alaska; and a complex transition of oblique thrust faulting near the eastern end of the Aleutian (Figure 4-1). The Trench represents the ground surface expres- ()f the initial bending of the oceanic plate as it moves downward h the North American Plate. ional earthquake activity is closely related to the plate tee- of Alaska. Figure 5-2 (presented in Section 5) shows an oblique atic view of the major geologic and tectonic features of the nal plate tectonics. The subducting plate is shown moving to northwest away from the Aleutian Trench (off the figure to the h) and dipping gently underneath the upper Susitna River region. ubducted material is located at depth from the hypocenter distri- on of instrumentally located earthquake activity. This kind of 4 - 1 subcrustal seismic zone is called a Benioff zone. In some areas, such as to the southwest of the site region along the Alaska Peninsula, the presence of subducted oceanic crust is revealed at the ground surface by andesitic volcanic rocks. The Benioff zone in the site region is characterized by earthquake activity extending to a depth of about 93 miles (150 km) (Agnew, 1980). No autochthonous andesitic volcanic rocks or volcanoes currently are known to be present at the ground surface above the Benioff·zone. Beneath the Prince William Sound area, which is on the North American Plate, the subducted plate moves nearly horizontally. The two plates appear to be closely coupled in this region and have the capacity to accumulate and release very large amounts of elastic strain energy. The most recent example of this process was the 28 March 1964 earthquake of magnitude (Ms) 8.4. The rupture zone of this earthquake, as evid- enced by aftershocks, is shown in Figures 4-2 and 5-2. The overlying North American Plate is also disrupted by compressional and tensional forces caused by the interplate deformation. Evidence for tectonic deformation is found in the Alaska Range more than 279 miles (450 km) northwest of the surface interplate boundary at the Aleutian Trench in the Gulf of Alaska. Much of this deformation is the composite expression of the plate interaction during millions of years and of the seaward migration of the subducting zone, which has periodically accreted additional crust to the continental land mass. Deformation within the upper plate is discussed in Section 5. 4.2 Regional Seismicity and Seismic Gaps The major earthquakes of Alaska have primarily occurred along the inter- plate boundary between the Pacific and North American Plates from the 4 -2 Alaskan Panhandle to Prince William Sound and then along the Kenai and Alaska Peninsulas to the Aleutian Islands as shown in Figure 4-2. Three great earthquakes were felt in September 1899 near Yakutat Bay, and the magnitudes (Ms) of these are estimated to be 8.5, 8.4, and 8.1 (Thatcher and Plafker, 1977). Ground deformation was extensive and ver- tical offsets ranged up to 47 feet (14.3m) (Tarr and Martin, 1912); these are among the largest known displacements attributable to earth- quakes. Large parts of the plate boundary were ruptured by these three earthquakes and by twelve others that occurred between 1897 and 1907; these included a magnitude (Ms) 8.1 event on 1 October 1900 southwest of Kodiak Island (Tarr & Martin, 1912; McCann and others, 1980) and a nearby magnitude (Ms) 8.3 earthquake on 2 June, 1903, near 5r north latitude, 156owest longitude (Richter, 1958). A similar series of major earthquakes occurred along the plate boundary between 1938 and 1964. Among these earthquakes were the 1958 Lituya Bay earthquake (magnitude (Mw) 7.7) and the 1972 Sitka earthquake (magnitude (Ms) 7.6), both of which occurred along the Fairweather fault system in southeast Alaska; and the devastating 1964 Prince William Sound earthquake (magnitude (Ms) 8.4) which ruptured the plate boundary over a wide area from Cordova to southwest of Kodiak Island, with up to 39 feet (12m) of displacement (Hastie and Savage, 1970). Figure 4-2 shows the aftershock zones of these and other major earthquakes in southern Alaska and the Aleutian Islands. The main earthquakes and aftershocks are inferred to have ruptured the plate boundary in the encircled areas. Three zones along the plate boundary which have not ruptured in the last 80 years have been identified as 11 Seismic gaps" (Sykes, 1971). These zones are located near Cape Yakataga in the vicinity of the Shumagin Island, and near the western tip of the Aleutian Chain as shown in Figure 4-2. The Yakataga seismic gap is of particular interest to the Project because of its proximity to the site region. The rupture zone 4 - 3 of a major earthquake filling this gap has the potential to extend down the Benioff zone to the north and northwest of the coastal port ion of the gap near Yakataga Bay. The area of the Yakataga seismic gap was probably ruptured extensively in the two great earthquakes of 1899 (Sykes and others~ in press). The Yakataga seismic gap extends for approximately 108 miles (175 km) between the rupture zones of the 1964 earthquake and the most recent large event on 28 February 1979 near Icy Bay (magnitude (Ms) · 7.2). Using early Russian felt reports and writings, Sykes and others (in press) show that almost all of the plate boundary along the Alaska- Aleutian Arc has been ruptured previously in large or great earthquakes. Consequently, the presently existing seismic gaps are considered to be the probable sites of future large events rather than normally quiescent areas where plate motion is relieved by aseismic slip. In Alaska, the cylcle of large earthquakes with intervening periods of relative quiescence is characteristic of activity on the Aleutian Trench along the boundary between the North American and Pacific Plates. The last large earthquakes in the Yakataga area occurred in 1899. No information is available for earthquakes before 1899 for the Yakataga area to estimate a recurrence interval, but the amount of displacement during the 1899 events amounted to about 16 feet (5m). Sykes and others (in press) estimate that 16 feet (5 m) ~ 8 feet (2.5 m) of potential displacement could have been built up as strain by the continuing plate motion (2.4 inches/yr (6 cm/yr)) since 1899, if there has been no aseismic slip. Because the 1979 magnitude (Ms) 7.2 earthquake near Icy Bay occurred in the inferred rupture zone of the 1899 ·events, a large or great earthquake may occur within the next two to three decades in the remaining portion of the Yakataga seismic gap (Perez and Jacob, in press). 4 - 4 -Historical Seismicity historical seismicity within 200 miles (322 km) of the Project is iated with three general source areas: the crustal seismic zone the North American Plate; the deep (subcrustal) Benioff zone; and allow Benioff zone. The seismicity of these three source areas is in this section following the discussion of seismic networks ir effect on detection levels and location accuracy. to the installation of a seismograph at College, Alaska (COL) in only local felt reports or seismograph recordings made at distant ons were available to determine epicenters and focal depths of hquakes in south-central Alaska. Among these distant stations were: at Sitka, Alaska, installed in April 1904, consisting of two h;..Qmori horizontal seismometers; one each at Berkeley and at Lick ervatory in California, installed in 1887 (published readings began 910 and 1911. respectively); and some Japanese stations developed in Davis and Echols (1962), Davis (1964), and Meyers (1976) have ished lists of felt earthquakes for Alaska dating from the 18th ry, although the very low-population density in Alaska prior to 0 has precluded historical felt reports of earthquakes in the ior of Alaska earlier than the large event of 1904. ihg the early and middle portion of the twentieth century, prior to • epicenters and focal depths of earthquakes in Alaska were computed imarily from teleseismic data. Location uncertainty varied greatly depended on the specific combination of earthquake size and source n depth. For example. larger earthquakes (magnitude (Ms) greater 6) occurring within the shallow Benioff zone may have been well- ed worldwide but may not have had clear pP phases to constrain and may have been located using travel time curves that did not unt for local tectonic structure. Uncertainties in location and h could be as large as 62 miles (100 km) or more. Earthquakes of 4 - 5 uncertain focal depth are often constrained to 20 miles (33 km) to compute the epicenter location. In addition, recomputations of some earlier earthquakes, such as those published by Sykes (1971), have probably reduced some of the original catalog errors. The accuracy of epicenter locations improved slightly with the installa- tion of the seismograph at College, Alaska (near Fairbanks) in 1935, but it was not until the mid 1960s, after the dev as tat ing 28 March 1964, Prince William Sound earthquake, that earthquake monitoring was sig- nificantly improved in central and southern· Alaska. After the 1964 earthquake, epicentral and focal depth accuracy improved with the installation of the University of Alaska Geophysical Institute (UAGI), National Oceanographic and Atmospheric Administration (NOAA), and U. S. Geological Survey seismic networks during the period 1964 to 1967, and with the preparation of a velocity model for the area by Biswas (1974). Since 1974, the focal depths of earthquakes recorded and located by the UAGI are accurate to approximately plus or minus 9 miles (15 km) ~vith epicentral accuracy generally better than depth accuracy. Location accuracy and magnitude detection levels have varied due to the number of stations in operation at a given time and changes in data handling procedures and priort ies, so the above values may be too small for some poorly recorded events. From 1967 to 1974, the focal depth error estimates are approximately plus or minus 12 to 19 miles (20 to 30 km), with epicentral uncertainty of plus or minus 12 to 16 miles (20 to 25 km). The accuracy of focal depth estimation within the U. S. Geological Survey seismograph network is very good, probably plus or minus 6 miles (10 km) or less. However, this network is south of the Project and generally ouside of the site region. The following discussion of historical seismicity is based on the Hypocenter Data File prepared by NOAA (National Oceanic and Atmospheric 4 - 6 inistration, 1980). Data from the U.S. Geological Survey and stations are routinely reported to NOAA for inclusion in world-wide a analysis. Thus, particularly for earthquakes of magnitude 4 and , the NOAA catalog represents a fairly uniform data set in terms quality and completeness since about 1964 (as explained below). akes larger than magnitude 4 (using any magnitude scale) or ified Mercalli Intensity V are plotted in Figures 4-4, 4-5, and 4-6. akes smaller than magnitude 4 or with no determined magnitude are included because they are considered to be too small to effect smic design considerations. 4.3.1 -Shallow Benioff Zone The shallow Benioff zone is a major source of earthquake activity that could potentially affect seismic design considerations. This zone is the region of primary interplate stress accumulation and release between the Pacific and North America Plates and is indicated in Figures 4-4 and 5-2. The 28 March 1964 Prince William Sound earthquake, discussed in Sections 4.1 and 4.2, is the closest major interplate earthquake to the site region (as shown on Figures 4-2 and 4-4). Focal depths of earthquakes within the area of the 1964 aftershock zone are generally shallow, in the range of 15 to 28 miles (25 to 45 km) as shown in Figures 4-5 and 4-6. Several additional large earthquakes have occurred during the twen- tieth century in the same vicinity as the 1964 event. Two of these, the magnitude (Ms) 7-1/4 earthquake of 31 January 1912 and the magnitude (Ms) 6-1/4 earthquake of 14 September 1932, were given focal depths of 50 and 31 miles (80 and 50 km), respectively. 4 - 7 It is 1 ikely that these depths are not correct, since the recent and better-1 ocated events are shall ower and more consistent with the tectonic model. Similar uncertainties in focal depth for earlier earthquakes are discussed in Sections 4.3.2 and 4.3.3. 4.3.2 -Deeper Benioff Zone The historical seismicity catalog as plotted in Figure 4-4 was sorted during this study to select those earthquakes with depth greater than or equal to 22 miles (35 km). This depth was selected to exclude those events constrained to a depth of 20 miles (33 km). On the basis of the results of the microearthquake study (Section 9), the seismically active portion of the upper plate does not extend deeper than about 19 miles (30 km). The resulting data set of subcrustal, Benioff zone earthquakes is shown in Figure 4-5. Several surface geographic points are shown for reference, but surface fault traces are left off the figure since the Benioff zone lies beneath and is separated from surface geologic faults. The Benioff zone descends in a northwesterly direction under inter- ior Alaska, through Cook Inlet and the Susitna Lowland to the Alaska Range (Biswas, 1973; Davies and Berg, 1973; Van Wormer and others, 1973). It dips gently across a wide zone, and reaches a depth of approximately 93 miles (150 km) near Mt. McKinley. Althou~h the deeper Benioff zone is discussed separately from the shallow Benioff zone, they appear to be associated with a continuous geologic unit (the subducting plate) with possible differences in associated seismicity, as discussed in Section 9. The Benioff zone increases in horizontal extent (measured in the dip direction) from west to east. It is approximately 124 miles (200 km) wide along the Aleutian Arc and attains a maximum width of approximately 291 miles (470 km) near Mt. McKinley (Figure 4-2). The northeastern limit of subduction is believed to be located at 4 -8 approximately 64.1° north latitude, 148° west longitude (Agnew, 1980), 28 miles (45 km) north of the Hines Creek strand of the Denali fault. The northwestern portion of the subduction zone has been studied in detail by Agnew (1980). He used a selected high-quality data set to contour the upper edge of the Benioff zone, and these contours are reproduced in Figure 4-5. Additional details on the Benioff zone are discussed as a product of the microearthquake study in Section 9. As shown in Figure 4-5, moderate-sized earthquakes have occurred on the Beniof zone almost directly beneath the Project sites. A magnitude (Ms) 4.7 event with a focal depth of 47 miles (76 km) which occurred on 1 October 1972 was located 6 miles (10 km) east of the Devil Canyon site and also 17 miles (27 km) west of the Watana site. An event of magnitude (Ms) 4.6 with a focal depth of 50 miles (80 km) occurred 16 miles ( 25 km) northeast of the Watana site on 28 December 1968. On 5 February 1974, a mag- nitude (Ms) 5.0 event with a focal depth of 46 miles (75 km) occurred 17 miles (27 km) southeast of the Devil Canyon site and 13 miles (21 km) southwest of the Watana site. A magnitude (Ms) 5.4 event with a focal depth of 66 miles (106 km) was located approx- imately 38 miles (62 km) northwest of the Devil Canyon site on 18 May 1975. Earthquakes recorded prior to 1964 include several large earthquakes near the sites. A magnitude (Mb) 6.1 event with a focal depth of 49 miles (79 km) occurred on 2 May 1963 17 miles (27 km) northwest of the Devil Canyon site, and an earthquake of magnitude 5.1 with a focal depth of 59 miles (95 km) occurred within 11 miles (17 km) southwest of the Devil Canyon site on 14 December 1963. 4 - 9 An interesting feature of Figure 4-5 is the region of very low seismic activity lying between the edge of the 1964 aftershock zone and the area of seismic activity to the northwest on the Benioff zone. This quiet zone does not appear to be a product of misloca- tion or error in depth of focus, since Figure 4-4, with all the seismicity data, also shows a low seismicity zone. The location of this zone is refined in Section 9 and is discussed in terms of its potential for future seismic activity. 4.3.3 -Crustal Seismici The historical record indicates that the seismicity within the Talkeetna Terrain, which lies between the Denali and Castle Mountain faults, is low. Figure 4-6 shows the data from Figure 4-4 for earthquakes with depths less than or equal to 19 miles (30 km). The shallow seismic activity is discussed in terms of four areas: the shallow Benioff zone, the Castle Mountain fault, the Talkeetna Terrain, and the Denali fault. Shallow Benioff Zone As noted above in Section 4.3.1, the events included within the area of the 1964 aftershock zone are most likely associated with the interact ion between the North American and Pacific Plates. The seismic potential of this area is best assessed in terms of seismic gap concepts, as discussed in Section 4.2. Castle Mountain Fault Five moderate to large earthquakes (magnitude (Ms) greater than 5) have occurred in the general vicinity of the Castle Mountain fault (Figure 4-6). A series of 4 events occurred in 1933 (magnitude (Ms) 5.6 to 7.0) and a large earthquake 4 -10 occurred in 1943 (magnitude (Ms) 7.3). all with assigned focal depth of zero (National Oceanic and Atmospheric Administration, 1980; Sykes, 1971). These earthquakes all took place before good station coverage existed in Alaska, and their locations and focal depths are subject to substantial uncertainty. Because of the occurrence at depth of more recent seismic activity (post 1964), it is more likely that these earlier events actually occurred at depth along the Benioff zone (Figure 4-5 shows substantial recent activity taking place at depths of 31 to 50 miles (50 to 80 km)). However, the association of this,activity in 1933 and 1943 with a surface fault, such as the Castle Mountain fault, cannot be precluded. The 1933 activity was accompanied by a large number of smaller felt events (Neumann, 1935), suggesting a shallow source in the upper Cook Inlet area. Talkeetna Terrain Four moderate earthquakes have been located at shallow depths in the Talkeetna Terrain; from west to east they are the 18 Janaury 1936 event of magnitude (Ms) 5.6, the 29 May 1931 event of magnitude (Ms) 5.6, the 3 July 1929 event of magnitude (Ms) 6.25, and the 17 July 1923 event of magnitude (Ms) 5.6. As is the case for seismicity in the vicinity of the Castle Mountain fault, these earthquakes all took place prior to the installation of regional instrumentation and are anomalous with respect to the current seismic activity that is concentrated on the Benioff zone. The location uncertainity of these events is such that, even if they occurred in the crustal zone, they cannot be definitively associated with specific faults. Additional shallow events, in the depth range 19 to 22 miles (30 to 35 km), are included in Figure 4-4. These are small (magni- tude (Ms) 4 to 5) and are widely scattered. On the basis of 4 -11 these events and the low-level crustal seismicity discussed in Section 9, the seismic environment of the Talkeetna Terrain appears very low. It should be noted, however, that the occur- rence of the 1964 earthquake may have affected the rate of occurrence of earthquakes in the Talkeetna Terrain by releasing stress regionally and 1 owering the present 1 evel of instrumental seismicity. 0 en a 1 i F au 1 t Within the study area shown in Figure 4-6, four earthquakes 1 ie along or to the north of the Denali fault. Two of these, the event of 21 January 1929 (magnitude (Ms) 6.5) and the event of 4 July 1929 (magnitude (Ms) 6.5) were recorded and located using worldwide stations. Both the epicenter location and focal depth are uncertain, but the felt reports of the January event (Heck and Bodle, 1931) suggest that it was shallow and occurred south of Fairbanks and north of the Talkeetna Terrain. The first instrumentally recorded earthquake in south-central Alaska occurred on 27 August 1904 with a magnitude (Ms) of 7-3/4; it was located at 64° north latitude, 151 • west longitude. Very few news reports were published for this earthquake, reflec- ting the sparse population of the state. Figure 4-7 presents the estimated Modified Mercalli felt intensities at locations where the earthquake was reported. The instrumental epicentral loca- tion was determined from records made in California and could be in great error. Also, the published hypocentral depth of 16 miles (25 km) is only an estimate. As shown in Figure 4-7, the earthquake appears to have been felt more strongly in western Alaska than elsewhere in the state. Thus, the epicentral location may actually be farther west than originally plotted using the teleseismic records. 4 -12 The location and geologic association of the 1904 event are very uncertain. The present data do not substantially constrain the location and it could be associated with either the Denali fault or the westernmost portion of the Benioff zone. These two sources are the most likely, since the size of the event requires association with major tectonic features. The 7 July 1912 earthquake occurred after the population and num- bers of newspapers had increased dramatically in the Alaskan interior. Felt reports and assigned intensities are summarized in Figure 4-8. The intensity pattern suggests that the earth- quake was shall01v and could have occurred on the Denali fault. The Denali fault in this area is covered with glaciers, and the observation of any evidence for recent surface breakage is unlikely. Sykes (1971) and Tobin and Sykes (1966) have associated smaller ((Ms) 4 to 5) historical earthquake activity with the Denali fault, particularly along the central McKinley strand and the trace of the Denali fault about 62 miles (100 km) east of the site region as shown in Figure 4-6. The seismic character of the Denali fault appears similar to that of the San Andreas fault in California; that is recurrent large earthquakes with major surface faulting separated by intervals of low seismic activity. The possible association of moderate to large historical earth- quakes with the Denali fault is consistent with the geologic evidence for recent displacement; thus, the seismic potential for the Denali fault is not strongly dependent on the historical seismicity. 4 -13 () 0 2 en c r -I :r> 2 -I O'l .1> Ol 01 C!l :r> 0 CD n CD 3 0" ~ , G'l NOTES C~FIC ERDC PlATE PLATE LEGEND ~;}}}t~;~ Wrangell Block Relative Pacific Plate Motion -=-=--Plate Boundary, dashed where inferred 6 6 1\ Shelf Edge Structure with Oblique Slip ----Intraplate Transform or Strike-Slip Fault Queen Charlotte Islands Fault C 1. Base map from Tarr (1974). 3. Talkeetna Terrain within the Wrangell Block :0 2. After Packer and others (1975), Beikman (1978), is shown on Figure 5-1. m Cormier (1975), Reed and Lamphere (1974), !L_ ________ ~P~Ia~f:ke~r~,~a~n~d~o~t~h:er~s~(~1~9~7~8~). ______________________________________________________________________________________________ _ PLATE TECTONIC MAP "T1 G) c JJ m .l::> NOTE 1. Modified after Davies and House ( 1979)., 0 1964 Location and year of major earthquake; rupture zones including aftershock areas are outlined ... :::: Inferred direction of motion of Pacific plate Trench axis Approximate transform plate MAJOR EARTHQUAKES AND SEISMIC GAPS IN SOUTHERN ALASKA ~L_ ____________________________________________________________________________________ __ Dam Site University of Alaska station location and name NOAA station location and name Area of coverage by USGS network (Actual station locations not shown) DE CONSULT ANTS 146!58A Decembor 1980 IMA 0 I NOTE 1. Modified after Agnew ( 1980) and Lahr ( 1980). LOCATION MAP OF UNIVERSITY OF ALASKA, USGS, AND NOAA SEISMOGRAPH STATIONS IN ALASKA 0 150 300 450 600 Kilometers FIGURE 4-3 .. J5t2._c'------p.:.j-------__;_~;;:_-----__::.!.:~~--.....S--.:f4~-rlJ'--;;:;----42.~.f"-er-...:"'i4G.so 6~ -DO IS • ·150-CO -;4 .00 54 ,QQ C) C) \3 6:5-0C C) 52.00 .C) 0 DE CONSULTANTS 14658A December 1980 C) (9 c; c; '11 (9 C) '-' c:J r!? (T', 0(9 '-/ CJC) C) + C) (') 0 C) (') C) TALKEETNA (["'-, u (9 • / (')CJ DEVIL ffi CANYON SITE I 0 C) + 100 km r~dius c:J 0 0 (9 0 ..,.--------... ........... ,,-"'' @l 'G, / / C) Q) / C)C)O CJ o / <:>C)o c:; / C&CJ©J\BC)CJ@ (T1 '--./) 0 C) CJ ANCHORAGE (!.) C) / (') LIMIT OF 1964 EARTHQUAKE AFTERSHOCK ZONE sz.oo LEGEND REP~RTEO NRGN!TUDE C) ,.0 u 7.0 0 5-D u s.o C) 4 .Q I NT ENS I TY v XI! v" <2> X <> IX 0 V{[! v "' <;) V! 0 BOUNDARY FAULTS -------Faults with recent displacement SIGNIFICANT FEATURES --------Indeterminate A feature. --.. --·--Indeterminate B feature NOTES 1. Earthquakes of magnitude greater than 4 or intensity greater than MM V are shown. 2. Magnitude symbol sizes are shown on a continuous nonlinear scale. 3. Earthquakes are listed in Appendix C. 4. Explanation of significant feature classification ·system is present:_d in Section s .. 2. 5. Explanation of alpha-numeric symbols is presented in Appendix A. 6. Number (such as 1964) next to selected epicenters is the year of occurrence. HISTORICAL EARTHQUAKES OF All FOCAL DEPTHS IN THE SITE REGION FROM 1904 THROUGH 1978 0 10 20 30 40 50 Miles E@ ;;g g;; E3 0 10 20 30 40 50 Kilometers IGURE 4-4 ···~······--~~~~~.-····-·-···.-······~···-.···-~·~----------------------------------------------- CCI C) CCI C) CCI C) CCI 62-00 C) CCI CCICb C) C) @ CCI CCI C) CCI C) CCI C) 61.00 .a a CCI CCI C) CCI C) C) CCI C)CC~+ C) CCI CCI CCI C) CCI C) C) CCI C) CCI CCI -1 .co C) CCI C) C)C)CCI C) CCI LYDE CONSULTANTS 14658A December 1980 C) CCI C) TALKEETNA Ill C) CCI CCI CANTWELL 0 ~ + ~DEVIL CANYON I SITE C9 C) CCI CCI CCI CCI C) C) C) CCI CCI C) CCIWATANA I SITE C) C) DENALI ® + + C) C) C)& CCI C) C) C) C) CCI C) C) ANCHORAGE e CCI .oa I I I I I I / I I / + CCI ,-------.... / ...... ,/'"' ~ / / CCI CCI 8c:l LIMIT OF 1964 EARTHQUAKE AFTERSHOCK ZONE LEGEND REPBRTED MAGNITUDE C) e.o (2) ?.a C) o.o C) s.o CCI •• o IX Ylt kilometers V are shOIIMl. are shown on a continuous FOCAL DEPTH SITE 1978 63.CO + CONSULTANTS 14658A December 1980 -!$(1.00 1904 C'b TALKEETNA ®/ 1933 -! 4 .oo 21 JAN 1929 . HINE.S~R.EEK ?TRA~Q_H[j 4 _7 a ------~~~==~----~== ~ MCKINLEY(') • CANTWELL + 100 km radius (~ "~J '__! ANCHORAGE 0 1933 LIMIT OF 1964 EARTHQUAKE AFTERSHOCK ZONE -62 .oo LEGEND REPCRTED H~GN!TUOE IT" 8.0 u C) 1.0 l2J s.o C) 5.0 (') '.Q HJTEN5 !TY ~> x;; <J ,, ~X v " <Y >'ill 0 "' ¢ Vl 0 BOUNDARY FAULTS -------Faults with recent displacement SIGNIFICANT FEATURES -------Indeterminate A feature --·--· --Indeterminate B feature NOTES 1. Earthquakes of magnitude greater than 4 or intensity greater than MM V are shown. 2. Magnitude symbol sizes are shown on a continuous nonlinear scale. 3. Earthquakes are listed in Appendix C. 4. Explanation of significant feature classification ·system is present~d in Section 8·2. 5. Explanation of alpha·numeric symbols is presented in Appendix A. 6. Number (such as 1964) next to selected epicenters is the year of occurrence. HISTORICAL EARTHQUAKES OF FOCAL DEPTH lESS THAN 30 km IN THE SITE REGION FROM 1904 THROUGH 1978 Alaska 4-5~3-4 156 Epicenter location tor the magnitude (Ms) 7% earthquake of 1904 Estimated felt intensity based on review of historical newspaper reports conducted for this report Denali Fault system segments A Togiak-Tikchik fault B Holitna fault C Farewell strand D McKinley strand E Hines Creek strand F Denali fault G Totschunda Fault system H Shakwak fault I Chilkat River fault 148 0-CLYDE CONSULTANTS 14658A December 1980 Northwest Territory Yukon Territory 140 NOTES British Columbia 132 ' I )sa I 54 1. Intensity is based on the Modified Mercalli Scale of 1931 (Wood and Neumann, 1931). 2. Magnitude (Ms) is from sources cited in Appendix C. 3. Denali Fault system is from Reed and Lanphere (1974) ESTIMATED MODIFIED MERCALLI FELT INTENSITIES FOR THE EARTHQUAKE OF 27 AUGUST 1904 0 100 E"""""""3 I 0 200 300 ttt: 200 400 500 Miles I E""3 400 Kilometers FIGURE 4-7 \ \ I I \ I I Alaska I I \ I \ I F I (4-t)\ \ \ \ I Gulf of Alaska 156 icenter location for the magnitude (M 5 ) 7.4 akeof1912 148 mated felt intensity based on review of histori- newspaper reports conducted for this report Felt intensity very approximate t information insufficient to estimate felt intensity o report of the earthquake being felt enali Fault system segments A Togiak-Tikchik fault B Holitna fault C Farewell strand D McKinley strand E Hines Creek strand F Denali fault G Totschunda Fault system H Shakwak fault I Chilkat River fault CONSULTANTS 14658A December 1980 \ 66 I Northwest Territory I \ \ '--"""""'--. I L~, ) L l,"' \ \ '-62 " ®3-4 \ \ '--" Yukon Territory -...., \..r...,.~\ -..... ...-...- / ~ British Columbia 58 54 140 132 NOTES 1. Intensity is based on the Modified Mercalli Scale of 1931 (Wood and Neumann, 1931). 2. Magnitude (Ms) is from sources cited in Appendix C. 3. Many aftershocks were felt following this earthquake. 4. Denali Fault system is from Reed and Lanphere 119741. ESTIMATED MODIFIED MERCALLI FELT INTENSITIES FOR THE EARTHQUAKE OF 7 JULY 1912 0 100 200 300 400 500 Miles E==l·-=-,--i-:E==c=:· ~ 0 200 400 Kilometers FIGURE 4-8 CTONIC MODEL--TALKEETNA TERRAIN region consists of a tectonic unit designated here as the etna Terrain, a sub-unit of the Wrangell Block (Figures 4-1 and The Talkeetna Terrain is defined as that region of Alaska which ounded on the north by the McKinley strand of the Denali fault, e east by the Denal i-Totschunda fault system, on the south by .Castle Mountain fault, and on the west by a zone of deformation ding from the Aleutian volcanic chain (which ends at Mt. Spurr) to (Figure 5-1). All of these crustal boundaries are faults displacement except for the western boundary which is zone of uplift marked by Cenozoic age volcanoes. The jan megathrust associated with the subducting Pacific Plate bounds ase of the Talkeetna Terrain (Figures 5-1 and 5-2). A discussion e plate tectonic framework in which the site region is located is Section 4.1 and is briefly summarized here. Pacific Plate is moving north-northwest at a rate of about inches/yr (6 cm/yr) with respect to the North American Plate and Plafker, 1980). In the region of Prince William Sound where ~oastline bends westward, there is a transition zone in which between the Pacific and North American Plates along n Charlotte Islands-Fairweather fault system is transferred to tion of the Pacific Plate along thrust faults in the northern of Alaska and the Aleutian Trench (Figure 5-1). At the southern ary of the Talkeetna Terrain, the position of the Benioff zone sts that the Pacific Plate is decoupl ing from the North American not directly interacting with one another within keetna Terrain. Most of the deformation in the Talkeetna Terrain lting from the convergence of the Pacific and North American Plates to be occurring along the boundaries of the Terrain, leaving the or region relatively free of recent deformation. 5 - 1 A broad area of deformation extending from Montague Island east to the Pamploma Ridge in the Gulf of Alaska is believed to accommodate much of the convergence between the tectonic plates. This area includes the thrust faults in the Chugach-St. Eli as Mount a ins where the 28 February 1979 earthquake (Ms) 7. 2 occurred. These structural features 1 argely accommodate the transit ion from strike-slip faulting along the eastern Gulf to the Aleutian megathrust of the western Gulf. The Castle Mountain fault is also recognized as a feature actively accommodating a small amount of convergence 'along the southern margin of the Talkeetna Terrain. In the region approximately corresponding to the trace of the Castle Mountain fault (Figures 5-1 and 5-2), the subducting Pacific Plate is decoupled beneath the Talkeetna Terrain as indicated by seismicity data (Agnew, 1980; Section 9 of this report). The deformation imparted to the Talkeetna Terrain from the Aleutian megathrust is probably expressed largely as ductile deformation, at depth, north of the Castle Mountain fault. However, recent displacement on the Denali fault north of the Terrain indicates a small amount of convergence is transmitted through the Talkeetna Terrain. The Castle Mountain fault is a right-lateral strike-slip fault with a significant component of north-side-up reverse slip (Page and Lahr, 1971; Detterman and others, 1976). Its surface expression is easily recognized between the Susitna River and the western Matanuska Valley, but its western ex tens ion beyond the Sus itna River is not well doc- umented. On the eastern end, the Castle Mountain fault apparently dies out in a series of splays, but evidence of faulting exists as far east as the Copper River basin. The northern and eastern boundaries of the Talkeetna Terrain are the Denali and Totschunda faults (the latter includes an inferred connection with the Fairweather fault), respectively. These faults are right-lateral strike-slip faults that exhibit progressively lower slip rates northward and westward from the Talkeetna Terrain as transform 5 - 2 between the Pacific and North American Plates is dissipated away he plate interaction. Motion on the Fairweather fault (southeast e Totschunda fault) of about 1.9 to 2.3 inches/yr (4.8 to 5.8 (Plafker and others, 1978) is roughly equivalent to the conver- between the Pacific and North American Plates. Much of this probably transferred through the Gulf of Alaska to the an Trench while part is distributed farther north, as only about 1.3 inches/yr (0.9 to 3.3 cm/yr) of displacement is transferred e Totschunda fault and the section of the Denali fault south of the River (Richter and Matson, 1971,; Plafker and others, 1977). A ion between the Fairweather and the Totschunda faults has been as a recently established break less than about 65,000 years (Lahr and Plafker, 1980). Near the intersection between the chunda and Denali faults, the Denali fault has a rate of displace- as high as 1.4 inches/yr (3.5 cm/yr). At the Delta River, the i fault bends westward and exhibits only about 0.4 to 1.8 inches/yr 2 cm/yr) rate of displacement on the McKinley strand (Hickman and 19 78) . Broxson Gulch thrust fault, described by Stout (1965, 1972). Stout and Chase (1980) among others, trends southwestward from Denali fault (where it intersects the Delta River) through the This feature and its southwestward continuation - Talkeetna thrust fault -is proposed to have been a major fault tern in Mesozoic through Tertiary time (Csejtey, 1980) as it accom- ated postulated differences in rates of rotation of paleotectonic its along the Denali fault (Stout and Chase, 1980). However 9 no idence of post-Tertiary displacement along the Talkeetna thrust fault Broxson Gulch thrust fault has been observed (Csejtey, 1980; Stout 1980) . the rates of displacement along faults in southern Alaska are than the rate of convergence of the Pacific Plate relative to the 5 - 3 North American Plate as discussed above. It is suggested here that a significant portion of that unaccounted-for convergence may be trans- mitted northward, even beyond the Denali fault, and is reflected at the surface in three ways: (1) as broad folds and reverse faults in the Pliocene(?) Nenana Gravels in the Nenana River valley (Wahrhaftig, 1970a, 1970b; 1970c; Hickman and others, 1978); (2) as northward thrusting along the northern front of the Alaska Range; and (3) as the overall uplift of the Alaska Range. The approximately 0.4 inches/yr (1 cm/yr) of right-lateral displacement on the McKinley strand of the Denali fault abruptly diminishes to imperceptible amounts westward from the Mt. McKinley area. The dissipation of this remaining amount of slip along the Mt. McKinley strand may contribute to ductile and brittle deformation in the interior of Alaska and the western boundary of the Talkeetna Terrain. The western boundary of the Talkeetna Terrain is ambiguous and appears to be represented by a wide zone of uplift, predominantly as ductile deformation in a broad zone, as shown in Figure 5-l. This zone, i n c 1 u d i n g the v o 1 c an o e s f r om t h e A 1 e u t i an c h a i n , was c h o s en as t he western margin because it is apparently the focal zone of uplift and deformation on the western side of the Talkeetna Terrain. The Aleutian 1 ine of volcanoes is believed to result from the down-going Pacific Plate reaching the critical depth for melting the subducted crust, resulting in magma production. This ''soft zone" in the overriding plate is an appropriate location for the remaining convergent stresses in the Talkeetna Terrain to be accommodated by uplift, plastic deforma- tion, and imbrication resulting in the broad zone of deformation shown in Figure 5-l. Although the Talkeetna Terrain is surrounded by margins subject to deformation, the interior is relatively stable and apparently behaves as a coherent unit partly decoupled from the North American Plate. The evidence for this conclusion is the absence of major brittle deformation within the Terrain that appears to be related to current stress condi- tions, and the absence of major earthquakes tht clearly have occurred 5 - 4 as discussed in Section 4. Major faults with recent been observed within the Talkeetna Terrain during tigation as discussed in Section 8. This lack of recent n leads to the conclusion that strain release is occurring along the margins of the Terrain, as shown by the major faults Totschunda, and Castle Mountain), and that the Talkeetna a relatively stable unit. 5 -5 LEGEND ~u ......--D • • • • v v v v Mapped strike-slip fault with dip slip component Mapped strike-s! ip fault, arrows show sense of displacement Mapped fault, sense of displacement not defined Inferred strike-slip fault Mapped thrust fault, teeth indicate upthrown side of block, dashed where inferred Mapped thrust fault, teeth indicate inferred upthrown side of block CONSULTANTS 14658A December 1980 MOUNTAINS Soun~ NOTES CD 0.9-2.0 cm/yr Hickman and Campbell, (1973); and Page, (1972). (2) 0.5 -0.6 cm/yr Stout and others, ( 1973) . (ll 3.5 cm/yr Richter and Matson, (1971). ® 1.1 cm/y r, no Holocene activity farther east, Richter and Matson, ( 1971 ). ® 0.9 -3.3 cm/yr Richter and Matson, ( 1971) @ Inferred connection with Dalton fault; Plafker and others, ( 1978). (/) Inferred connection with Fairweather fault; Lahr and Plafker, ( 1980). ® CID 10. 11 . 12. Connection inferred for this report. 0.1-1.1 cm/yr Detterman and others (1974); Bruhn,(1979). Slip rates cited in notes CD through ® are Holocene slip rates. All fault locations and sense of movement obtained from Beikman, Figure 5-2 presents Section A-A'. (1978). TALKEETNA TERRAIN MODEL "'T1 C) c JJ m (J1 r-:.:, 1954 Earthquake Rupture Zone NOTES 1. 2. A-A' is shown Location of Section in Figure 5-1. include those Geologic data sources in Figures 4-1 and 5-1. Plate Motion cited th American Plate Relative to Nor Lo w Historic Seismicity Zone of Benioff Zone Seismicity SCHEMATIC TALKEETNA TERRAIN SECTION REGIONAL GEOLOGIC SETTING OF THE TALKEETNA TERRAIN -Regional Geologic Setting geologic setting and geologic history of the project region are ly related to the tectonic setting of south-central Alaska as u s s e d i n S e c t i on s 4 . 1 an d 5 , a n d a s s u mm a r i z e d i n F i g u r e s 6 -1 The Talkeetna Mountains and adjacent areas are continental accreted to Alaska as part of the dominantly allochthonous terrain rising southern Alaska. This terrain has been interpreted to titute an enormous tectonic mosaic composed of separate structural s and fragments of allochthonous continental blocks accreted to the ient North American Plate during Mesozoic time (Figure 6-1 summarizes logic time units) and early Cenozoic time (Richter and Jones, 1973; ey, 1974; Jones and others, 1977; Csejtey and others, 1978; Jones Silberling, 1979). Although the exact number or even the extent of e blocks is still imperfectly known, paleontologic and paleomagnetic dies suggest that the blocks moved northward considerable distances or to collision with the North American Plate (Hillhouse, 1977; er and others, 1975; Stone and Packer, 1977). though the Talkeetna Terrain, as defined by the major structural nts bounding it (Section 5), includes the Wrangell Mountains, the a of interest for this discussion includes only the Talkeetna Moun- ins and adjacent topographic lowland areas. The Talkeetna Mountains a roughly circular mountain mass separated topographically from the aska Range by the broad glaciated Susitna Lowland and Chulitna valley to the west and northwest, respectively. The Copper River the eastern boundary (Figure 1-1). The Talkeetna are bounded on the south by the fault-controlled Matanuska central Talkeetna Mountains are extremely rugged, and are dominated heavily glaciated peaks between 6,000 and 9,000 feet (1,829 to 6 - 1 2,744 m) in elevation. To the northwest, the mountains form a broad rolling, glacially scoured upland which is dissected by deep glaciated valleys. Stratigraphy The rocks of the Talkeetna Mountains and adjacent areas can be classified in three distinct bedrock groups on the basis of age and rock type following in part the studies of Csejtey (1974) and Csejtey and others (1978). These bedrock groups· lie within a northeast- southwest structural grain and include: (1) a Mesozoic metasedimentary sequence of marine origin northwest of the Talkeetna thrust fault; (2) a northeast-southwest trending Jurassic to late Cretaceous or late Tertiary batholithic complex (including Paleozoic volcanic units) southeast of the metasedimentary sequence that forms the backbone of the Talkeetna Mountains; and (3) a late Mesozoic sedimentary and Tertiary volcanic sequence south- east of the batholithic complex (Figure 6-2). Bedrock outcrops are often 1 imited 1 oca lly because of an extensive mantle of Quaternary deposits. Therefore, interpretations of bedrock geology (such as that shown on Figure 6-2) are often inferred locally from their 1 imited exposures. However, aeromagnetic data have been used by various investigators to interpret the bedrock distribu- tion and to identify lithology contrasts across faults as discussed below. A major bedrock contrast coincides with a distinct difference in the aeromagnetic pattern in the Talkeetna Mountains. The abrupt 6 - 2 change coincides with the major northeast-southwest trending Talkeetna thrust fault and Broxson Gulch thrust fault that juxtaposes the Mesozoic batholithic complex (including Paleozoic volcanic units) on the southeast against the Mesozoic metamorphosed sedimentary sequence on the northwest (Csejtey and Griscom, 1978). Aeromagnetic data in the Copper River basin (Andreasen and others, 1964) generally indicate a parallel geologic grain that correlates with the lithology and structure of rocks exposed on the eastern Talkeetna Mountains. The Mesozoic thrust fault, deposits and metasedimentary sequence northwest of the Talkeetna includes allochthonous Triassic and Jurassic flysch autochthonous Cretaceous flysch deposits which were deposited in marine environments and subsequently metamorphosed. The allochthonous sequence, particularly in the Chulitna area (Figure 6-2), form part of a continental crustal block that was tectonically accreted to rocks of similar age and type (the Cretaceous sequence) along the margin of the North American Plate. Most of these Triassic and Jurassic rocks do not occur elsewhere in Alaska, and fossil faunas and lithologic characteristics of the rocks suggest that they were deposited as sediments in warm water at low paleolatitudes (Jones and others, 1978). Locally, the Triassic and Jurassic rocks experienced a moderate to high grade of metamorphism (amphibolite facies) as they moved northward on the Pacific Plate prior to their collison with the North American Plate. After collision occurred, the rocks were abducted northwestward onto the continental margin at least several hundred miles (several hundred kilometers (Csejtey and others, 1978)). The southwest trending ophiolitic assemblage of the upper Chulitna district is indicative of the oceanic crust squeezed up at the suture zone of the colliding blocks (Figure 6-2). The autochthonous Cretaceous flysch deposits are described by Csejtey and others (1978) 6 - 3 as a monotonous turbidite sequence of argi 11 ite and graywacke sand- stone which was probably deposited on the margin of the North American Plate. The Jurassic to early Tertiary batholithic complex includes epizonal and mesozonal plutons that underlie large portions of the central Talkeetna Mountains (Figure 6-2). Compositions range from biotite- hornblende granodiorites to tonalite (Csejtey and others, 1978). Csejtey and others (1978) indicate that the epizonal granitic rocks of Jurassic age are associated with regional metamorphism and deformation during a Jurassic tectonic event. Emplacement of early Tertiary and Cretaceous multiple intrusions is probably a product of the middle Cretaceous alpine style orogeny resulting from crustal block conver- gence; many of the plutons exhibit well-developed northeast-southwest trending shear foliation (Csejtey and others, 1978). The shearing causing the foliation is as much as 15 miles (25-km) wide and trends across the Talkeetna Mountains parallel to, and southeast of the Talkeetna thrust fault. The batholith complex is bordered on the northwest within the central Talkeetna Mountains by a Paleozoic volcanic (and metavolcanic) sequence that includes some Triassic volcanic units (Figure 6-2). This volcanic sequence is described by Csejtey and others (1978) as marine sequence of volcanic flows, tuffs, and volcanic clastic deposits which have subsequently been metamorphosed. The late Mesozoic sedimentary and Tertiary volcanic sequence (south- east of the Jurassic to early Tertiary plutons) consists of Cre- taceous, clastic shelf deposits belonging to the Matanuska Formation and a Paleocene to Miocene felsic to mafic subaerial volcanic sequence which in part overlies portions of the plutonic rocks. The volcanic sequence consists of intercalated flows and pyroclastic deposits interpreted to be vent and near-vent deposits of stratovolcanoes. 6 - 4 e. rocks are deformed by a complex pattern of normal and high-angle e faults which are part of the late Cenozoic Castle Mountain Talkeetna Mountains rocks have undergone complex and intense rusting, folding, shearing, and differential uplift with associated jonal metamorphism and plutonism. At least three major periods of ion are recognized by Csejtey and others (1978): (1) a period metamorphism, plutonism 5 and uplift in the Jurassic Period; (2) a le to late Cretaceous alpine-type orogeny; and {3) a period of al and high-angle reverse faulting and minor folding in the Period possibly extending into the Quaternary Period. deformation is characterized by emplacement of epizonal nodiorite plutons and associated regional metamorphism which ered the broad clastic marine sedimentary wedge to the north. crustal uplift caused rapid denudation of the plutons and ced a major nonconformity of the Talkeetna Format ion, an inter- .,~, ...... ~."'d Jurassic sedimentary and volcanic rock sequence located to the theast of the Talkeetna Mountains (Figure 6-2). The dominant .~ .... : ;· .ures of the middle Tertiary to Quaternary deformation are the astle Mountain fault and two normal faults in the Chulitna River the structural features in the region are a result of the ~ ....... -..v .... s orogeny associated with accretion of northwest drifting ,~.ontinental blocks to the North American Plate {as discussed in ion 4.1). This plate convergence produced a pronounced northeast- uthwest trending regional structural grain. The orogeny is typified complex folding and thrusting as these continental allochthonous cks were abducted upon the edge of the North American Plate. 6 - 5 The mountains of the Alaska Range are a product of this deformation. Deformation is particularly intense northwest of the Jurassic and Cretaceous plutonic belt. Folds are isoclinal with amplitudes from several hundred to several thousand meters, and the limbs are generally sheared or faulted out (Csejtey and others, 1978). Several episodes of the orogeny are indicated by thrust faults which not only truncate folds but are themselves folded. The Talkeetna thrust fault (including the Broxson Gulch thrust fault) is the most prominent of the Cretaceous faults within the Talkeetna Mountains. Csejtey and others (1978) indicate that Paleozoic, Triassic, and Jurassic rocks are thrust northwestward over the Cre- taceous flysch sequence on a southeast dipping fault--the Talkeetna Thrust fault. However, aeromagnetic data interpretations by Csejtey and Gri scorn ( 1978) and Gri scorn ( 1978) indicate that the southern extension of the fault south of the Talkeetna Mountain quadrangle dips northwest. Work on the Broxson Gulch thrust fault, the northern extension of the Talkeetna thrust fault, by Stout (1965) and Stout and Chase (1980) indicates that the fault also dips northwest. The age of the Cretaceous orogeny is well-bracketed by stratigraphic evidence. The youngest rocks involved are Cretaceous argi 11 ite and graywacke sandstone units that have large folds and well-developed axial plane slaty cleavage. Late Paleocene granitic plutons intrude the folded and faulted country rock including the Talkeetna thrust fault but are structurally unaffected. A slightly older upper age bracket is provided by the 61 to 75 m.y. old tonalite (or quartz diorite) pluton that cuts and is unaffected by the prominent shearing in the central Talkeetna Mountains (Csejtey and others, 1978). The most important orogenic deformations, therefore, must have taken place during middle to late Cretaceous time. Tertiary deformations are expressed by a complex system of normal, oblique-slip, and high-angle reverse faults. The Castle Mountain 6 -6 , along which the southern Talkeetna Mountains have been uplifted lly as much as 9,184 feet (2,800 m) (Detterman and others, 1976), ibits evidence of activity continuing to the present (Section 7.2). Denali fault, a right-lateral strike-slip fault (as discussed in ions 4.1, 7.2, and 8.4) exhibits evidence of fault displacements Deformation is associated with northwest convergence of the Pacific Plate with respect to American Plate as described in Sections 4.1 and 5. Regional Surface Geology end of the Tertiary Period, most of the area within the Talkeetna in was elevated to approximately its present elevations. Beginning uaternary time, slight climatic modifications altered the erosive esses, i.e., the physical weathering. These processes changed from e dominant in temperate climates to those processes characteristic lacial and periglacial environments--glacial scour, frost action, The intensity of the climatic conditions fluctuated gh the Quaternary Period, but active glaciers along the southern of the Alaska Range and the high peaks of the Talkeetna Mountains geomorphic processes are active today throughout G 1 aci ers covered about 50 percent of the present of Alaska at various times, but the area south of the Alaska crest was nearly inundated by ice (Pewe, 1975). Coalescing ice both the Talkeetna Mountains and the Alaska Range merged to form ap conditions. As a result, Quaternary to Recent deposits (includ- mantle virtually all of Alaska. These unconsolidated include fluvial, glacial, lacustrine, and colluvial deposits surface geology map (Figure 6-3) modified from Karlstrom and ers (1964) indicates that much of the mountainous and hilly regions 6 - 7 are veneered with coarse pebbly to fine-grained colluvial deposits. Intense frost shattering and solifluction, results of the rigorous climate, have produced rock and soil debris which mantle all but the steepest slopes. Glacial scouring by alpine glaciers, which followed pre-existing stream valleys, cut deep U-shaped valleys into the upland areas. Three different ages of Pleistocene drift units have been identified. Differentiation of drift units is based on position and extent of the deposits and on the degree of morphologic modification of the associated moraines. Age assignments and correlation of glacial deposits by Karlstrom and others (1964) for selected areas indicate that: highly modified moraines are pre-Illinoian; modified moraines are Illinoian; and little modified moraines are Wisconsinan (Figure 6-3). Significant morainal complexes, which define the limits of a particular glaciation or of prominent advances, are also indicated in Figure 6-3. Extensive deposits reported to be of glacio-lacustrine origin are found in the Susitna Lowland/ Cook Inlet area and in the Copper River Basin area in the southeastern part of the site region (Figure 6-3). Con- vergence of gl aci a 1 flow from the surrounding mount a ins repeatedly blocked drainage, thus producing huge proglacial lakes. The reported lacustrine deposits are finely laminated, rhythmically bedded sand, silt, and clay with ice-rafted pebbles (Pewe, 1975). Although reported as lake clay in the Cook Inlet area by Karlstrom (1964) and Karlstrom and others ( 1964), detailed studies of fossil forminifera from dri 11 core indicate the clay may be of marine origin (Hansen, 1965). Alluvial fan deposits are restricted to the north side of the Alaska Range where alpine-style glacial processes are dominant. The ter- restrial sands and gravels are confined in the upland areas between major valleys but cover broad areas north of the foothills and the northern limits of glacial deposits. 6 - 8 ial, valley train, and terrace deposits are found along the major valleys and including those downstream from active glaciers. Most the major rivers receive glacial meltwater, consequently, most deposits generally consist of unconsolidated clean sand and Valley trains are currently being formed by broad anastamosing twater streams carrying voluminous amounts of outwash debris. though terraces are similar in lithology and origin to modern valley ins, rejuvenation of river downcutting has isolated these surfaces active deposition. 6 -9 (') 0 z en c r -1 ):> z -1 en 0 "' C"l "' 3 t:T ~ ~ (0 00 0 , G) c :::0 m C) I 2600 1.8- 22.5- 65 141 195 230 280 345 395 435 502 572 -1000 -1800 -2600 -4500 - NEOGENE Normal and high angle faults developed. u 0 N 0 z UJ u PLIOCENE 1 MIOCENE Uplift of southern Talkeetna Mountains along 1------+------1 the Castle Mountain fault of approximately 2800m A>-</ OLIGOCENE <~ ~--------~ OG EOCENE ~~ ~ PALEOCENE u 0 N 0 (J) UJ :2 CRETACEOUS JURASSIC TRIASSIC PERMIAN u 0 N 0 UJ ...J <( PENNSYLVANIAN MISSISSIPPIAN DEVONIAN SILURIAN a.. ORDOVICIAN CAMBRIAN a: HADRYNIAN UJ ~ r----------------~ 1-0 HELIKIAN ON a:o a.. APHEBIAN ARCHEAN PROTEROZOIC 572 BAR SCALE (In millions of years Before Present) u 0 u u N 0 0 0 N N UJ 0 0 ...J (J) z <( UJ UJ a.. :2 u 230 650 Plutonism Continental accretion and orogenesis including faulting (reverse and thrust along NE-SW trending faults), folding, low-grade metamorphism and uplift. ~~~Piu;~~~;;;~;-;;;;--Nonconformity Vulcanism Vulcanism and sedimentation in distant terrains prior to accretion. NOTES 1. Time scale is after Van Eysinga (1978). 2. Geologic events are from data sources identified in the text. GEOLOGIC TIME SCALE "TI G') c ::rJ NOTE m en 1. Modified after Beikman (1974). I 1\.) > I{ :::J 0 ~ ra ·;:; L.. <!) 1- tJ '(5 N 0 "' Ql :2 c .~ tJ .0 '(5 E 0 N .... 0 "' Ql tJ -Ql ra L.. a.. a.. LEGEND D ~ ' ~~~{I > E0_j ~ Pleistocene to Holocene unconsolidated deposits Tertiary continental sedimentary deposits Tertiary volcanic rocks Tertiary to Cretaceous granitic rocks Mesozoic granitic rocks Mesozoic marine metasedimentary and metavolcanic rocks Jurassic marine sedimentary rocks Triassic and Permian volcanic rocks Mississippian to Permian volcanic and metavolcanic rocks Paleozoic and/or Precambrian metasedimentary rocks Tertiary to Paleozoic mafic and ultramafic rocks .. ~ ... . . ~ . ~ ----Fault, dashed where indefinite or inferred; dotted where concealed TALKEETNA TERRAIN BEDROCK GEOLOGY MAP 0 10 20 30 40 50 Miles 0 10 20 30 40 50 60 70 Kilometers NOTE "' c "' u 0 t: ·;;; 0:: Floodplain and associated low terrace deposits Outwash and valley train deposits Terrace deposits Proglacial lake deposits ~ Alluvial fan deposits ~ Relative age inferred from degree of ....,.-.,.__,....,modification of glacial moraines and drift Little modified Modified ~ Highly modified Pleistocene to Recent age deposits overlying Tertiary and older bedrock ~ Limited bedrock exposures and associated ~ coarse to fine grained deposits ~ Bedrock exposures and associated ~ coarse colluvial deposit~ ~ Significant moraine boundary 0 TALKEETNA TERRAIN SURFACE GEOLOGY MAP 10 20 ., C) c: ::0 m ~~------1_. __ M_o_d.if.ie·d--aft--er __ K_a_rl_st_r_o_m __ an_d __ o_t_h_er_s_l_1_9_6_4~)·--------------------------------------o _____ ,_o ____ 2_0----3-0----4-0----50-----6-0-----70--K--ilo_m __ a_m_r_s __ .J GEOLOGIC SETTING OF THE SUSITNA HYDROELECTRIC PROJECT REGION • Geologic Settfng of the Project Area e geologic setting and structural features characteristic of the ect area, which are shown in Figure 7-1, result from, and are an regional geologic conditions as outlined in Section . The rock types and structural elements are a function of a complex ry of deformational episodes associated with plate tectonic inter- The geologic map, modified after Csejtey and others (1978), s both the Devil Canyon and Watana sites and associated areas gure 7-1). Detailed mapping supplemented by radiometric age dating tey and others, 1978) has allowed some refinement of the rock types ages presented by Beikman ( 1974) (Figure 6-2). The only other ailed geologic study prior to Csejtey and others ( 1978) was that by ha~oorian (1974), who investigated the geology of the area about the 1 Canyon site. In addition, this area has been included as part of regional geologic and tectonic studies by numerous investigators. physiography of the area varies from rugged, steep, glacial-sculp- mountain ridges in the southeast and north to a broad, glacially red upland plateau to the west. A broad, structurally controlled tramontane basin trends northeast-southwest through the central ion of the area shown in Figure 7-1. Drainage generally parallels regional topographic grain--northeast-southwest. The Susitna River except for minor deflections, cuts obliquely across the regional 7.1.1 -Bedrock The oldest rocks in the Talkeetna Mountains occur in a northeast- southwest trending belt across the southeast corner of the Project 7 -1 area (Figure 7-1). This unnamed unit consists of a dominantly Pennsylvanian to Permian marine sequence of interlayered metabasalt to metaandesite flows and tuffs with subordinate fine-grained clastic units and has an aggregate thickness over 16,400 feet (5,000 m) (Csejtey and others, 1978). The composition and litho- logic character of the sequence strongly suggests that it repre- sents a remnant of a complex volcanic arc system (Csejtey, 1974; 1976). Regional metamorphism in early to middle Jurassic time produced low-grade metamorphic mineral assemblages. During the later alpine-type orogeny in middle to 'late Cretaceous time, the whole sequence was tightly folded and complexly faulted. Displacement along the Talkeetna thrust fault has juxtaposed these Paleozoic rocks against Mesozoic rocks to the northwest. Triassic and Jurassic metasedimentary, and metavolcanic rocks unconformably overlie Paleozoic rocks. Triassic rocks consist of a shallow-water marine sequence of amygdaloidal metabasalt flows and thin interbeds of chert, argillite, and marble in the eastern part of the Project area (Figure 7-1) and a similar sequence of inter- bedded amygdaloidal metabasalt flows and slate in the northwestern part of the Project area. The lithologies of the metabasalts are virtually identical, and these two rock sequences may have been deposited in different locales and subsequently were brought closer by Cretaceous age thrusting. Mineralogy suggests that both sequences underwent low-grade regional metamorphism associated with early to middle Jurassic plutonism and deformation (as discussed in Section 6. 1). A lower to middle Jurassic amphibolite unit lies in close proxi- mity to middle to upper Jurassic granodiorite plutonic rocks in the southeastern corner of the Project area (Figure 7-1). The amphibolite includes subordinate amounts of greenschist and foliated diorite. ·The metamorphic rocks were probably derived 7 - 2 from both the Paleozoic volcanogenic sequence and the Triassic metabasalt sequence. Adjacent to the amphibolite are dominantly plutonic rocks of granodiorite composition emplaced as multiple 'intrusions from a common magma source. Isotopic age determinations indicate emplacement took place between 150 and 175 m.y.b.p. (Csejtey and others, 1978). The northwest margin of both the granodiorite and amphibolite have been cataclastically deformed by Cretaceous aged shearing producing a pronounced northeast-southwest trending secondary foliation. The plutonic and metamorphic rocks associated with Jurassic plutonism and metamorphism were regionally uplifted and experienced subsequent rapid erosion. Material eroded from the uplifted region was deposited as a monotonous flysch sequence of 1 ower Cretaceous shale (subsequently altered to argillite) and lithic graywacke sandstone. These units· are present northwest of the Talkeetna thrust fault as shown in Figure 7-1. The 1 ithic graywacke sand- stone consists of angular to subrounded grains of fragments from aphanitic volcanic rocks~ low-grade metamorphic rocks" and fine- grained sedimentary rocks. Sedimentary structures within the flysch deposits, such as cross-stratification, are evidence for deposit ion from east and northeast source areas towards the west and southwest. These flysch deposits have undergone low-grade dynamometamorphism, complex thrust faulting, and compression into tight and isoclinal folds (Csejtey and others, 1978; 1980) as a result of the Cretaceous orogeny. Undifferentiated Paleocene granite and schist units are confined to the northeast quadrant of the Project area (Figure 7-1). These rocks consist of small granitic bodies, lit-par-lit type migmatite, and pelitic schist. Contacts among these units are generally gradational. The proximity of the schist to the small granitic bodies and the occurrence of lit-par-lit injections are suggestive of contact metamorphism in the roof zone of a large Paleocene pluton. 7 -3 Undifferentiated Tertiary sedimentary rocks are exposed along W at an a C r e e k ( F i g u r e 7 -1 ) . The r o c k s co n s i s t of f 1 u v i at il e c on - glomerate, sandstone, and claystone with thin interbeds of lignitic coal. The lack of fossil evidence precludes definitive correlation with similar lithologic units in the southern Talkeetna Mountains outside of the site region (Figure 6-2). During the late stages of the Cretaceous orogeny into early Tertiary time, northwest convergence of the continental blocks (Section 5) led to the intrusion of plutons (of different composi- tions) into the flysch and older country rocks. These plutons were intruded primarily into the Cretaceous argillite and 1 ithic graywacke sandstone sequence as shown in Figure 7-1. Radiometric age determinations of the plutons (composed of biotite granodiorite and the biotite-hornblende granodiorite) suggest they were intruded in Paleocene time approximately 56 to 58 m.y.b.p. Comparative whole rock chemical compositions indicate that these granitic rocks may be plutonic equivalents of some of the felsic volcanic rocks in the lower portion of the overlying Paleocene to Miocene volcanic rocks, discussed below. Undifferentiated Paleocene to Miocene volcanic rocks consist of a thick sequence of felsic to mafic subaerial volcanic rocks and related shallow intrusives. This sequence is present throughout the Project area (Figure 7-1). Lower parts of the sequence consist of small stocks, irregular dikes, lenticular flows, and thick layers of pyroclastic rocks ranging in composition from quartz latite to rhyolite, possibly equivalent to the Paleocene plutonic rocks described above. Upper parts of the sequence consist of gently dipping andesite and basalt flows interlayered with minor amounts of tuff. Quaternary deposits mantle much of the surface shown in Figure 7-2. A detailed discussion of these Quaternary deposits and the glacial chronology of the area is presented in Section 7.2. 7 - 4 -Structure three main structural features identified by Csejtey and others Project area shown in Figure 7-1 are the Talkeetna thiust fault, a northeast-southwest trending zone of inferred shearing and an unnamed thrust fault northwest of the Talkeetna thrust fault. These structural features are believed to be the ult of the Cretaceous orogeny associated with accretion of the rthwestward moving Talkeetna Terrain to the North American Plate ·Section 5). The accretionary process and Cretaceous orogeny oduced a pronounced northeast-southwest trending structural n which in turn controls the topography. allochthonous cant inental block was abducted onto the North ican Plate several hundred kilometers. The main thrust fault, along which most movement presumably occurred, is the Talkeetna thrust fault (including the Broxson Gulch thrust fault) (Figure 7-1). Although the Susitna feature (Turner and Smith, 1974; Turner and others, 1974) is discussed in Section 8 and identified in Figure 7-1, it was not included on the original map by Csejtey and others (1978) because Csejtey found no evidence for its existence along the suggested topographic 1 ineament (Csejtey, the Talkeetna thrust fault is poorly exposed, Csejtey and (1978) indicate a southeast-dipping fault as shown in Figure 7-1. However, interpret at ions of aeromagnetic data by Gr i scorn (1978) suggest that the possible extension of the fault southwest- ward of the Susitna River near Talkeetna dips northwest. Studies on the Broxson Gulch thrust fault, the northeast extension of the Talkeetna thrust fault, by Stout (1965) and Stout and Chase (1980) and Chase (1980) indicate this segment dips northwest. Continued studies are needed in the project area in order to determine the 7 - 5 fault orientation. Stratigraphic evidence indicates that the fault is intruded by Paleocene plutonic rocks, and overlain by Tertiary volcanic units that are structurally unaffected by the fault (Csejtey and others, 1978). These relationships suggests that movement on the Talkeetna thrust fault ceased by Pal eocene time; however, the evidence is not conclusive. The zone of Cretaceous shearing, as inferred by Csejtey and others (1978), lies parallel to and southeast of the Talkeetna thrust fault (Figure 7-1). These authors believe the zone may represent an old thrust zone of significant displacement which altered Jurassic plutonic rocks to cataclastic gneiss. Dips are generally southeast, and it is locally as much as 15 miles (25 km) wide. A . Cretaceous to Paleocene age tonalite pluton truncates this shear zone and is not affected by it, suggesting that the shear zone is pre-Paleocene in age. The unnamed thrust fault (northwest of the Talkeetna thrust fault) trends east-west in the northern portion of the project area (Figure 7-1). Along this fault, upper Triassic metabasalt flows and slate have been thrust southward over Cretaceous argillite and lithic graywacke sandstone. The metabasalt flows are similar in age and lithology to the metabasalt flows to the southeast. The two sequences may represent different facies of the same geologic terrain brought closer together by Cretaceous crustal shortening associated with convergence of the plates. 7.2 -Surface Geology of the Project Area As indicated previously in Section 6.2, much of the Project area has been glaciated in Quaternary time and is now mantled by various glacial deposits (Figure 6-3). Understanding the Quaternary chronology and 7 - 6 ion of these deposits is important for the evaluation of the or absolute age of units that may be involved in recent is investigation, the surface geology study area (designated here area shown in Figure 7-2) included both the Devil Canyon and areas and major segments of the significant features described in on 8.5 The study area shown in Figure 7-2 was selected to include area to be representative of the glacial history Project area. le infonnation is available in the published 1 iterature regarding lacial history of, or Pleistocene deposits in the Talkeetna The geology map of the Project area by Csejtey and others ) does not differentiate Quaternary sediments as shown in Figure An undated surface geology map by the U. S. Army Corps of Engi- s distinguishes till, lacustrine, and alluvial sediments, but area of the map is limited to a zone on either side of the Watana se of the lack of glacial geologic information in the site area, a liminary glacial geology study was conducted as a part of this Dr. Norman Ten Brink, of Grand Valley State College, higan, conducted a reconnaissance study of the area to identify the or Quaternary units and to develop preliminary criteria (based on thering characteristics) for relative age dating of the units. hering characteristics have been used as a consistent and reliable ative age-dating technique for the glacial deposits on the north e of the Alaska Range (Ten Brink and Ritter, 1980; Ten Brink and homas, in press). However, evaluation of weathering rates on the side of the Range suggests that weathering is much more rapid than the north side because of increased precipitation on the south side. 7 -7 During this glacial geology study, weathering data on glacial drift of known age were collected to establish a weathering-rate base line. These weathering data were used as a basis for estimating relative ages of deposits of unknown age. Data were gathered from morainal sequences in the Butte Lake area and in the area east of Stephan Lake (Figures 7-2 and 7-3) and were compared to weathering characteristics of similar glaciogenic deposits of known age in the Sik Sik Lake area and the Amphitheater Mountains (Figure 7-3). Although these data permit approximate estimates of ages for glacial deposits in the Project area, additional field data of both the base-line weathering rates and weathering parameters are needed to provide for greater confidence in the results. In order to better understand the glacial history, and to supplement Dr. Ten Brink•s work, aerial photographic interpretation from U-2 color near-infrared photographs combined with low altitude aerial reconnaissance was conducted within the area shown on Figure 7-2 to map the surface geology. On the basis of morphologic expression and geo- graphic position, various Pleistocene to Holocene glacial deposits and landforms were identified. Six types of deposits were identified: (1) bedrock with a veneer of till and erratics; (2) till; (3) glaciofluvial deposits; (4) lacustrine deposits; (5) ice disintegration drift; and (6) fluvial deposits (Figure 7-2). The following discussion summarizes the preliminary results of this study: 7.2.1 Pleistocene and Holocene Deposits Bedrock with a Veneer of Till and Erratics Bedrock of various types is inconsistently veneered by generally less than 3 feet (0.9 m) of glacial drift and scattered glacial erratics (Figure 7-2). Locally, thicker drift occurs in topo- graphic lows such as glacial grooves. Bedrock scour, par- ticularly of the uplands within the Devil Canyon area, indicates 7 - 8 that the surface was glaciated but not necessarily in Wisconsin time,. by flowing ice that produced streamline-molded forms such as wha 1 ebacks, stoss and 1 ee, crag and tail, and bedrock drumlins. Smaller scale features etched into the bedrock include grooves and striations. Landforms created by glacial erosion and deposit ion are found over much of the up 1 and p 1 ate au south of Dev i 1 Canyon . Till Ground moraine, generally thicker than 3 feet (0.9 m), and associated end moraine features cover much of the study area (Figure 7-2). Both the ground and end moraines are composed of nonstratified sand and cobbles with a silt and clay matrix, i.e., glacial till. Ground moraine is commonly characterized by large scale fluting such as in the Fog Lakes area. Concentrations of till in elongated and narrow ridges (end moraines) are common. In the study area, the end moraines include lateral, medial, recessional, and terminal moraines, These end moraines have been used to indicate glacial extent in the study area. Numerous closely nested end moraines are present (Figure 7-2) which indicate a complex history of glacial advances, retreats, and readvances. The orientation and position of end moraines within the area indicate a southward convergence of large glaciers from the Alaska Range with local glaciers that originated in the Talkeetna Mountains. Preliminary estimates of age, based on weathering data collected during this investigation, together with morphologic character- istics indicate that late Wisconsin ice reached maximum eleva- tions of 4,000 feet (1,220 m) near Butte Lake, 3,500 feet (1,067 m) near the Big Lake/Deadman Creek area, and 2,700 to 7 - 9 2,800 feet (823 to 854 m) east of Stephan Lake at the mouth of an unnamed valley (Figure 7-2). Ten Brink and Waythomas (in press) have subdivided late Wisconsin deposits north of the Alaska Range into four units, or stades, on the basis of weathering characteristics and radiometric age dates. Whether or not the characteristics of these stades can be applied to deposits from glaciers originating on the south side of the Alaska Range and the Talkeetna Mountains remains to be determined. However, four morainal sequences of inferred Wisconsin age have been identified in the Butte Lake area, east of Stephan Lake, and west of Clark Creek during this investiga- tion at locations designated as (1), (2), and (3), respectively, in Figure 7-2. Within the site region, early Wisconsin moraines are less prominent and less frequent than late Wisconsin landfonns. Small lateral morainal segments in the Portage Creek, Indian River, and Chulitna River areas as well as in area (2) are all 400-600 feet ( 122 to 183 m) higher than 1 ate Wi scans in moraines. Construc- tional Illinoian glacial deposits are not distinguishable, but Illinoian till sheets may veneer bedrock, particularly on the scoured upland plateau around the Devil Canyon site and to the south. Glaciofluvial Deposits Glacial outwash consisting of typically well-sorted sands and gravels have been deposited by pro-glacial rivers draining active glaciers. The deposits are confined to valley bottoms, usually in the form of terraces and valley trains. Watana Creek, Deadman Creek, Prairie Creek, and the Susitna and Talkeetna 7 -10 Rivers probably served as drainages for meltwater from Wisconsin glaciers and deposited extensive outwash trains. Lacustrine Deposits Lacustrine deposits form broad, flat plains and overlie glacial till in the Watana Creek area, just north of the Susitna River, and in the Deadman Creek/Brushkana Creek areas (Figure 7-2). The lacustrine silts and clays contain ice rafted gravel and cobbles and are locally interbedded with,deltaic sediments. The southern border of lake sediments in the Watana Creek area coincides with the northern edge of the fluted ground moraine. This relation- ship suggests that the side of the flowing glacial ice acted as a dam blocking meltwater derived from glaciers to the north. Ice Disintegration Drift Ice disintegration deposits scattered throughout the study area (Figure 7-2) have a characteristically hummocky kame-and-kettle morphology. These deposits, typically ice-contact ablation drift and ice-contact stratified drift, are end members of a gradational sequence of stagnant ice deposits and their composi- tion and degree of stratification are a function of the amount of reworking by meltwater. These deposits were formed by stagnant ice masses during deglaciation when glacier fronts were retrea- ting. Consequently, these deposits are valuable in understanding the glacial chronology. Fluvial Deposits Significant fluvial deposits of Holocene age are confined to valleys of larger river systems such as those of the Susitna, Talkeetna, and Chulitna Rivers. In these valleys, reworked glacial deposits and eroded bedrock material have been deposited in active floodplains and adjacent abandoned terraces. 7 -11 7.2.2-Glacial History The glacial chronology of the project area is complex. Unlike the systematic sequence of alpine glacial events on the north side of the Alaska Range, ice cap conditions and multi-directional glacial flow occurred throughout much of the Talkeetna Mountains. Glaciers from the south side of the Alaska Range pushed southward through the Deadman, Brushkana, and Watana Creek areas and the Butte Lake area to merge and coalesce with glaciers flowing from ice centers in the higher elevations of the Talkeetna Mountains. The chronology of the latest major glacial episode is better understood than is the chronology of earlier glaciations because the deposits are more frequent, prominent, and distinguishable. Closely nested morainal complexes in areas marked (1), (2), and (3) on Figure 7-2 indicate a late Pleistocene sequence of glacial advance, retreat, and readvance; however, ages of individual moraines are unknown. On the basis of this preliminary study, late Wisconsin ice is believed to have reached approximately 2,800 feet (854 m) in elevation at the Stephan Lake area and to have risen gradually northward in response to topographic gradients to 3,500-feet (1,067 m) in elevation in the Big Lake area and to 4,000-feet (1,270 m) in elevation at Butte Lake. The four subdivisions (or stades) to the late Wisconsin glaciation, as suggested by Ten Brink and Waythomas (in press) may be represented by the series of four morainal units at Butte Lake (area (1) on Figure 7-2). If that is the case, geographic position and orientation of the moraines would indicate that at least during the latest two glacial stades, ice was not thick enough to flow over the topographic pass southwest- ward toward Big Lake. Alternatively, some of the moraines near Butte Lake may represent recessional moraines as late stage glaciers retreated northward. 7 -12 gh less frequent, early Wisconsin morainal units in various of the study area suggest that ice may have reached 300 to (91 to 183 m) higher in elevation than late Wisconsin An area of glacially scoured bedrock and glacial debris bedrock above the early Wisconsin limits indicate that an lier glaciation, possibly Illinoian in age, inundated the area approximately 4,000 feet (1,220 m) in elevation on the upland north and south of the Devil Canyon site. Most drainage lies and canyons of the upland plateau are V-shaped and fluvial ~rigin, suggesting a considerable time period since the surface s last glaciated. ancestral Susitna and Talkeetna Rivers served as sediment- ' proglacial rivers draining the glaciated areas and filling with copious amounts of outwash. Decreased by decreased glacial activity, has allowed rivers to downcut and fonn river terraces. The 1 ongitudinal iles of both rivers suggest considerable fluvial modification portions of the river valleys has occurred since glaciers last errode the valleys. A small deposit of what appears to be till Susitna River valley floor in the vicinity of the vil Canyon site; this would indicate that the river valley isted prior to at least the last glaciation and that post- sitional fluvial downcutting or modification in this section of e valley is minimal. of late Wisconsin deglaciation, indi- gl ac i ers began to retreat towards their respective source Glaciers from the Alaska Range may have begun to retreat sooner, due to their distant sources, than glaciers with Talkeetna Mountain sources. Ice did flow northward toward Big Lake, probably following retreat of the Alaska Range glaciers, and formed an uate southward terminal moraine which dams Big Lake. The 7 -13 northern edge of the fluted till sheet laid down by the northwest- ward advancing glacier coincides with the southern limit of extensive lacustrine deposits which overlie till in the Watana Creek area. This ice mass acted as a dam, blocking sediment-loaded meltwater from northward retreating glaciers, thus forming a large ice-dammed, preglacial lake. Finely laminated interbeds of silt and clay deposited in the preglacial lake are locally interbedded with deltaic sediments. Similar preglacial lake conditions may have existed in the Deadman/Brushkana Creek area where extensive lacustrine sediments also overlie glacial till. Ice disintegration deposits floor many of the valleys suggesting that deglaciation was rapid and regional; many of the larger areas of deposits were formed by separation of ice fronts at topographic passes. Based on the preliminary results of this investigation, neoglacial activity appears to have been restricted to higher intermountain valleys and cirques. Fluvial processes continue to degrade and modify the Peistocene deposits. 7 -14 Postulated Susitna Feature --~c=C::::Cm::m!!~~~~~ t Thrust fault, dashed where approximately located, dotted where concealed, teeth indicate upthrown side, dip direction •nferred from Csejtey and others ( 1978i Approximate axis of intense shear zone Reported fault of unconfirmed origin and type from Turner and Smith (1974) and Gedney and Shapiro (1975) Anticline, showing crest line DE CONSUlT ANTS 14668A December 1000 45 __L_ NOTE Bearing and plunge of lineation Strike and dip of beds Strike and dip of slaty cleavage Strike. and dip of igneous flow foliation 1. Modified after Csejtey and others (1978). -N- ~ D ·c; N 0 c <l> u u 0 N 0 "' <l> ::2: u H 0 0 c <l> : ~{ <l> u g.2 <l>::2: c;; 0... <l> c <l> 8 UJ 0 .... <l> c <l> 8 ~ "" 0... <l> H u ·;:;; "' "' .._ ~ ..., LEGEND Undifferentiated surficial deposits Undifferentiated volcanic rocks Biotite-hornblende granodiorite Biotite granodiorite Undifferentiated sedimentary rocks Granite and schist Argillite and lithic graywacke sandstone Metasedimentary and meta basal tic rocks Metabasalt and slate Metabasalt to metaandesit with interbedded marble PROJECT AREA BEDROCK GEOLOGY MAP 5 10 Miles 5 10 15 Kilometers FIGURE 7-1 -------------------------------~}0~~ "' c; , tJ 0 ...... .., Qj 0:: c; c; ·;;; c; 0 tJ .. ~ "' ...... "' .J >-.~ ..... {· _c; "-O "'u Wu> ~ ~~{ "' E ·-"' ... tJ L.. Q) "' ... 1-o.. LEGEND Fluvial Deposits, stratified sands and gravels Ice Disintegration Deposits, hummocky ice-contact stratified drift to ablation tili, composition of sediments is a function of water reworking ~--Lacustrine Deposits, fine-grained silts and clay· with locally interbedded deltaic sediments Glacial Outwash, well sorted, stratified sand and gravel ~ Till, ground moraine and constructional moraines Till, lateral moraines at higher elevations and more modified than late Wisconsin moraines Bedrock, locally mantled by generally less than 1 meter of glacial drift and erratics Linear features in bedrock or glacial sediments which suggest general direction of glacial flow during Late Pleistocene glaciations TB-7-6-B0-2 ® Weathering profile sample locality and number Areas referred to in text Section 7.2 Brush kana PROJECT AREA SURFACE GEOLOGY MAP ,FIGURE 7-2 0 0 z In c ~ l> z Cil ~ 8i 111 0) l> 0 '" n 3 i , , G'l c :0 m -.....1 w STEPHAN!? LAKEV WATANA DAM SITE EAST OF II FOG LAKES Bil BUTTE LAKE DENALI LEGEND filii AMPITHEATER MOUNTAINS Bll Location of site specific preliminary Quaternary geology studies No Scale Implied LOCATION MAP OF PRELIMINARY QUATERNARY GEOLOGY STUDIES L---------------------------------------------------------------------------------------------~ S AND LINEAMENTS roduction of faults and lineaments during this study involved primarily ases or steps as summarized earlier in Figure 2-6. The first s a review of available literature and interpretation of remotely ata which led to a compilation of all mapped faults and linea- ithin 62 miles (100 km) of either Project site. Length-distance tng criteria were then applied (as described in Section 3.2) to those features of sufficient length and proximity to either site a potential impact on seismic design. In addition, a list of atures within 6 miles (10 km) of either site was compiled. ilation included all features that potentially could have an on surface rupture through either site. All features which were far away from the sites (according to the criteria) talogued, but not considered further. The result of these a group of 216 features, here called candidate • which were to be evaluated during the 1980 field reconnais- nd phase of the fault and lineament study consisted of field and the classification of all candidate features iden- d in the first step; this classification system is described tion 8.2. The third phase was the identification of candidate ificant features (described in Section 8.3). The fourth phase selection of significant features (also described below in ion 8. 3). The outcome of these phases was the ident ifi cat ion of and significant features. These faults and features are ussed in Sections 8.4 and 8.5~ respectively. 8 - 1 8.2 -Classification System For the second phase of the fault and lineament study, a classificat system was developed and adopted to permit the systematic evaluation the candidate features during the 1980 field reconnaissance. The clas sification system is based on judgments (by experienced seismic geol gists) as to whether or not a feature is a fault and whether or not t feature has had recent displacement. The geologic characteristics u to make the judgments are summarized in Table 8-1. A summary of the judgments were applied to the classification system is shown Figure 8-1. The underlying basis of the classification system is that should be given the "worst case" classification unless evidence ent that argues against that classification. For example, if a featur is a fault and has no overlying Quaternary deposits, it is classified the category that implies the highest likelihood of recent displ even though there is no evidence of recent displacement. The feature assumed to have the potential for recent displacement until evidence no recent displacement is obtained. The following discussion presents the basis for the classification sys- tem which was applied to candidate features during the field reconnais- sance portion of this investigation. The evidence used to classify these candidate features was documented using the procedures discussed in Appendix A. The consideration of candidate features classified as A, B, and BL (as discussed below) on the basis of their seismic source potential and potential for surface rupture through the Project sites is discussed in Section 8.3. Nonsi ificant Feature: The candidate feature is not a fault (applicable to lineaments only). This category includes features which could be directly related to 8 - 2 or. fluvial processes or which had conclusive evidence to tide the existence of a fault. It also includes features which judged to be the result of the unrelated alignment of 1 inear s such as ridges, v a 11 eys, vegetation, and stream segments. features, particularly those drawn on the basis of geophysics, observed at a 11 from the air or ground and were given this idence used to classify these candidate features was documented the procedures discussed in Appendix A. Nonsignificant features eliminated from any further study. Feature--Low Likelihood of Recent Displacement (BL) feature is considered to have a low likelihood of being lt and having had recent displacement (applicable to lineaments This category includes features with linear morphologic sions, but with no direct evidence of faulting in bedrock. features typically did not have morphologic expression of, or Quaternary units. terminate Feature--Low to Moderate Likelihood of Recent Dis lace- candidate feature is considered to have a low to moderate likeli- od of recent displacement. This category includes candidate fea- es which are mapped bedrock faults but which have no morphologic ession or displacement in overlying Quaternary deposits. eterminate Feature--Moderate Likelihood of Recent Dis lacement candidate feature is considered to have a moderate likelihood of displacement. This category includes mapped or observed bed- faults along which anomalous, linear morphologic relationships 8 - 3 were observed in alluvial or glacial deposits. Mapped, observed, or possible bedrock faults without Quaternary deposits suitable to assess the recency of displacement were also given this classification. In addition, features with prominent linear morphologic expressions in Quaternary units and no bedrock exposures were included in this classification. Fault with Recent Dis lacement The candidate feature is a mapped or observed bedrock fault with dis- placement in recent Quaternary units. The only fault in this category in the site region is the Denali fault. The Castle Mountain fault, immediately south of the site region is also judged to have recent displacement. No other faults which were judged to be in this category were observed in the site region. 8.3 -Selection of Significant Features The third step of the fault and lineament study was to make a prelimi- nary assessment of which candidate features potentially could be signif- icant to Project design considerations. The assessment considered the features as two discrete groups: (1) those with seismic source potential, and (2) those with the potential for surface rupture through the sites. The following preliminary significance criteria were used for this assessement. Seismic Source Potential Seismic source potential was assessed on the basis of the following criteria: (a) The Denali and Castle Mountain faults are accepted as having had recent displacement. These two faults are the only faults known 8 - 4 have recent displacement in or adjacent to the site region. faults were retained for additional evaluation. · 'Aillong the 216 candidate features reviewed during the 1980 field son reconnaissance study, none of the nonsignificant features eeds further systematic consideration. The basis for this riterion is that the nonsignificant features were judged not to be faults. Application of this criterion resulted in a of 106 features for additional evaluation. Among the rema1n1ng 106 features, all features less than 3 miles (5 km) long were not considered further. This criterion is based on the assumption that moderate to large earthquakes (Ms >5) typically do not occur on isolated short faults (or isolated faults with short surface rupture lengths). Review of available fault rupture length data (Albee and Smith, 1966; Slemmons, 1977) shows that very few faults have had surface rupture lengths less than 3 to 5 miles (5 to 8 km) during a single earthquake of magnitude (Ms) greater than 5. Applica- tion of this criteron resulted in the deletion of two additional features from further consideration. Among the remaining 104 features longer than 3 miles (5 km), those for which the estimated preliminary maximum credible earthquake (PMCE) would generate a peak horizontal bedrock acceleration less than 15% g (at either site) were not con- sidered further. This criterion used the PMCE on the Denali fault (approximately a magnitude (Ms) 8.5 event occurring a minimum of 40 miles (64 km) from the Devil Canyon site) as the limiting factor. This PMCE would produce peak horizontal bedrock accelerations of 17% to 21% g based on the results of preliminary earthquake engineering studies conducted during this investiga- 8 - 5 tion (Section 12). Consequently, features for which the esti- mated PMCE could not generate peak horiaontal bedrock accelera- tions greater than would the PMCE on the Denali fault are not expected to affect seismic design considerations. The value of 15% g was selected to accommodate uncertainties in the estimation of the PMCE for the Denali fault and the attenuation of ground motions to the sites, and to provide an additional degree of conservatism for the preliminary significance criteria evalua- tion. Using the above criteria, 46 features were identified which poten- tially could affect seismic source considerations. The discussion below of the fourth step of the study. describes the selection of the features considered to be important to seismic design considerations. Potential for Surface Rupture through the Dam Sites From the group of 106 features, an evaluation was also made of the potential for surface rupture through either Project site. The criteria used were the following: (a) Among the 216 candidate features reviewed during the 1980 field season reconnaissance study, none of the nonsignificant features needs further systematic consideration. The basis for this criterion is that the nonsignificant features were judged not to be faults. Application of this criterion resulted in a group of 106 features for additional evaluation. (b) Among the 106 features all features which were more than 6 miles (10 km) from either Project site were excluded from additional consideration. This criterion is based on the observations of the width of surface rupture zones during historic earthquakes (as discussed in Section 3.2). 8 -6 A corollary to criterion (b) is the observed length of the featur.e represents the maximum length of the feature along which recent displacement could have occurred. This length is assumed to represent half of the length of a fault (based on the assump- tion that up to half the length of a fault could rupture during a single event). This additional length was added to the observed length at the closest approach of the additional length to either Project site. If any portion of the observed 1 ength or the hypothet ica 1 additional 1 ength passed with in 6 miles (10 km) of either site, the feature was selected for further considera- tion. From the above steps, a total of 22 features were identified which may have a potential for surface rupture through either site. Of these 22 features, 20 are already considered as part of the seismic source considerations. above considerations of seismic source potential and paten- surface rupture through either site, a total of 48 features identified. These 48 features are designated candidate signifi- features. They are briefly summarized in Table 8-2. fourth step of the fault and 1 ineament study was to evaluate the idate significant features individually using the significance teria described below. This evaluation permitted refinement of the uation process. This refinement led to the selection of signifi- features, which, if they are found to be faults with recent dis- ' could have a major affect on Project design considerations should be evaluated further in 1981. evaluation of candidate significant features continued to consider features as two discrete groups. The significant criteria used r this evaluation are described below. 8 - 7 Seismic Source Potential The seismic source potential of the 48 candidate significant features was evaluated on the basis of the following criteria: (a) Their length and distance from each site. The length was used to estimate the preliminary maximum credible earthquake using procedures described in Appendix E. The distance was incor- porated into the criteria as part of the attenuation relationship of ground motions to the sites. The attenuation relationship is discussed in Section 12. (b) An assessment of the likelihood of the feature being a fault with recent displacement. This assessment is based on the classifi- cation of the features during the field reconnaissance study (described in Section 8.2). (c) An estimation of the maximum peak horizontal bedrock acceleration at each site. This criterion was developed using the preliminary maximum credible earthquake, attenuating the ground mot ions to each site using the attenuation relationship described in Sec- tion 12, and estimating the effect on Project design. Each of these criteria were broken down into individual components (for example, the classification of the features has five components·- faults with recent displacement, indeterminate A, indeterminate B, indeterminate BL, and nonsignificant). The relative importance of each component was systematically assessed. The assessments for each of the three criteria were then combined for each feature. The combined assessment for each of the 48 candidate significant features were then compared to each other and those features of potential significance to each site were selected. 8 -8 ach described above provided the methodology for systemati- incorporating preliminary data into the selection of significant The same approach was used to evaluate the potential for rupture as described below. ntia1 for Surface Ru ture Throu h the Dam Sites surface rupture potential through each site for the 48 candi- significant features was evaluated on the basis of: whether the feature passes through the either site. This criterion assesses whether a feature passes through one of the If the feature does not pass through the site. then the assessment involves judgment about how close to the site the feature passes (or twice its length passes), the orientation of the feature relative to the orientation of the proposed dam, and available information on fault type (if the feature is a fault); and an asessment of the likelihood of the feature being a fault with recent displacement in the same manner described in Item (b) for the seismic source potential evaluation. of the 48 candidate significant features was eva1 uated within of the two groups using each of the significance criteria The evaluation of each criterion was then combined an overall assessment of each feature's importance within The importance of the two groups, relative to each other~ then assessed. From a11 of these assessments~ a total combined of each of the 48 features was made. This total combined incorporates the judgments of the project geologists about importance of each of the candidate significant features due to feature's seismic source potential and potential for surface pture through the sites. 8 - 9 From the above evaluation of the 48 candidate significant features ' 13 significant features were selected for additional evaluation in 1981. The remaining 35 features are considered to be appreciably less important to the project than are the significant features. Four of the significant features are judged to merit additional evalu- ation for the Watana site and nine for the Devil Canyon site. The significant features are listed in Table 8-3. The following sections (8.4 and 8.5, respectively) discuss the faults with known recent displacement (Talkeetna Terrain boundary faults) within or immediately adjacent to the site region and the 13 signifi- cant features within the Talkeetna Terrain. Figures 8-2 through 8-5 show locations of these faults and features. 8.4 -Talkeetna Terrain Boundary Faults Denali Fault (HB4-1) The Denali fault is predominately a right-lateral strike-slip fault that is approximately 1,240 miles (2,000 km) long (Richter and Matson, 1971). The fault consists of three segments and has an arcuate east-west trend in the site region. Between the eastern and western segments of the fault (the Shakwak Valley and Farewell fault segments of Grantz (1966)) the fault divides into two traces or strands. The northerly strand is the Hines Creek strand as shown in Figure 8-2. The southerly strand, the McKinley strand, passes within 40 miles ( 64 km) north of the Watana site and 43 miles ( 70 km) north of the Devil Canyon site. The fault has been the subject of numerous studies and is generally agreed to represent a major suture zone within the earth's crust as 8 -10 by St. Amand (1957), Grantz (1966), Cady and others (1955), and Matson (1971), Page and Lahr (1971), Stout and others Forbes ind others (1973), Wahrhaftig and others (1975), and others (1978), and Stout and Chase (1980), among others. otal amount of displacement along the fault is the subject of ing discussion. Some investigators suggest the amount of slip displacement is relatively small (Csejtey, 1980), while supporting total displacements of up to 155 miles (St. Amand, 1957). of the Denali fault is believed to be the older two strands with strike-slip movement ceasing by 95 m.y.b.p. tig and others, 1975; Craddock and others, 1976). Strike-slip subsequently has principally occurred along the McKinley of the Denali fault (Wahrhaftig, 1958; Grantz, 1966; Hickman Craddock, 1973; Stout and others, 1973). Because the McKinley is the closer of the two strands to the sites, and because most major strike-slip displacement is thought to be occurring along than along the Hines Creek strand)~ the Denali (in the site region) is considered for the purposes of this igation to consist of the Farewell fault segment, the McKinley , and the Shakwak Valley fault segment as described by Grantz The fault is shown in Figure 5-1. reconnaissance of the fault in the vicinity of Cantwell during s study revealed strong morphologic expressions such as scarps, t ridges, linear valleys, and sag ponds in bedrock or surficial The prominence of the trace west of is shown in Figure 8-6. The linearity of these features the topography suggests that the fault plane is close to verti- in this area. 8 -11 Holocene age displacements along the McKinley strand have been studied by several investigators. In the Nenana River area, Hickman and Craddock {1973) find evidence for as much as 443 feet (135m) of right-lateral displacement and 10 to 13 feet (3 to 4 m) of dip-slip offset, with the south side up relative to the north side, in Holocene time. These data suggest a displacement rate of approximately 0.8 inches/year (2 em/per year) assuming that an average of 295 feet (90 meters) of displacement has occurred in the last 10,000 to 11,000 years. Stout and others {1973) measured right-lateral offsets as great as 197 feet (60 m) and as much as 33· feet (10 m) of dip-slip displacement, with the north side up relative to the south side, in Holocene units east of the Black Rapids Glacier (northeast of the site region). An estimated displacement rate based on these data would be between 0.20 and 0.24 inches/year (0.5 and 0.6 em/year) of right- lateral motion and less than 0.06 inches/year (0.15 em/year) of dip-slip motion during Holocene time. Other studies, including Plafker and others (1977), Hickman and others (1977; 1978), and Richter and Matson (1971), found evidence supporting a displacement rate between 0.4 to 1.4 inches/year (1.0 to 3.5 em/year) on the McKinley strand in Holocene time. In summary, displacement rates in Holocene time along the Denali fault locally range from less than 0.1 to 1.4 inches/year (0.25 to 3.5 em/year). There is no documentation of displacement on the McKinley strand in historic time. Hickman and others (1978) suggest the latest movement was several hundred to several thousand years ago. Review of historic seismicity during this investigation, including review of other published historical seismicity studies (e. g. Tobin and Sykes, 1966; Boucher and Fitch, 1969; Page and Lahr, 1971), sug- gests that seismic activity has occurred in the vicinity of the Denali fault. This seismicity includes microseismicity reported by Boucher and Fitch {1969) and macroseismicity (events of up to magnitude (Ms) 5 to 6 (Tobin and Sykes, 1966)). As discussed in Section 4.2, two 8 -12 e events (magnitude greated than 7) occurred in the general inity of the Denali fault. However, uncertainties in the location depth of these events preclude correlation with the Denali Denali fault has been classified during this investigation as ng a fault with recent displacement. This classification is based in the literature and observations made during this of numerous locations where Holocene units have been splaced, as well as on the prominent morphologic expression of the lt in relatively recently uplifted terrain. Denali fault is the closest fault to the sites known to have displacement. The fault affects consideration of the seismic potential for both sites. The fault does not affect con- ation of surface rupture potential through either site because of distance of the fault from the sites. Castle Mountain fault is an oblique-slip fault incorporating a nation of right-lateral and reverse motions with the north side relative to the south side (Grantz, 1966; Detterman and others, 974, 1976). The fault is approximately 124 miles (200 km) long and ds east-northeast/west-southwest about 65 miles (105 km) south of the Devil Canyon site and 71 miles (115 km) south of the Watana site igure 8-2). It is nearly vertical or steeply dipping to the north and others, 1974; 1976). fault is present as a single trace along its mapped western section in the Susitna Lowland (Figure 8-2). Along the eastern fault, in the Matanuska Valley, the fault consists of the main trace and a major splay which is known as the Caribou fault (Grantz, 1966; Oetterman and others, 1976). Detterman and others 8 -13 (1976) propose that the main trace represents the older and more fundamental break of the two traces while the Caribou fault is the trace along which late Cenozoic displacement has occurred. As is the case for the Denali fault, the Castle Mountain fault is generally regarded as a major suture zone within the earth 1 s crust. Displacement along the fault has been occurring since about the end of Mesozoic time (Grantz, 1966), approximately 60 to 70 m.y.b.p. The maximum amount of vertical displacement is approximately 1.9 miles (3 km) or more (Kelley, 1963; Grantz, 1966) and the maximum amount of strike-slip displacement is estimated by Grantz (1966) to have been several tens of kilometers, although Detterman and others (1976) cite 10 miles (16 km) as the total displacement which has occurred along the eastern traces of the fault. During aerial reconnaissance for this study, the fault was observed as a series of 1 inear scarps and prominant vegetation alignments in the Susitna Lowland (Figure 8-7). Along its eastern portion in the Talkeetna Mountains, the fault was observed as a 1 ithologic contrast and by possible offset of the Little Susitna River and other streams. Evidence of Holocene displacement is observed only in the western seg- ment of the fault in the Susitna Lowland (Detterman and others, 1974; 1976). To date, no evidence of Holocene displacement has been reported in the Matanuska Valley, although Barnes and Payne (1956) propose that up to 0.8 mile (1.2 km) of vertical displacement has occurred in the Matanuska Valley in Cenozoic time. In the Susitna Lowland, Detterman and others (1974) found evidence suggesting that 7.5 feet (2.3 m) of dip-slip movement has occurred within the last 225 to 1,700 years. This interpretation is based on a scarp and the excavation of trenches in which displaced soil horizons were observed. Carbon-14 age dates obtained from the scarp and soil 8 -14 s imply a dip-slip rate of displacement of 0.05 inch/year to inch/year (0.13 em/year to 1 em/year). Horizontal displacement the fault of a sand ridge (whose age within Holocene time is not h a s i n v o 1 v e d 2 3 f e e t ( 7 m ) o f r i g h t-1 a t e r a 1 d i s p 1 a c em e n t and others, 1974). Bruhn ( 1979) excavated two addition a 1 hes across the fault and found 3.0 to 3.6 feet (90 to 110 em) of slip displacement with the north side up relative to the south along predominately steeply south-dipping fault traces. A river ace near one of the trench locations had approximately 7.9 feet 14m) of right-lateral displacement. These displaced deposits are of Holocene age, but no age dates were reported by Bruhn no documented displacement along the Castle Mountain fault in time. Plafker (1969) reports no observed displacement during Prince William Sound earthquake (described in Section 4). A nitude (Ms) 7.0 earthquake occurred in the vicinity of the Castle tain fault west of Anchorage in 1933 (Figure 4-6 and Appendix C). is not known if the earthquake was related to the Castle Mountain , and no investigations to look for surface displacements have reported (Page and Lahr. 1971). others (1976) have reviewed historical seismicity in the cinity of the fault for the time period 1934 through October 1974. of the events in the vicinity of the fault have reported focal s of more than 19 miles (30 km) with the precision in hypocenter s estimated by the authors to be up to~ 12 miles (20 km). The of these events suggests that the events may be occurring at below the crust. In summary, there has been seismic activity in vicinity of the fault but no reported correlation of earthquakes 8 -15 The Castle Mountain fault has been classified during this investiga- tion as being a fault with recent displacement. This classification is based on the morphologic expressions of the fault in Holocene deposits and the reported displacements in trenches excavated across the southwestern portion of the fault. The fault dips steeply to the north or south, or is near-vertical. The sense of displacement is one of oblique displacement comprised of north side up relative to the south side, and right lateral components. The Castle Mountain fault is not expected to' affect consideration of the seismic source potential or the surface rupture potential for either site. The Denali fault is closer to the sites than the Castle Mountain fault and has .the potential for a larger earthquake (on the basis of considerations presented in Sections 11 and 12). Consequently, the seismic source potential of the Castle Mountain fault is considered to be significantly less than that of the Denali fault and therefore does not affect seismic source considerations. The Castle Mountain fault is too far from the sites to affect po- tential surface rupture considerations. The fault has been included in these discussions because it is a Talkeetna Terrain boundary fault with recent displacement and is immediately adjacent to the site region. Benioff Zone As discussed in Section 4.1, the Pacific Plate is moving northwestward at a relatively faster rate than the North American Plate. Along the Aleutian Trench in the Gulf of Alaska, the differential rate of move- ment is accommodated by subduction or underthrusting of the Pacific Plate beneath the North American Plate. The subducting Pacific Plate dips beneath Alaska to a depth of approximately 93 miles (150 km) as discussed by Packer and others (1975); Davies and House (1979), Agnew (1980), and Lahr and Plafker (1980). 8 -16 Evidence for the subducting Pacific Plate is the zone of seismicity associated with the plate. This zone of seismicity, the Benioff zone, has been observed in the site region by Davies (1975) and Agnew (1980) and is reported in the results of this investigation (Section ; Figure 9-9). Southeast of the site (apparently beneath the Matanuska Valley region), the Benioff zone becomes decoupled from the North American Plate and increases in dip as discussed in Sect ion 4.3.3 and shown in Figure 5-2. Northwest of the area of decoupling, a transition zone lies between the Benioff zone and the crust. Hypocentral data obtained during this investigation show the Benioff zone to be at depths of 31 (50 km) and 37 miles ( 60 km) beneath the Watana and Devil Canyon sites, respectively (Figure 9-9). The Benioff zone is considered to be a source of seismicity for both sites. This judgment is based on the association of earthquakes with the downgoing slab and the latter's proximity to the sites. The zone is not considered to affect consideration of surface rupture potential through the sites because of the depth of the zone and the decoupling from the crust at the site. The effect of the Benioff zone on the seismic source potential for both sites is discussed in Section 12. 8.5 -Significant Features 8.5.1 -Watana Site Talkeetna Thrust Fault (KC4-1) The Talkeetna thrust fault is a reverse or thrust fault which trends northeast-southwest and passes 4 miles ( 6. 5 km) east of the Watana site (Figures 8-2 and 8-3). The length of this fault is at least 54 miles (87 km) and may be as long as 167 miles (270 km) if it is continuous with the Broxson Gulch thrust fault in 8 -17 the northeastern part of the site region (as shown by Beikman and others ( 1974)). Southwest of the sect ion of the Sus itna River which passes through the sites, the fault is believed to continue based on magnetic anomalies as well as bedrock mapping (Csejtey and others, 1978; Csejtey and Griscom, 1978). The dip of the fault is uncertain. Csejtey and others ( 1978) show the Talkeetna thrust fault dipping to the southeast. Inter- pretation of aeromagnetic data by Csejtey and Griscom (1978) sug- gest a southeast dip. Smith (1974) and Turner and Smith ( 1974) do not show a dip on the fault. The Broxson Gulch thrust fault, apparently continuous with the Talkeetna thrust fault, is be- lieved to have a northwest dip by several of the investi- gators who have examined the fault or compiled information for it (e. g., Turner and Smith, 1974; Stout and Chase, 1980), although Csejtey and others (1980) imply a southeast dip. Evidence for fault displacement strongly suggests that the fault developed as a major thrust zone along which the front of an accreting land mass collided with the depression lying on the southern margin of the North American plate in Mesozoic time (Csejtey, 1980). The result, based on current interpretations, is that the volcanic units southeast of the fault were thrust upon or beneath the flysch deposits of argillite-graywacke sandstone in the site region (Section 6-1; Figure 6-2). Stout and Chase (1980) and Chase (1980) have observed 01 igo- cene sediments and dikes offset by the Broxson Gulch thrust fault. They postulate that 33 miles (54 km) of northwest-over- southeast thrust faulting has occurred since 38 m.y.b.p. At the southwestern end of the Talkeetna thrust fault, Csejtey and others (1978) report that the fault is overlain by Tertiary volcanic units which are not faulted. Smith (1980a; 1980b) 8 -18 rts evidence of the fault in units of Jurassic age in the of the Sus itna River where at 1 east two es of the fault are present. d studies conducted along the fault during this investigation showed that faulting has occurred in volcanic units of reported Tertiary or Triassic age on the south bank of the Susitna River, proximately 1.5 miles (3 km) downstream of Watana Creek. In. the Windy Creek region northeast of the town of Denali, sedimentary strata of reported Jurassic age were observed to be faulted against volcanic units of reported Triassic age (Turner 1974). Bedrock notches, scarps, and saddles, strongly of bedrock faulting, are also present along the north near the head of Windy Creek. Unlithified, semiconsolidated sediments possibly of Quaternary age were observed on the north side of the Susitna River (during this investigation) to have anomalous relationships suggestive of possible fault displacement. Some of these relationships could also be related to slumping or smallscale landslides. As shown in Figure 8-8, exposures of these deposits are adjacent to westward . dipping sedimentary units of inferred Tertiary age. The age of both deposits is uncertain based on available data. The Quaternary age is based on the unconsolidated nature of the sediments. The Tertiary age is based on the proximity and visual similarity to Tertiary units exposed in Watana Creek (Figure 7-1). The fault shows little morphologic expression in surficial units in the vicinity of the Susitna River. A very subtle alignment of relief was observed during some 1 ight ing conditions but was not observed repeatedly under similar or different conditions. 8 -19 Two clusters of microseismic activity were observed east of the Talkeetna thrust fault near Grebe Mountain (Figure 9-1) as discussed in Section 9.3. The events are approximately 6 miles (10 km) east of the surface trace of the fault and at a depth of 6 to 12 miles (10 to 20 km). Focal plane mechanisms obtained from one of the clusters suggest that one of the failure planes (fault rupture planes) is oriented northeast-southwest, dips northwestward, and has a reverse (thrust) sense of displacement (Figure 9-7). No consistent motion could be determined for the second cluster (Section 9.3). The depth ~f the events, the locations of the events, and the orientation of the postulated fault-rupture plane suggests that the microearthquake activity is not directly related to the Talkeetna thrust fault. In addition, the fault rupture plane associated with the microearthquake activity is small (less than 0.4 mile2 (1 km2)) and would not be expected to be in spatial proximity to the Talkeetna thrust fault. The microearthquake activity could possibly be associated with a small, subsurface fault which is conjugate to the Tal- keetna thrust fault. There are however, few data available to adequately evaluate this hypothesis and to convincingly support the hypothetical relationship. The fault has been classified during this investigation as being an indeterminate feature with a moderate likelihood of recent displacement (A). This classification is based primarily on: its being mapped as a major bedrock fault; the associated aero- magnetic anomaly; evidence of related shearing in volcanic units; evidence of a shear zone along Butte Creek north of the Susitna River; bedrock notches near the head of Windy Creek; Jurassic sedimentary units faulted against Triassic volcanic units in Windy Creek; and anomalous relationships in sedimentary units (of possible Tertiary age) on the north side of the Talkeetna River. 8 -20 fault has been designated as a significant feature because of seismic source potential for the Watana and Devil Canyon It is a long feature which passes near the Watana The fault does not affect consideration of potential face rupture through the Devil Canyon site because it does at pass through the Devil Canyon site. It is not expected to consideration of potential surface rupture through the fana site unless studies conducted in 1981 encounter fault ~ates west of the presently mapped location, a northwest dipping lt plane, and/or evidence of recent displacement. Susitna feature is a postulated northeast-southwest trending t that is 95 miles (153 km) long and approaches to within 2 les (3.2 km) of the Watana site (Figure 8-2 and 8-3). The was first described by Gedney and Shapiro (1975) as a topographic lineament which they observed on LANDSAT These authors postulated that the lineament was a fault in part on data assembled by Turner and Smith (1974) ich is described below and also on the basis of their inter- of seismic activity in the vicinity of the southern feature. Evidence that the feature is a fault has been inferred by Turner and Smith (1974) in the West Fork area of the south flank of the Alaska Range (Figure 8-2). The inference is based on K-Ar dates on plutonic bodies and interpreted cool-down rates associated with these plutons (Smith, 1980b). According to this hypothesis, the plutonic units on the east side of the Susitna feature. cooled down more rapidly than those on the west side of the feature suggesting that the latter was at greater depth than the fanner and subsequently was faulted up into contact with the units that cooled down more rapidly. 8 -21 Smith (1980b) examined the Butte Lake area and did not find evi- dence of a fault. In addition, he has not observed evidence of the Susitna feature as a fault anywhere besides the West Fork area. Gedney and Shapiro (1975) report that the Susitna feature corre- sponds to the eastern boundary of the metasedimentary units in the project area (those presumably shown by Csejtey and others (1978) as being Cretaceous age argillite and graywacke sandstone (Figure 7-1)). Gedney and Shapiro (1975) also suggest that there is seismic activity associated with the Susitna feature. In particular, they site a magnitude (Mb) 4.7 event and a mag- nitude (Mb) 5.0 event which occurred on 1 October 1972 and 5 February 1974, respectively. The location given by Gedney and Shapiro (1975) shows the earthquakes to be spatially close to the surface trace of the Susitna feature and to suggest a right- lateral strike-slip sense of displacement. Review of these earthquakes during this investigation however, showed that with the error bars in location reported by Gedney and Shapiro (1975), the two epicenters could be more than 8 miles (13 km) from the feature and the focal depths put the events at depths of 46 to 47 miles (75 to 76 km) (as summarized in the historical earthquake catalog in Appendix C). Even with the imprecision associated with focal depth determinations. these events appear to have occurred at depth, on the Benioff zone. The correlation of these events with the Susitna feature appears to be questionable. The seismicity near the southern end of the feature could conceivably be associated with the feature, but there is little evidence to support this association. Csejtey and others (1978) report finding no evidence for the postulated Susitna feature, and no evidence of a fault was observed during this investigation. No evidence of a bedrock 8 -22 nault was observed in Tsusena Creek which is the only location with good bedrock exposures long the entire length of the No morphologic expression was observed along the entire of the feature which is suggestive of either a fault or recent displacement (Figure 8-9). This feature has been classified during this investigation as being indeterminate with low 1 ikel ihood for recent displacement (BL). This classification is based primarily on the reported by Turner and Smith (1974) and the inferences by Gedney and Shapiro (1975) which suggest that a fault could be present. In contrast, there is strong circumstantial evidence to suggest that the Susitna features may not be a fault and does not have recent displacement. This evidence includes the reported absence of a fault by Csejtey and others ( 1978); the absence of any evidence observed during this investigation for a fault or for recent displacement; and the absence of any correlation between micro- earthquake activity and the feature based on results obtained during this investigation. Its origin, if the feature is not a fault, may be related to glacial modification and enhancement of aligned pre-glacial stream valleys. The feature has been designated as a significant feature despite the absence of evidence that the feature is a fault. This designation results from the length of the feature and its proximity to the Watana site. Therefore, the feature is included for additional study in 1981 because of possible seismic source potential and possible potential for surface rupture through the Watana site. The feature does not affect consideration of seismic source potential and potential surface rupture at the Devil Canyon site because of its distance from the Devil Canyon site. 8 -23 Additional studies are therefore considered necessary to verify that the Susitna feature is not a fault. If the feature should be found to be a fault, then additional studies will need to be considered to determine the related fault parameters and the recency of displacement as discussed below for lineament KD3-7. If the lineament is not a fault, then it will no longer affect consideration of seismic source potential and potential for surface rupture at the Watana site. Lineament KD3-7 Lineament KD3-7 trends approximately east-west along the Susitna River for a distance of 31 mi 1 es (50 km) , At its western end. the 1 ineament passes through the Watana site (Figure 8-3). The lineament was identified by Gedney and Shapiro (1975) on LANDSAT and SLAR imagery. At the scale of the imagery~ the 1 ineament approximately corresponds to a series of somewhat linear sections of the Sus itna River between approximately the confluences of Tsusena Creek on the west and Jay Creek on the east. During this investigation, virtually no evidence of a major through-going lineament was observed. Approximately 6 miles (10 km) upstream from the Watana site, the lineament is shown by Gedney and Shapiro (1975) to cut across the south bank of the Susitna River and to trend across the low plateau northwest of Mt. Watana (Figure 8-3). On this plateau linear surficial glacial features which trend oblique to the lineament's trend are clearly continuous and show no indication of either a crosscut- ting lineament or fault (Figure 8-10). Thus, no morphologic expression of the lineament was observed on the plateau. No evidence of structural control was observed on the Sus itna River where the 1 i neament is shown by Gedney and 8 -24 ( 1975) to cut across the river bank. Drilling results, rted by the U. S. Army Corps of Engineers (1979, plates D-34 D-35) show shear zones 3 to 14 feet (1 to 4 m) wide in the Preliminary results of drilling in vicinity of the lineament conducted during 1980 for Acres not preclude the presence of a through-going es; however, there is no evidence of a major structural ament KD3-7 has been classified during this investigation as fng an indeterminate feature with a low likelihood of recent isplacement (BL). This classification is based on the absence any evidence that the 1 ineament is a fault or that there is ~sible recent displacement. The feature has been retained for additional study primarily on the basis of its proximity to the There is virtually no geologic evidence that suggests the lineament is a fault. The lineament has been designated as a significant feature because it is shown to pass through the Watana site and is of moderate length. Consequently, the lineament theoretically could affect consideration of seismic source potential and surface rupture potential of the Watana site. The lineament does not affect consideration of seismic source potential nor potential surface rupture at the Devil Canyon site because of its distance from the Devil Canyon site. Additional studies are considered necessary to determine if lineament KD3-7 is a fault. If it should turn out to be a faultg then detailed studies will need to be considered to determine the recency of displacement as well as other pertinent fault parame- ters (such as the amount of displacement, type of displacement, orientation, etc.) If the lineament is found not to be a fault, 8 -25 then it will no longer effect consideration of seismic source potential or the potential for surface rupture at the Watana site. The Fins feature is a shear zone which trends northwest-southeast between the Susitna River and Tsusena Creek and is nearly vertical (Figure 8-3). The feature is 2 miles (3.2 km) long and is shown as a fault or shear zane dipping 70" to 75° to the northeast on an undated U.S. Army Corps of Engineers Alaska District map (Plate 05 entitled 11 Watana Reservoir Surficial Geology"). The Fins feature is prominently exposed on the north side of the Susitna river as a series of vertical shear zones which has a total width of approximately 200 feet (61 m). The shear zone is approximately 2,500 feet (762 m) upstream from the proposed Watana dam axis and is in a granitic unit (specifically, a dioritic pluton) mapped as being Paleozoic in age by Csejtey and others (1978) as shown in Figure 7-1. Evidence of the feature has not been observed on the south side of the Susitna River. However, the south bank does not have the prominent bedrock exposures which are present on the north bank in this area. The Fins feature observed on the north bank of the Susitna River appears to correlate with a moderately to highly weathered~ oxi- dized shear zone present on the northeast bank of Tsusena Creek approximately 2 miles (3.2 km) upstream from the confluence with the Susitna River. Joint measurements were obtained during the 1980 field season by Acres American Inc. on the Susitna River (location WJ-3) and by both Acres American Inc. and Woodward- Clyde Consultants in Tsusena Creek (locations WJ-4 and JW-3. 8 -26 '"'~c7i'!'~------------- ively). These measurements show a prominent northwest- east trending set of joints which dip steeply northeast to hwest. Observations during this investigation at Tsusena Creek included that of a 6.5-foot-(2-m-) wide fault zone (within the oxidized !zone) which is oriented N30°W and dips 72°NE. The fault zone is n granitic units of reported Paleocene age (Figure 7-1) and ~contains mylonite and possibly pseudotachylite. Elsewhere the oxidized zone, small scale faults oriented northwest- ast with a northeast dip and slickensides were observed. oxidized zone is shown in Figure 8-11. No evidence of the feature was observed northwest of the Tsusena Creek exposure; however, prominent exposures similar to that at Tsusena Creek are lacking. feature appears to underlie a morphologic depression in surficial units between the Susitna River and Tsusena Creek. It is also coincident, in part, with a buried paleochannel which is filled with glacial deposits. Evidence for the paleochannel is based on seismic refraction studies conducted by Dames and Moore (1975) and Woodward-Clyde Consultants (1980). The Fins feature has been classified during this investigation as being an indeterminate feature with a moderate 1 ikel ihood of recent displacement (A). This classification is based primarily on the observed shear zones in the Sus itna River and Tsusena Creek and on the morphologic depression in glacial sediments that appears to coincide with the feature. The feature has been designated as a significant feature because of its proximity to the Watana site and resultant surface rupture potential through the site. The feature is considered to be too 8 -27 ~"'"""'' _____________ _ short to affect consideration of seismic source potential (as discussed in Section 2.4.2). The feature does not affect seismic source or surface rupture considerations for the Devil Canyon site because of its distance from the Devil Canyon site. 8.5.2 -Devil Canyon Site Lineament KC5-5 Lineament KC5-5 trends north-northwest/south-southeast for a dis- tance of 12 miles (20 km) and approaches within 4.5 miles (7 km) east of the Devil Canyon site (Figure 8-5). The 1 ineament was initially identified in part by Gedney and Shapiro (1975) on LANDSAT imagery. Subsequent examination of U-2 photography and aerial reconnaissance during this investigation resulted in the extension of the lineament at its northern and southern ends. The lineament is expressed morphologically as a 1 inear stream drainage and low saddle or shallow depression south of the Susitna River and as a linear stream drainage north of the Susitna River (Figure 8-5). North of the Susitna River, the lineament was observed during the field reconnaissance study to be expressed as a broad linear valley with small lakes and ponds. This valley and related stream drainage align with a tributary stream valley south of the Susitna River. This stream has a bedrock fault exposed in the bottom of the valley near the confluence with the Susitna River. From the air, the fault was observed to be expressed as a sheared zone of oxidation (and perhaps mineralization) within granitic bedrock. Access lim it at ions prec 1 uded a ground study of the fault. 8 -28 the southern end of the 1 ineament, a step or scarp was ed (Figure 8-12). Ground reconnaissance of this scarp that joints at the outcrop are oriented parallel to the orientation of the lineament (NlOoW). Decomposed igneous rock is present at the top of the scarp and hard, strong rock is present at the base. A discontinuous cover of till overlies the ground surface in the vicinity of the scarp. The scarp appears to be related either to joint control or possible slumping. No of fault control was observed. The lineament appears to be controlled by a bedrock fault along at 1 east part of its 1 ength and by joint control or slumping along its southern section. No evidence of recent displacement was observed. However, the paucity of geologically recent deposits precludes a definitive evaluation of the recency of displacement based on the results of the investigation to date. Lineament KCS-5 has been classified during this investigation as being an indeterminate feature with a low to moderate likelihood of recent displacement (B). This classification is based pri- mariy on the presence of bedrock faulting locally along the lineament and the general lack of deposits suitable for determi- nation of the recency of displacement. The lineament has been designated as a significant feature because of its seismic source potential for the Devil Canyon site. The lineament does not affect consideration of the poten- tial for surface rupture of either the Devil Canyon or Watana sites because it does not pass through the sites. The lineament does not affect consideration of seismic source potential at the Watana site because of its distance from the Watana site. 8 -29 Additional studies are considered necessary to determine if the exposures of apparent faulting are related to the 1 ineament and what portion of the 1 ineament is fault controlled. If the 1 inea- ment or portions of the lineament are fault controlled, then studies need to be cons ide red to determine the related fault parameters and recency of displacement as discussed above for lineament KD3-7. If the lineament is not a fault, or is fault controlled over a significantly shorter length than its present mapped length, then it will no longer affect consideration of seismic source potential at the Devil Canyon site. Unnamed Fault An unnamed fault has been mapped by Richter (1967) for a distance of 3 miles (5 km). As described by Richter (1967) the fault is oriented N70°E, dips 30°NW, and approaches within 3.5 miles (5.6 km) northwest of the Devil Canyon site (Figure 8-5). Richter mapped the fault as having normal displacement which downdropped argillite on the northwest relative to quartz monzonite on the southeast (the age of these units is Mesozoic and Cenozoic, respectively, as shown in Figure 7-1). The fault is marked by clay gouge, slickensides, and limonite (orange to yellow iron oxide) stain. The fault was observed on U-2 photography during this investiga- tion to be a short, linear depression with a prominent oxidized zone with shearing at the southwest end of the depression (Figure 8-13). Aerial and ground reconnaissance during this investiga- tion showed evidence of faulting in the argillite in the vicinity of the oxidized zone. The age of the youngest unit involved in the faulting, the Cenozoic granodiorite 9 suggests that the displacement has oc- curred in the last several million to tens of millions of years. 8 -30 ~-------------------------- ~ppropriate to determining how recent the displacement urred, within this Cenozoic time framework, was not obtained ing this investigation. KDS-2 has been classified during this investigation as ing an indeterminate feature with low to moderate likelihood of nt displacement (B). This classification is based on the esence of a mapped fault along which there is no prominent morphologic expression. The fault has been designated as a significant feature because of its seismic source potentia 1 for the Dev i 1 Canyon site. The T.ineament does not affect consideration of the potential for e fault rupture through either the Devil Canyon or Watana site~ because it does not project through these sites, nor does it affect consideration of seismic source potential at the Watana site because of its distance from the Watana site. Additional studies are considered necessary to better define the length of the fault and to locate units or surfaces of suitable age to better define the time of latest displacement along the fault. In addition, the relationship of these units or surfaces relative to the fault should be evaluated to determine the recency of displacement along the fault. If the fault is found to be shorter than its present length or is found to have evidence that no recent displacement has occurred, then it will no longer affect consideration of seismic source potential at the Devil Canyon site. Lineament KDS -3 Lineament KDS-3 trends northeast-southwest for a distance of 51 miles (82 km) and approaches within 3.6 miles (5.8 km) northwest 8 -31 of the Devil Canyon site (Figures 8-2 and 8-4). Part of the lineament is identified as a fault by Kachadoorian and Moore (1979). The remainder of the lineament was identified by Gedney and Shapiro (1975) on SLAR and LANDSAT imagery. Subsequent examination of U-2 photography during this investigation showed the lineament to be expressed morphologically as a prominent 1 inear segment of Portage Creek and as a prominent 1 inear bench along the south bank of the Susitna River southwest of Portage Creek. Ground and aerial reconnaissance studies conducted during this investigation along Portage Creek showed the lineament to consist of a prominent 1 inear, elevated depression along the northwest bank of Portage Creek (Figure 8-14). At the northeast end of the lineament, mineralized zones were observed in Portage Creek. Further to the south, along the northwest side of the creek, an apparent shear zone was observed which could not be reached on the ground. The shear zone may be related to the lineament, although that observation remains to be confirmed. Elsewhere along this linear depression, it appeared to be underlain by bedrock and to represent a glacial meltwater side channel. Near the confluence of Portage Creek and the Susitna River, the lineament trends across a low plateau and is expressed as a bench or terrace. Some mining activity is being conducted on this plateau. The nature of the mine and the geologic relation- ships exposed in the mine were not available at the time of this report. No evidence of fault control was observed in intermittent rock exposures and river alluvium where the lineament crosses the Susitna River; however, folding in argillite and sandstone was observed southwest of Portage Creek. From this area to Gold 8 -32 Creek, the lineament is represented by a meltwater side channel in glacial moraine deposits along the south bank of the Susitna River. South of Gold Creek, the lineament is expressed in bed- rock as a bluff or terrace along which there was an observed consistent pattern of stream deflections or offsets. In the vicinity of Curry, a pronounced change in lithologic texture and color and perhaps structural fabric was observed. In addition to the observations described above, there is circum- stantial evidence which suggests· that another lineament (desig- nated KD6-4 during this investigation) may be a splay of lineament KD5-3. Lineament KD6-4 is a lineament identified on LANDSAT and SLAR imagery by Gedney and Shapiro ( 1975). The 1 ineament trends east-west along most of its length and northeast-southwest at its eastern end. The eastern end of the lineament (as it is presently observed). lies parallel to lineament KD5-3 and on the opposite (north) side of the Susitna river. Evidence of possible bedrock faulting was observed along sect ions of the 1 ineament, and there are local anomalous morphologic relationships in glacial units (e.g., deeply eroded drainage channels with no observed source). On the basis of observations made during field reconnaissance for this investigation, it is considered possible that lineament KD6-4 is a splay of lineament KD5-3. For the purposes of additional evaluation, lineament KD6-4 will be considered and designated as the southwestern splay of lineament KD5-3. Lineament KD5-3 and the southwestern splay have been classified during this investigation as being an indeterminate feature with low to moderate likelihood of recent displacement (B). This classification is based on: local expressions of mineralized and shear zones along the lineament which are suggestive of fault control; the fault segment shown by Kachadoori an and Moore ( 1979) 8 -33 that corresponds with a portion of the lineament; the presence of mining activity suggestive of possible fault control; and the lithologic contrast at the southwestern end of the lineament. There is no evidence of displacement in glacial and fluvial deposits along the lineament, and many segments of the lineament appear to be related to glacial processes. Thus, there is local evidence of bedrock fault control along sections of the lineament and few data which serve to define the recency of displacement. The lineament has been designated as a significant feature because of its seismic source potential for the Devil Canyon site. The lineament does not affect consideration of the poten- tial for surface rupture through either the Devil Canyon or Watana sites because it does not project through these sites, nor does it affect consideration of seismic source potential for the Watana site because of its distance from the Watana site. Additional studies are considered necessary to determine if lineament KDS-3 is a fault. If it is a fault then detailed studies will need to be considered to determine the related fault parameters and recency of displacement as discussed above for lineament KD3-7. If the lineament is not a fault, then it will no longer affect consideration of seismic source potential at the Devil Canyon site. Lineament KDS-9 Lineament KD5-9 trends west-northwest/east-southeast for a dis- tance of 2.5 miles (4 km) and approaches within one mile (1.6 km) south of the Devil Canyon site (Figure 8-5). The lineament initially was identified on SLAR imagery by Gedney and Shapiro (1975). Subsequent examination of U-2 photography during this investigation showed the lineament to be expressed morpholog- ically as a linear alignment of a stream drainage, several small lakes, and marshland. 8 -34 The western segment of the lineament, expressed by the stream ainage, cuts across the structural grain of the terrain in . which it is located. Along the middle segment, the lineament is expressed as linear shoreline. Locally, the lineament is expressed as a glacial trimline (Figure 8-15). Glacial moraine deposits were observed between two of the lakes along the align- ment; no evidence of fault displacement was observed in these deposits. East of the lakes, the lineament is a shallow depression which aligns with a knickpoint (with waterfalls) in Cheechako Creek. Where the lineament was examined on the ground (approximately 0.6 miles (1 km) west of the intersection with lineament KD5-45). the orientation of schistosity was observed to be parallel with the alignment of the lineament. The lineament is classified as being an indeterminate feature with low likelihood of recent displacement (BL). This classi- fication is based on the judgment that this lineament did not have any clear-cut evidence of fault control. There is circum- stantial evidence suggestive of fault control, e.g., the knick- point in Cheechako Creek. These is also circumstantial evidence that even if the lineament is a fault it does not have recent displacement because glacial moraine deposits are not displaced. However, definitive evidence which precludes the presence of a fault and which precludes recent displacement has not been obtained. The lineament has been designated as a significant feature on the basis that it could affect consideration of seismic source potential at the Devil Canyon site. The lineament does not affect consideration of surface rupture potential through the Devil Canyon site because it does not pass through the Devil Canyon 8 -35 site. The lineament does not affect consideration of seismic source potential or potential surface rupture at the Watana site because of its distance from the Watana site. Additional studies are considered necessary to determine if lineament KDS-9 is a fault. If it is a fault then detailed studies will need to be considered to determine the related fault parameters and recency of displacement as discussed above for lineament KD3-7. If the lineament is not a fault, then it will no longer affect consideration of seismic source potential at the Devil Canyon site. Lineament KD5-12 Lineament KD5-12 trends northeast-southwest for a distance of 14.5 miles (24 km) and approaches within 1.5 miles (2.4 km) upstream of the Devil Canyon site (Figures 8-4 and 8-5). The lineament initially was identified, in part, on SLAR imagery by Gedney and Shapiro (1975) as a linear stretch of Cheechako Creek south of the Susitna River. The lineament was extended northward across the Susitna River; this judgment was based on morphologic relationships observed on U-2 photography during this investiga- tion. North of the Susitna River, the lineament is expressed in part as a linear depression in which lie several small lakes, and in part as a l i near stream d r a i n age ( F i g u r e 8 -16 ) . T h i s depression cuts across the predominant structural grain of this area. During the field reconnaissance study, the lineament was observed at its northeast end to coincide approximately with a bedrock contact between granitic intrusive rocks on the .southeast and argillite to slate grade metamorphic rocks on the northwest. Detailed mapping is necessary to confirm this observation, which is based on reconnaissance level observations on the ground. 8 -36 No evidence of a fault, or structural control was observed where he lineament crosses the Susitna River. The northeast wall of heechako Creek, where the lineament is shown by Gedney and Shapiro (1975), was examined on the ground from a distance of approximately 1,000 feet (305 m). No evidence of fault control was observed in the granitic rocks of reported Cenozoic age (Figure 7-1); however, the resolution of this observation is limited by the distance of the observation and the access limita- imposed by the canyon walls. At the southwest end of the lineament, a shear zone (approxim- ately 200 feet (61 m) wide) was observed within the stream drain- age associated with the lineament. Whether the shear zone is related to the lineament is unknown at this stage of the invest i- Lineament KD5-12 has been classified during this investigation as being an indeterminate feature with low likelihood of recent displacement (BL)· This classification is based primarily on the shear zone at the southwestern end of the lineament and on the presence of a linear depress ion cutting across the structural grain of the area. It is also based on the absence of any evidence of recent displacement, which suggests that even if a bedrock fault is present, there doesn't appear to be recent displacement. The l i n e amen t has been des i g n ate d as a s i g n if i cant feature because it could affect consideration of the seismic source potential for the Devil Canyon site. The lineament does not affect consideration of the potential for surface rupture at either the Devil Canyon or Watana sites nor does it affect con- sideration of seismic source potential at the Watana site because it does not pass through the Devil Canyon site and because of its distance from the Watana site. 8 -37 Additional studies are considered necessary to determine if lineament KD5-12 is a fault. If it is a fault, then detailed studies will need to be considered to determi~e the related fault parameters and recency of displacement as discussed above for lineament KD3-7. If the lineament is not a fault, then it will no longer affect consideration of seismic source potential at the Devil Canyon site. Lineament KD5-43 Lineament KD5-43 trends east-west for a distance of 1.5 miles (2.4 km) and passes through the left abutment of the Devil Canyon site (Figure 8-5). The lineament is expressed morphologically as a short prominent depression, approximately 300 feet (91 m) wide, which is oriented parallel to the Susitna River. Within the depression are two small lakes with a low saddle of glacial material between them. The depression associated with the lineament was considered as a potential spillway during initial feasibility studies conducted by t he U . S . Bur e au of R e c 1 am at i o n ( U S B R ) i n 1 9 5 7 and 1 9 5 8 (U. S. Bureau of Reclamation, 1960). During the USBR study, five borings were drilled across the depression on the saddle between the two lakes. An additional boring was drilled on the southwest shore of the eastern lake and a test pit was excavated in the saddle near the northwest shore of the eastern lake during this study. In 1978, Shannon and Wilson conducted a seismic refraction tra- verse along the saddle for the U.S. Army Corps of Engineers (1979). During the 1980 feasibility study, Acres American Inc. drilled an angle boring southward from the north shore of the eastern lake. The boring was drilled beneath the lake for a 8 -38 stance of 501 feet (153m) across the axis of the depression. part of this feasibility study, Woodward-Clyde Consultants :(1980) conducted two north-south seismic refraction traverses ss the eastern lake and a northwest-southeast traverse at an to the north-south traverses and the axis of the from these studies show that a buried bedrock channel is present beneath the eastern part of the depression. The channel has a maximum depth of approximately 90 feet (27 m) and is filled with 80 feet (24m) of sand and gravel (glacial outwash) which is overlain by approximately 10 feet ( 3 m) of silt, sand, gravel, and cobbles (glacial till). borings drilled in the center of the buried valley during the USSR study encountered 11 sheared rock 11 for the 20-foot (6-m) distance the boring was drilled in rock. The boring (D-2) drilled by Acres American Inc. did not encounter evidence of a fault or shear zone beneath the depression. During this investigation, the lineament was observed to be a linear depression with glacial deposits lying between the two lakes (Figure 8-18). The canyon wall of Cheechako Creek at the east end of the lineament was examined from the air. No evidence of faulting was observed, but the airborne nature of the observa- tion and vegetation cover preclude a definitive interpretation. No evidence of displacement was observed from the air on the Susitna River canyon wall at the west end of the lineament. How- ever, access limitations and vegetation cover limit the con- fidence in this interpretation. Ground reconnaissance studies conducted along the lineament during this investigation included fracture analyses in bedrock 8 -39 on both sides of the depression and ground traverses of the saddle between the two lakes. The fracture analyses showed that fractures on both sides of the depression have similar orienta- tions. The dominant orientation is N35°W with a steep northeast to southwest dip. Ground traverses of the saddles between the two lakes showed that several linear depressions are present in the surficial glacial moraine deposits. The depressions are approximately 50 to 100 feet (30 to 61 m) wide and 10 feet (3 m) deep. The axes of these depressions are aligned parallel to the 1 ineament trend. The origin of these depressions is probably related to glaciofluvial processes; however, a fault origin cannot be precluded on the basis of available data. Considering the above information and data, the depression associ- ated with 1 ineament KD5-43 appears to be a meltwater side- channel that may be structurally controlled. According to this interpretation, the depress ion may have developed due to differential erosion along a prominent structure such as a fracture zone or bedrock fault. Subsequent glacial and/or meltwater processes served to enhance and probably deepen the depress ion, and it was 1 ater filled with sediments during a 1 ate glacial event (perhaps in late vJisconsin time). Lineament KD5-43 has been classified during this investigation as being an indeterminate feature with low likelihood of recent dis- placement (BL). This classification is based on the presence of a prominent 1 inear depression, a buried bedrock valley with a shear zone in the upper 20 feet (6 m), linear depressions in the glacial moraine deposits which fill the depression, similar fracture orientations on both sides of the depression, and the absence of a fault zane beneath the depression based on the drilling conducted in 1980. 8 -40 "'"'i>''""'"-~ ------------ lineament has been designated as a significant feature of the potential for surface rupture through the Devil The lineament does not affect consideration of seismic source potential for the Devil Canyon site because its short length precludes its being a source of a moderate to large e~rthquakes (on the basis of rupture-length versus magnitude relationships, as discussed in Section 2.4.2. The lineament does not affect consideration of seismic source potential or potential ~urface rupture through the Watana site, because of its distance from the Watana site. Additional studies are considered necessary to confirm that lineament KDS-43 is not a fault. The results of drilling con- Acres American Inc. during 1980 (boring D-2) strongly suggest that the 1 ineament is not a fault. However. because the lineament passes through the Devil Canyon site, additional data should be acquired to increase the level of confidence in this interpretation. Lineament KDS-44 Lineament KD5-44 trends north-south for a distance of 21 mi 1 es (34 km) and approaches within 0.3 miles (0.5 km) upstream of the Devil Canyon site (Figure 8-5). The lineament initially was identified south of the Susitna River as two discontinuous linea- ments on SLAR imagery by Gedney and Shapiro ( 1975). One of the lineaments followed, in part~ the northern end of Cheechako Creek whose confluence with the Susitna River is immediately upstream from the Devil Canyon site. Air photo interpret at ion conducted during this investigation identified a lineament with a similar alignment along a stream drainage whose confluence with the Susitna River is opposite that of Cheechako Creek. 8 -41 During the field investigation, it was the opinion of the Wood- ward-Clyde Consultants 1 geologists that the two 1 ineaments iden- tified by Gedney and Shapiro (1975) and the lineament identified by Woodward-Clyde Consultants should be considered as a single lineament. Therefore the field investigation and the subsequent analysis of the lineament have considered the feature as a single lineament, 21 miles (34 km) long. The lineament is expressed morphologically as a linear series of aligned stream drainage segments, small lakes, and shallow depres- sions or saddles in rolling terrain. Evidence of possible fault control is suggested by the apparent termination of a dike on the north wall of the Susitna River; a possible bedrock scarp on the south bank of the Susitna River; and discolored rock zones along Cheechako Creek. The dike described above is exposed on the north wall of the Susitna River on the east side of the drainage associated with the lineament (Figure 8-19). On the basis of the work conducted to date, the dike appears to terminate or die out at the east side of the drainage. Whether the termination is fault related~ a function of dike orientation and the orientation of the exposure, or due to the dike naturally dying out is yet to be determined. Seismic refraction studies were conducted by Shannon and Wilson in 1978 on the point bar that juts northward into the Susitna River from the west bank of Cheechako Creek. These studies included two survey lines oriented parallel to the Susitna River and at right angles to the 1 ineament. The results of the study suggest that a buried step or scarp in bedrock steps from a depth of approximately 100 feet (30m) below the point bar (on the downstream side) to a depth of 600 to 650 feet (183 to 198m) on 8 -42 ",'*'~-,~ ----------- upstream side (U.S. Army Corps of Engineers, 1979, Exhibit ). ·On the basis of these two seismic refraction lines, the buried scarp can be inferred to have a buried relief of approx- imately 500 to 550 feet ( 152 to 168 m) and its base is oriented approximately N25"W to N30°W, subparallel to the trend of linea- ment KD5-44. The southwest side of the step is up relative to the Along Cheechako Creek, zones of light colored, fractured, and highly weathered or pulverized rock were observed from the air during this investigation. The origin of these rock zones could be due to faulting. However, other origins such as weathering of a mineralized zone could also explain the observed rock zones. A long the 1 ineament only one morphologic anomaly was observed during this investigation that may be indicative of recent dis- placement if the lineament is a fault. A terrace of fluvial or glaciofluvial deposits is present along the lineament south of the Susitna River. A 1 inear shallow depression, approximately 500 feet (152m) long, is present in this terrace with an alignment parallel to that of the lineament. Examination of exposures on the margins of the terrace showed no evidence of faulting; however, the coarse-grained, cobbly nature of the deposit and access 1 imitations prevented exhaustive examination of the exposure during this reconnaissance investiga- tion. The origin of this depression is probably related to stream processes which occurred at a time when the creek in this area flowed along the surface of the terrace. However, a fault origin cannot be precluded on the basis of the data obtained to date. Lineament KD5-44 has been classified during this investigation as being an indeterminate feature with a moderate likelihood of 8 -43 recent displacement (A). This classification is based on the apparent termination of the dike on the north wall of the Susitna River, the buried bedrock scarp at the mouth of Cheechako Creek, the zones of discolored rock south of the Susitna River, and the anomalous depression in the terrace along the lineament. T h e 1 i n e am e n t h a s b e e n d e s i g n a t e d a s a s i g n if i c a n t f e at u r e because of its seismic source potential for the Devil Canyon site as we 11 as the potentia 1 for surface rupture through the site. The 1 ineament does not affect consideration of seismic source potential or potential for surface rupture at the vJatana site because of its distance from the Watana site. Add i t i on a 1 stud i e s are cons i de red n e c e s sa r y to de term i n e if lineament KDS-44 is a fault. If it is found to be a fault~ then detailed studies will need to be considered to determine the recency of displacement as well as other pertinent fault para- meters as discussed above for 1 ineament KD3-7. If the 1 ineament is found not to be a fault, then it will no longer affect con- sideration of seismic source potential or the potential for surface rupture at the Devil Canyon site. Lineament KDS-45 Lineament KDS-45 trends approximately east-west for a distance of 19.5 miles (31 km) and approaches within 0.8 mile (1.3 km) of the left abutment of the Devil Canyon site (Figures 8-4 and 8-5). The lineament was identified during this investigation as a prom- inent north-facing linear bluff along the south bank of the Susitna River (Figure 8-20). Aligned with this bluff is a small, linear stream drainage at the west end of the lineament, a linear topographic depression along the eastern portion of the 1 inea- ment, and several small lakes along the lineament. 8 -44 d and aerial reconnaissance conducted during this investiga- on showed that the lineament corresponds primarily to the front f the hills (i.e., range-front) along the south bank of the itna River (Figure 8-4) and locally is expressed as a 1 inear ugh approximately 150 feet (46 m) wide and 10 feet (3m) deep. h e 1 i n e am e n t i s u n d e r 1 a i n by a r g il 1 i t e a n d g 1 a c i a 1 t i 1 l. Water was observed flowing at a rate of approximately 3 to 5 gallons per minute (11 to 19 liters per minute) out of the till the base of the trough. No evidence of displacement was lineament has been classified during this investigation as being an Indeterminate feature with low to moderate 1 ikel ihood of recent displacement (B). This classification is based on the ominent morphologic expression of the 1 ineament and the absence of conclusive evidence which precludes fault control, or recent displacement if the feature is a fault. Lineament KD5-45 has been designated as a significant feature because of its proximity to the Devil Canyon site and because of its relatively long length. Consequently, the lineament could affect consideration of seismic source potentia 1 at the Dev i 1 Canyon site. The lineament does not affect consideration of potential surface rupture at the Devil Canyon site because of its distance from the Devil Canyon site. The lineament does not affect consideration of seismic source potential nor potential surface rupture at the Watana site because of its distance from the Watana site. A d d i t i o n a 1 s t u d i e s a r e c o n s i d ere d n e c e s s a r y t o d e t e rm i n e if lineament KD5-45 is a fault. If it is found to be a fault, then detailed studies will need to be considered to determine the fault-related parameters and recency of displacement as discussed 8 -45 above for lineament KD3-7. If the lineament is not a fault, then it will no longer affect consideration of seismic source potential and potential surface rupture at the Devil Canyon site. 8 -46 y OF GEOLOGIC CHARACTERISTICS USED TO CLASSIFY Recent Displacement Cl assificat ion 1 Indeterminent ed Quaternary displacement along a or observed fault nent morphologic expression of probable t-related features in Quaternary units or observed fault with subtle or dis- us morphologic expression of possible lated features but no suitable y cover to nccess recency of disp 1 acement line~ent with morphologic expression of ible fault-related features in Qua- units with no suitable exposure to irm or preclude recent displacement fault with no morphologic evidence of with possible faulting in bedrock, no displacement of Quaternary units. ine~~ent with no observed bedrock faulting lacking a sufficient number of outcrops quately preclude fault control. No .:.observe!d surface morphologic expression in displacement of Quaternary units. attributed to glacial or fluvial features discernible Chance alignment of unrelated features A lineament with an observed exposure of bedrock and/or Quatern~ry units which preclude existence of a fault If e' X X X X X 1. Section 8.2 describes the basis for the classification terminology. 2. Indeterminate-moderate likelihood of recent displacement. 3. Indeterminate-low-to-moderate likelihood of recent displacement. 4. Indeterminate-low likelihood of recent displacement. X Non- Significant X X X X TABLE 8-2 BOUNDARY FAULTS .l\ND CANDIDATE SIGNIFICANT FEATURES Distance' (llm) Fault (F) Clas-from Feature1 Feature2 or Linea-sifi-Fault' Length5 Dev1l Nurnber Name ment (L) cat ion3 Type (km) Canyon ldatana BOUNDARY FAULTS ADS-1 Castle Mt. R Oblique-200 105 115 Scarp, vegetational Slip ternary, possible !ro-240 em d i spl units (Detterman and Benioff R Subdue-60 50 Subducting Pacific pl Zone t ion Zone being underthrust Jlinerfcan Plate (Lahr 1980). H84-l Denali R Strike-2000 70 64 Break in slope, linear Slip trench, saddles, litho trast, continuous 1 offset Quaternary and others, 1978). CANDIDATE SIGNIFICANT FEATURES HA2-1 L BL 41 56 19 HA4-3 L 43 42 12 Break in slope, trench, tion line, sinuous offset stream, possible HA6-1 B Normal 105 34 65 HA6-5 Chulitna B Thrust 116 38 70 HA6-6 Upper B Thrust 45 40 75 Ridge, lithologic Chulitna (Hawley and Clark, HA6-6a Upper F B Thrust 16 43 70 Lithologic contrast Chulitna Clark, 19 73). Splay HA6-l3 A Thrust 27 75 45 Lithologic contrast, and Clark, 1973). HBS-1 BL 40 38 Break in slope, lithologiccl offset stream. KB6-5 A Thrust 21 70 40 Break. in slope, saddles, pas! offset of moraine (Steele anl LeCompte, 1978). KB6-66 L A 23 66 34 Break in slope, trench, veg~ t ion line, bench, litho logic contrast, discontinuous scan 1 i near streams. KC3-1 B Thrust 61 56 26 Break in slope, saddles, axil zone scarp 1 inear stre~s (Csejtey and others, 1978). KC4-l Talkeetna A Thrust 354 25 6.5 Linear streams segment, li~e flakes, vegetation line, l1tl contrast (Csejt!!Y and others KC4-23 L B 81! 28 37 Linear streams, sheared ~one KC4-26 B 12 37 Lithologic contrast, scarp, possible fault in bedrock. INUED) LTS AND CANDIDATE SIGNIFICANT FEATURES Distance• (km) Fault (F) Clas-from or Linea-sifi-Fault" Length 5 Oev1l ment (L) cat ion' Type (lcm) Canyon Watana Comments' BL 18 31 48 Break in slope, 1 inear streams. A 21 21 41 Linear streams, trench. B 51 15 35 Bre~k in slope, linear streams, trench, saddles, discontinuous scarps, possible fault observed in bedrock. B 20 31 Linear stream, scarp. A 19 11 42 Linear streams, possible stream offset, scarp. BL 13 24 Saddles, possible sheared bedrock. A 18 27 46 Linear streams, trench, possible lithologic contrast, break in slope. B Thrust 22 85 45 Vegetation contr~st, bre~k in slope (Csejtey and others, 1978). F 8 Thrust 34 61 21 Saddles, lithologic contr~st, possible offset of ridge (Kachadoori an and Moore, 1979). B 16 69 29 Saddles, lithologic contrast, vegetation line. F B 95 27 16 Break in slope, saddles, lithologic contr~st (Kachadoorian ~nd Moore, 1979). F B 18 42 4.5 Linear stream segment (Beikman, 1974). F BL 153 25 3.2 Bre~k in slope, saddle, 1 inear streams, sc~rp, 1974). (Turner and Smith, B 27 51 10.5 Break in slope, submarine scarp in Big Lake, discontinuous sc~rp, observed small she~r in bedrock, saddles. BL 50 35 0.0 Linear stream segment, trench, break in slope, vegetation line. A 5 32 8 Break in slope, ridge, trenches, saddles, discontinuous scarps, lithologic contrast. BL 13 43 11 Depression, vegetation line, scarp. BL 14 17 11 Break in slope, linear stream segment. B 17 16 23 Linear stream, lithologic contrast, oxidized and sheared zone. A 25 14 11 Break in slope, trench, saddles, vegetation line, discontinuous scarps. BL 22 34 10 Trenches, discontinuous sc~rp, line~r stream, break in slope. F A 3.2 37 0.0 Depression, oxidized zone, fault exposed in Tsusena Creek, (undated U.S. Army Corps of Engineers map). TABLE 8-2 (CONTINUED) BOUNDARY FAULTS AND CANDIDATE SIGNIFICANT FEATURES Distance' (km) Cl as-from Fault (F) Feature ' Feature ' or linea-sifi-Fault' Length' Diiv1l Number Name ment (L) cation' Type (km) Canyon II at ana KD5-l F B Thrust 25 14 23 Break in saddles, oxidized 1979). K05-2 F B Normal 5 5.6 38 Break in slope, ponds, oxidized K05-3 F B 82 5.8 23 Break in slope, litholog depression, saddles, sc zone ( Kachadoori an and KD5-9 BL 5 1.6 39 Linear stredffis, trench. KDS-12 BL 24 2.4 28 Linear depression, saddl lithologic contrast, 1 linear scarp. KD5-42 B 5 0.8 35 Break in slope, 1 inear trench. KDS-43 BL 2.4 o.o 38 Linear depression, line KOS-44 A 34 0.5 37 Linear streams, 1 i near saddles, depression in possible lithologic possible offset dike. KOS-45 B 31 1.3 41 K06-l Chulitna F B Normal 105 24 54 Break in slope, River depression scarp 1978). KD6-4 22 13 51 Lithologic TCl-3 F 27 26 65 Trench, saddles, 1 trast, linear lakes, vegetation 1 ine, 1979). Notes: 1. Appendix A explains alpha-numeric code number. 2. Feature name given where known. 3. Classification notation: R -Fault with recent displacement; A -Fault or lineament with moderate likelihood of recent displacement; B -Fault or lineament with low to moderate likelihood of recent displacement; BL-Fault or lineament with low likelihood of recent displacement. Section 8.2 describes the basis for these classifications. 4. Fault type given where known. 5. Lengths measured from 1:250,000 and 1:63,380 scale base maps as appropriate. 6. Distances measured from 1:250,000 and 1:63,380 scale base maps as appropriate. 7. Comments are based on remotely sensed data interpretation and field reconnaissance. provide information on faults. TABLE 8-3 SUMMARY OF BOUNDARY FAULTS AND SIGNIFICANT FEATURES Distance' (km) Clas-Fault (F) Length~ FeatureV 3 or Linea-s if~-• Na. Feature Name ment (L) cat 10n (km) lclatana BDUflllARY FAULTS AD 5-1 Castle Mountain F R 200 105 115 Fault Benioff Zane F R 60 50 HB4-1 Denali Fault F R 2000 70 64 W.~TANA SIGNIFICANT FEATURES KC4-1 Talkeetna Thrust A 354 25 6.5 KD3-3 Susitna Feature F B 153 25 3.2 KD3-7 L BL 50 35 o.o KD4-27 Fins Feature F A 3.2 37 D.D DEVIL CANYON SIGNIFICANT FEATURES KC5-5 20 31 KDS-2 F B 5 5.6 38 K05-3 L B 82 5.8 23 K05-9 BL 5 1.6 39 KD5-12 L Bt_ 24 2.4 28 K05-42 L B 5 0.8 35 KOS-43 L Bt_ 2.4 0.0 38 KD5-44 L A 34 0.5 37 KOS -45 8 31 1.3 41 Notes: 1. Appendix A explains alpha-numeric code number. 2. Feature locations are shown in Figures 8-2 through 8-5. 3. Feature name is given where known. 4. Classification notation: R -Fault with recent displacement; A -Fault or lineament with moderate likelihood of recent displacement; B -Fault or lineament with low to moderate likelihood of recent displacement; BL -Fault or lineament with low likelihood of recent displacement. 5. Length is that measured in Figures 8-2 through 8-5 except for the Dena! i fault length which was obtained from Richter and Matson (1971). 6. Distance is the closest approach of the surface trace of the fault or 1 i neament as measured on the base maps referred to in Note 2. 0 m 0 0 z (JJ c r --1 ):> z ul """ Ol (11 co ):> D "' n "' 3 g-, <0 r:o 0 ., G) c :0 m CXl I LOW CONFIDENCE WHETHER IT IS OR NOT DOES IT HAVE RECENT DISPLACEMENT? HIGH CONFIDENCE IT IS NOT HIGH CONFIDENCE IT DOES NOT LOW CONFIDENCE WHETHER IT DOES OR NOT HIGH CONFIDENCE IT DOES INDETERMINATE A1 INDETERMINATE A1 NON- SIGNIFICANT NOTES 1 . 2 . 3. 4. 5. Indeterminate A Moderate to high likelihood of recent displacement. Indeterminate B -Low to moderate likelihood of recent displacement. Indeterminate B L Low I ikelihood of recent displacement. Table 8-1 presents the criteria on which confidence levels are based. Section 8-2 describes the basis for the classification terminology. HIGH CONFIDENCE IT DOES NOT INDETERMINATE 82 HIGH CONFIDENCE IT IS DOES IT HAVE RECENT DISPLACEMENT? LOW CONFIDENCE WHETHER IT DOES OR NOT INDETERMINATE A1 HIGH CONFIDENCE IT DOES FIELD CLASS! FICATION OF CANDIDATE FEATURES LEGEND BOUNDARY FAULTS Faults with recent displacement SIGNIFICANT FEATURES ------Indeterminate A feature • --• --·-Indeterminate B feature NOTES 1. Explanation of significant feature classification system is presented in Section 8-2. 2. Explanation of alpha-numeric symbols is presented in Appendix A. 0 BOUNDARY FAULT AND SIGNIFICANT FEATURE MAP FOR THE SITE REGION 0 10 20 30 40 Kilometers FIGURE 8-2 LEGEND Indeterminate · A feature Indeterminate -8 feature Indeterminate -B L feature 1. Explanation of significant feature classification system is presented • in Section 8-2. Explanation of al'i)ha-numeric symbols ls presented in Appendix A. WATANA SITE SIGNIFICANT FEATURE MAP A feature B feature • • • • • • • • • · • ·Indeterminate -BL feature NOTES 1. Explanation of significant feature classification system is presented in Section 8-2. 2. Explanation of alpha-numeric symbols is presented in Appendix A. Miles DEVIL CANYON AREA GN!FICANT FEATURE M Indeterminate • A feature ---· --Indeterminate - B feature · • · • · • • · Indeterminate -B feature NOTES L 1. Explanation of significant feature classification system is presented in Section 8-2. 2. Explanation of alpha-numehc symbols is presented in Appendix A. DEVIL CANYON SITE SIGNIFICANT FEATURE MAP 0 2 Miles ~~~~ 0 2 3 Kilometers FIGURE B-5 lll Cantwell Glacier Outwash CONSULT ANTS 14658A December 1980 AERIAL VIEW OF MCKINLEY STRAND OF DENALI FAULT NEAR THE CANTWEll GLACIER FIGURE 8-6 Ill Ill Ill ,... -< c m 0 0 z en c ,... -1 )> z -1 en ~ U) m 0 "T1 G) c :::0 m 00 ~ CASTLE MOUNTAIN FAULT (AD5-1) AERIAL VIEW OF CASTLE MOUNTAIN FAULT (AD5-1) ~~~----------------------------------------------------------------------------------------------------~ '? n ,... -< c m 0 0 z en c ~ z ~ ~ .,.. Ol U1 co )> ., G') c ::c m (X) I Quaternary ( 7) Deposits' NOTE 1. Location of Talkeetna Thrust fault within the area of this photograph remains to be determined. Susitna River View is North Tertiary (?) Units OE===~==~5E0=:=====1300F~t VIEW OF TALKEETNA THRUST FAULT LOCATION ON THE SUSITNA RIVER 0)6-------------------------------------------------------------------------------------------------------------~ SUSITNA FEATURE (KD3-3) Stephan Lake ~TE The Susitna Feature (KD3-3) location lhown on this photograph is approx- ":'ate. No single morphologic expres- Sion of the feature has been observed. ,_ ~ \ AERIAL VIEW OF SUSITNA FEATURE (KD3-3) D-CLYDE CONSULTANTS 14658A December 1980 FIGURE 8-9 0 c, r < 0 m 0 0 z en c r -1 )> z -1 en .... Cll (11 (X) )> 0 "' ~ 3 tT !!l <0 (X) 0 "T1 G> NOTE SJ,Jrficial G~l Morpho1~ C 1. The location of feature KD3-7 shown ::c m on this photograph is approximate. cp No single morphologic expression AERIAL VIEW OF FEATURE KD3-7 ..... of the feature has been observed. OL---------------------------------------------------------------------------------------------------------------------~ - ... • - est VieW Oitect)dJ'I 0 1 2 Feet E:::::::::::r::::=::E=:==:=3 Approximate Scale 0-CL YDE CONSULTANTS 14658A December 1980 . . -- VIEW OF FINS FEATURE (KD4-27) AT TSUSENA CREEK FIGURE 8-11 Ill ill I: I •• DE CONSULT ANTS 14658A December 18 1980 ~~: ~::' ~ .. ... ·o .... -.... ... ............ .... ..:.:--..: "" • -= -&;> .. -· -. ·-· ., -.. AERIAL VIEW OF FEATURE KC5-5 FIGURE 8-12 0 m () 0 z en c !:i )> z -1 en "" en Ul (X) )> 0 "' (") "' 3 ~ 10 (X) 0 "'TI G) c :0 m cp ...... ' 0 50 Feet E3 1----1 ~ Approximate Scale .., . ./.; ~.-.,.,,. .. .. Southeast View VIEW OF OXIDIZED, SHEARED ZONE ALONG FEATURE KD5-2 tu~------------------------------------------------------------------------------------------------------------------------------~ FEATURE 1<.06-3 Pona~ Cr\ 1 t • • -"'" I •L"" ~l ~ ~-... ·' ~~-••• ~ .. ";.r• ••• :ll 11: 4 , .• •• .. AERIAL VIEW OF FEATURE KDS-3 CONSUL. TANTS 14658A December FIGURE S-14 .... 0 m 0 0 z en c r -1 )> z -1 en ~ ~ Ol (11 CXl )> 0 CD n CD 3 C" !!! ~ ID CXl 0 "T1 G) c :0 m cp ..... Southwest View VIEW OF FEATURE KD5-9 rn~------------------------------------------------------------------------------------------------------------------------~ . , .• 4,: ~~. ~.· .• .. 0-CLYDE CONSULTANTS 14658A December 1980 ·-· .. FEATURE KD5-12 FEATURE KD5-12 AERIAL VIEW OF FEATURE KD5-12 FIGURE 8-16 _j I DE CONSULTANTS 14658A December 1980 FEATURE KDS-42 AERIAL VIEW OF FEATURE KDS-42 FIGURE 8-17 AERIAL VIEW OF FEATURE KD5--43 LVDE CONIUL. TAN'i'S 14658A December 198 0 FIGURE 8·18 FEATURE KD5-44 \ Susitna River I FEATURE KD5-44 -(f- J AERIAL VIEW OF FEATURE KDS-44 CONSULTANTS 14658A December 1980 FIGURE 8-19 m 0 0 z -c r -t )lo z -t en ., CXl 0 .,. G) c ::::c m cp "' Sutitna River \ AERIAL VIEW OF FEATURE KD5-45 "0~--------------------------------------------------~----------------~~~--------------------------------------~ three of the reservoirs that are deeper than the proposed combined reservoir have had induced events. If the occurrence of reservoir-induced events is evaluated for a set of reservoirs for which data are readily available, the fre- quency of very deep reservoirs among reported cases of RIS can be estimated. Among the deep and very deep reservoirs, there are 28 reported cases of RIS. Of these, 10 are very deep, giving a frequency of 0.36 among reservoirs having accepted RIS. These data suggest that the deep water depth for the proposed combined reservoir should have a pronounced effect on the likeli- hood of RIS. Depending on how the population of very deep reser- voirs is assessed, the 1 ikel ihood of an ind'uced event of any size at the proposed combined reservoir ranges from 0.27 to 1.00. Thus, the potential for RIS is high for this very deep reservoir when water depth is considered as an independent parameter. Volume In addition to being among the world's deepest reservoirs, the proposed Devil Canyon-Watana reservoir will be among the world 1 s largest (in terms of volume). There are 59 reservoirs currently with volumes greater than that for the proposed reservoir. Of these, 8, or 13%, have been subject to RIS. If the occurrence of reservoir-induced events is evaluated for a set of reservoirs for which data are readily vailable, the fre- quency of very 1 arge reservoirs among reported cases of RIS can be evaluated. Among the deep, very deep, and/or very large reservoirs, there are 29 reported cases of RIS. Of these, seven are very large, giving a frequency of 0.24 among reservoirs having accepted RIS. Thus, the potential for RIS is high at the proposed very large reservoir when volume is considered as an independent parameter. 10 -12 str-ess Conditions ih!i'Oreti'ca i tnodeh ·Of RJ:S .su.g~est that Rl'!'i occ urrem;e mi!;Y be nlm'e 1 H~.e:J _y lll'ldel" J;ert.l!ll1 stres·s. Wildibo.ns tn an u(l det· others .F ;gt1re io ~'3 f'i1 d h::a't es the ClisH•l,b.Otion fo~'> tt'e s t ri ·~e-s .l'ip ($~ear). rrdtmo.l (ext~nsion<!lJ, afld thrus t 'komrwes s .ionall ty.pes o.f ;rtres$ reg,illre. The C'OJQ press1onal slre.s:s I'U rve. h app1ic>~b 1 e HI ill!l' pl'IJpos.sd Dev il Can,yon-Wah!l\1 res..e r 9eh•. The 1 i k e ~ i ho od of RI S acctlt'>rence att a. l'leep resei"IIO<i t · in il campr>es.si on a ~ sttess r egime is G.~4; ttris. est.1 111<1.tce i s ba$EQ on <1 "otnpari s on Gf t.h ~ numl<el" nf de op •r ese"'voirs 1~H~ RIS in GCffillres.sional errviro:f1ntents wtth th ose-W1 lhout RJS in ce m]>re·s-s i ~na l &11vironmel!t5. The- l l k\·el if.Q·a·a that a ·ru s e veo t of magnit~~e. (t15 ) ·~ 01' .!Jr e at et 1~i 11 O<e clr i n o cof11Pres s J;on lll e)1v tronmen t. 1s ·.iiPRro~·i mate:l' y 0, @~ (figU~"~ lCJ<-9 }. 1 n co ntrast , tne liirel1h11o.d of a magni t ut:le: l Ms,) 5 RH eVe J'1 t at a.ny fJe.e~ r eservo ir, reg!ird le ss of tn~e stre.ss regime , h O.Q15 .. itlh n fl ~ct& a ''t:omlitional pt·op- anility,'' of FN S g,fven th a t partiGular str ess env.tronmen t •. t he 1 ike l ihood of the 1a r ge'St. R'I'~ event-s 'a•l'so Vilrioes at;c !lrcflntJ tJJ tfl~ 11oc ~· ty111! iiJre\'at.en.t at. a r&s-enetr. !'igu -r:e lP-10 is a P<lOt of 4 CC.ll rrei'!ce of tn·e J.arge'S :t R1S events f o:r sea 111ien:t::a,ry, 'iyneous., al)<l Jfleta mor pll~c geol q.gl•t'; i!Ovtronme l}ts. i h e. l<;!'11eO.y.s g ep )·og,,x cun1e., witt:l a 1 ike:Hno.od Glf 0.1'2 for o;:;o,lr l"ence ot. at l ea·st one RfS, evet1t ; 'i·s ili'JD!icable t e ttre l,)t~posed ue.vi\ C:any.cm -w -atana t"e;s ervo1r .. T~e 1 ikel'iih ofl!l thet a IUS event of m ~gni tiJ .t\e (l~~l 5 ell" griil!ter \'1 '~ r I O C ~\.lf' ;·s ~j;JIWDI\ imatel y 0 ,05 , ]Iii -lJ 10.3.2 Evaluation of Potential Occurrence Likelihood of Occurrence Twenty-seven percent of all very deep reservoirs have had RIS. Thus, the 1 ikel i hood that any very deep reservoir wi 11 ex peri- ence RIS is 0.27. However, the tectonic and geologic conditions at any specific reservoir may be more or less conducive to RIS occurrence. Models have been developed by Baecher and Keeney in Packer and others (1979) to estimate the hkel ihood of RIS at a reservoir, characterized by its depth, volume, faulting, geology, and stress regime. Two models used here treat depth and volume as dependent vari- ables, while the other variables are assumed to be independent. In one model, depth and volume are treated as discrete variables (i.e., deep, very deep, large, very large), and in the other model, depth and volume are treated as continuously dependent variables (thus a specific depth/volume combination, such as 183m/10,000x106m3 is assigned). This approach was taken because (chi-squared (x2)) tests of independence of these variables suggest that water depth and volume may have a weak dependency while other combinations of attributes are not dependent. The relationship of water depth to volume is treated differently in the two models because the degree of dependence between the two variables apparently differs depending on how the variables are considered. In these models, conditional likelihoods are assigned to each variable on the basis of occurrence of RIS at reservoirs with that attribute. For example, the likelihood of RIS at a very deep reservoir in a compressional stress regime is 0.50. These attribute likelihoods are then combined using established 10 -14 ~tM1~tl~c\l pruceaures to Ohlllllt • :er:rpn•f ~ I Uu:lfhood of Rl ! r!J)r ~lit 04rt.lc:ul!r charec.ter 1" I tt af ll>e resef'VOll' O't lnhere$1 for ll'le comlltned !lev11 G~I\)'On-Wat•n .. ~~~Ef'~Oir. ttoe IT~el tnOOd of QCC IIrt:l!nCe elf 3 1\IS even t nt 411\1 n:~ rmge.s frM n Z9 10 0.9 The nat.cstical relat l•mtlllp ; Y'>ell to oo ta1n nds lilt I ltiC'IId .:.NO <ll !t ~s setl in Pac er Jl'ld ot oars (1!)7()), fhe re l at i'i e l ~ lllyh like li hood reflects lhe ezlrlllli! lleptll and volun~.a of ne f'Uer1olr Onl.)' 11lfiE ctner re•ervclf'\ I•Qr\o~tlde OU Of a ~p~ \5T len Q! )pOI"'J.I"ste:IJ ll,Q()O tire 'H!f'V dEep Gild ¥E' t l <1~ge Mq CJOI v Dfli: of tltese, "ure~ Wh lLh ho\ ti:ld RIS., 1~ both qaeper and lar ger Be&.aus e llll! OP~ II Canyon-Watarra !'e.er~Cifl 1 ~ '!110!19 ~nf lle.ep~sl of til~ \ll!ry ueiO t.ttego,.y, l.he llkl'ltlnJW 11 f iHS 1S ven hiqh us in~ \Ill" c011t tnunus depend~ce miall l!l •ntl •ljj•<Dh~t lot~er ~s II!Q Utf. "litfl!.tt. Llepenclence nm de I rill! tiiUd~l· fm1! ~Inn Ln uu tkel t hoods are denved "re prrt lm- tnary ~ -.Ensitlvit:r '"li V<t l• i ndic.ari!d that ~he. lll.etlhall'h al"ll. very se•tsl tliiE ~o &:11~1'11:11!\ th data c:las~t ·l t.~tfllll part •tu- IBr ly among t.hos~ Jeep r!s~rv~1r~ ~nor a~~ dCtuo t eO casos nf ~rs (Pac._cr 11'111 Otfler~. l!H9 ) Thus . the specific llkPI lhoods obnlnEd f rom tiles!! nlodel s 111ur.t be usea wnh caut 1n n The depth an !-\follrn~ ll lhl! prOtlosed reservo1t ts alllUn9 tnt. i'?tt 11'1~$ 1110s t I 1 al.l' t.O be subJI!C:t ta 1\15, so tilt' 1 tl("llt•ooo of J!I:G ttrrente O! Rl5 llntlulltnq -·croeartltQJl altesj Ill til• lle'ttl t:.;n_)(IO-Wl't.1ne re~ervo1r •s cons I de~" t.e oe I1 1C1h . Hulmum ,.he li aservtr tl'\ l\r'e bE]lEVI!O \o 11 1 ocrltlrbll t ion on the (lruent H.f'\155 reg fme t.ha t tan lf ·~9" 1n ~·w l.hqu~e by me~n\ ur 11 Sllln1 1 ) I I • \~ incremental increase in stress or an increase in pore pressure as discussed in Section 10.2. Thus, the reservoir triggers strain release commensurate with that which a region can sustain within the present stress regime. Careful study and evaluation of the maximum credible earthquake for a region provides the upper bound for the size earthquake that a reservoir can trigger. That is, a reservoir cannot trigger an event larger than the maximum credible earthquake because it is a small perturbation added to the existing stress regime, not a major source of stress which would generate earthquakes independent of the existing stress regime. An RIS event typically will be of lower magnitude than the maximum credible earthquake (e.g., many of the maximum RIS events are microearthquakes that are several orders of magnitude smaller than the maximum credible earthquake for a region). Because of the limited influence of the reservoir on the existing stress regime, the reservoir is unlikely to trigger the maximum earth- quake (unless stored stress is nearly sufficient for such a failure), even though it may trigger failure along a fault. Furthermore, a reservoir may trigger an earthquake before the tectonic stress is built up to maximum event levels that would trigger a large 11 naturally occurring 11 earthquake. In other words, by reducing the strength of tectonically-stressed mater- ials, the reservoir may trigger an event that is smaller and that occurs earlier than a naturally occurring event. The reservoir may also have an impact on the location of the 11 naturally occurring 11 earthquake. The reservoir may trigger the 11 naturally occurring 11 event on a structure closer to (as well as within) the reservoir than would otherwise occur. 10 -16 RIS events have exceeded the earthquake that had been used design in several instances (e.g., Koyna). Review of these cases suggests that thorough geologic and seismologic studies of faults within the hydrologic regime of the reservoir would have ulted in a maximum credible earthquake at least as large as the RIS events occurring in the vicinity of the reservoir (Packer and others, 1979). With these data, an appropriate design earthquake and ground motions can be selected. Location As discussed in Section 10.2.2, reservoir-induced seismicity occurs in the region under the influence of the reservoir's hydrologic regime and stress. Because of the configuration of the Devil Canyon-Watana reservoir, it can be modeled as a half- pipe at the top of a half-space as discussed by Withers (1977). A qualitative review of this model indicates that increases in normal stress are essentially localized beneath the reservoir. Shear stresses have their greatest concentration beneath the deepest part of the reservoir; however, their effects can extend to depths and distances up to three times the width of the reservoir (as measured from the center of the reservoir). The typical width of the proposed Devil Canyon-Watana reservoir is 0. 6 to 1. 9 mi 1 es (1 to 3 km) with a sect ion at Watana Creek that will have a width of approximately 8 miles (13 km). Thus, the maximum width of the combined reservoir will be 8 miles (13 km) at one location. For the purposes of this investigation, we have assumed that the average width of the combined reservoir is somewhat less than the maximum local width and larger than the typical width. The average width of the combined reservoir is assumed to be 6 miles (10 km). Thus, the hydrologic effect of the combined reservoir can be inferred to extend vertically 10 -17 and horizontally a maximum distance of approximately 19 mil (30 km). This volume, which includes the reservoir and a envelope 19 miles (30 km) in radius around the reservoir ver tically and horizontally, represents the maximum area of hydro- logic influence of the reservoir. It is inferred that reservoir~ induced events would occur within this space about the reservoir. Temporal Relationships As discussed in Section 10.2.1, most ~reservoir-induced events occur within the first five years of impoundment. This relation- ship is applicable primarily to reservoir-induced microearth- quakes. For larger events of magnitude greater than 5 (of which there have been 10), 30% have occurred between 5 and 10 years after impoundment, including the Koyna event of magnitude (Ms) 6.3. Consequently, a potentially damaging event (mag- nitude (Ms) greater than 5) has a relatively high likelihood of occurring up to 10 years after impoundment of the reservoir. 10.4-Effect of RISon Earthquake Occurrence Likelihood The likelihood of RIS occurrence at the proposed Devil Canyon-Watana reservoir can be combined with the frequency-magnitude relationship for naturally occurring seismicity in the Devil Canyon-Watana area to assess the combined likelihood of earthquake occurrence. However, this approach generally assumes that, for earthquakes of magnitude (Ms) > 5 to occur, faults with recent displacement (capable of generating an earthquake of this magnitude) are present within the hydrologic regime of the reservoir (as discussed in Section 10.2.2). To date this investigation has not identified any faults with recent displacement within the hydrologic regime of the Devil Canyon-Watana reservoir, although the results are preliminary. Consequently, it is considered 10 -18 re to assess the 1 ikel ihood of RIS events of magnitude (Ms) > 5 additional data are obtained on the recency of faulting in the logic regime of the reservoir during the 1981 field season (discus- n Section 14). Implications of RIS for Method of Reservoir Filling occurrence of RIS events has most often been carrel ated with of a reservoir, especially with irregular filling histories or rapid reservoir refill following major draw- downs (Packer and others, 1979). The precise relationship between irregularities in the filling cycle and the occurrence of RIS events is not well-documented in most cases. Furthermore, no cantrall ed experiments have been performed at reservoirs to vary filling rates and examine the effect on seismicity. However, detailed information is available on the correlation between seismicity and filling rates for at least one reservoir--Nurek, U.S.S.R. Although impoundment at Nurek began in 1968, the first signifi- cant impoundment (to 328 feet ( 100 m)) took place between 1 ate August and early November 1972. A step was made in the filling curve late in September; following this step, seismicity increased. Upon completion of the first stage filling cycle. seismicity reached a peak with maximum magnitudes (Ms) of 4.6 and 4.3. Seismicity between November 1972 and June 1976 broadly paralleled changes in water level (Simpson and Negmatullaeu, 1978). On the basis of this experience, it was recommended that second- stage filling resulting in a water depth of 656 feet (200m), be accomplished by a smooth filling cycle with no abrupt slowdowns in filling rate. Seismicity remained low during this filling until a minor but rapid fluctuation in filling rate occurred in August 10 -19 1976. Following this fluctuation, there was a pronounced increase in seismicity, along with the occurrence of the largest event reported to that time, a magnitude (Ms) 4.1 earthquake. It has been implied that the increase in seismicity during this second filling cycle may have been directly related to the sudden change in rate of filling (Simpson and Negmatullaev, 1978; Keith and others, 1979). From this experience at Nurek, and from consideration of the correlations between filling curves and seismicity for other cases of RIS, it appears that sudden changes in water level and sudden deviations in rate of water level change are common triggers of induced seismicity. A controlled, smooth filling curve, with no sudden changes in filling rate, should be 1 ess 1 ikely to be accompanied by induced seismicity than rapid, highly fluctuating fillinq rates. 10.4.2 Potential for Landslides Resulti Induced Seismicity from Reservoir- Any assessment of the potential landslides resulting from RIS should be considered within the context of the overall potential for landslides and rockfalls in the reservoir area. That is, the potential for landslides which can be triggered by impoundment of the reservoir by natural processes (such as freeze-thaw conditions) as well as by RIS should be considered. Within this context, we have considered the potential for landslides triggered by RIS by making a preliminary assessment of whether in-situ conditions suitable for landslides exist in a proposed reservoir area, and whether earthquakes will release enough energy to trigger 1 and- slides. During this investigation, a very preliminary assessment of land- slide potential has been made from remotely sensed data interpreta- tion, review of previous studies conducted for the project, and 10 -20 ~~~ and gt ilUf'ld i'<'C.Un n>ll>S,s a i\C f! st,\J d i@§. Ol'l t l\~1\ 1.\as l s, it tB ""IYd.etl th~ o t~ter:tt;1 al e-~1!it.s. fot• 1arid1!1 i·J!!·e-; t,o tJ G~a r-i n t hl? \!'Moir area . 1~S av el'l t o~~IJI'r in 9 ,Wf'th in 'l.~e \i y d rOl•JQi ~: negillie Q f t he r ;;s e r • ·c ould i1rlg ~!H' a l &n ds l i da l'f t11e averlt OGMJI'I'ed r.lase e11ougfi J 1 ~olen ,H al o;lt~e ur e a a:n tl if H re le~s(ld s uH i ,c ~en t ~n ef\g y to , ,ypr a ~l 'icte. 1\t t h h po int tn tlw ijMe s Hgat iot~., t he loc:a tion s t,e cf an ~I S ev,n t 'it ~l n th e hrd r q ~ogi t r ~9 i m 1 of t he ]J ted re!(Brv o:il' x;~nnet be es ti ma•t,-ell l~i t.h ~t.~if.~ci~nt p t'~c1s iol l to j.rle a filea )l jn~fUI as s e ~S:rrten t of Wi'l e;~~ l\1 Hie Nfs tU Vo ir a 1and - ~C!)ll ld oc,cur an d ha w Ja.r g., M e'lrtnt1 1Jak.t! Wc11Jltl be: Mte!lsd ry t o Y.,~l" ~ l!lnilslide , Howw er , t ha confi .~u l"i:rtio,n Qf-til ~; Sus-1t na r v a1i~y h su r.h t~~t t l1 e-r e a !I J:fe~r s t o oe ~i H..'\e l1~e ~'lhoo d a large h nd s Hd e (sLi c:h a,§ oc oU vrell a t Va·Jo nt , t telY ) 11QI.Jld , in ttw ptopo~ed r.~s e J•vo ir auf·1 n\l .;n IW; eve nt. HJ -~ CASES OF RESERVOIR-INDUCED SEISMICITY Lake i'lont !cello Pieve di Cadore Porto Co 1 OOtb ia Shara~athi Volta Grande Sagar Lake llarragamba, Lake Burragorang Xinfengj 1 ang Country Ghana Spain Yugoshv1a Mew Zeal and Australia USA Brazil Spain Spain USA S11itzer land USA Spain Soli tzer 1 anrl Australia USA India Yugoslavia France South Africa USA Zzmbia USA Japan I !milia/Rhodesia Greece Turkey USA Ind1 a Ind 1 a Greece Japan Spain Spain Ind1 a Pak !stan Canada Greece Canada France India USSR USA Algeria USA Ind 1 a Italy Italy Brazil USA USA USA Austria Iran Indin USA India Austral! a India Italy Brazil Fr11nce Australia Chi nil Data source: Packer and others (1979). Classification of RIS Accepted, macro Accepted, micro AcceptEd, micro Accepted, ~Z~<~Cro 4lld micro Accepted, macro and micro Mot R!S Questionable Accepted. macro Accepted, macro Accepted, micro (macro1) Accepted, lll1cro Accepted, macro Not R!S Accepted, l!llcro Accepted, macro Accepted, micro Questionable Accepted, micro Accepted, macro and micro Accepted, micro Accepted, macro and micro Accepted, macro Accepted, macro and n~icro Accepted, ro1cro Accepted, macro and micro Accepted, macro Accepted, micro Accepted, macro Questionable Accepted, macro and micro Accepted, mocro and rn1cro Accepted, macro and micro Questionable Questionable Questionable Not RIS Accepted, macro and micro Accepted, IIIOCro Not RIS Accepted, macro Al:cepted, micro Accepted, mocro and micro Accepted, mncro Accepted, micro Accepted, micro Questionable Accepted, macro and micro Accepted, mncro and micro Accepted., macro Not RIS l«<t RIS Not RIS Accepted, micro Questionable Quest1on~~ble Accepted, micro Questionable Accepted, macro and micro Questionable Accepted, micro Al:cepted, macro Accepted, macro Questionable Accepted, mocro and micro M&gn itude of Largest RIS Event' Intensity V less than 2 Less than 3 5 (1) 3.5 Approx.. 4 4.1 4. 7 4.3 (1) Less than 3 5.2 less than 3 5 (1) 2.8 Less than 3 Intensity V Less 5.0 4 or 3.2 Less 6.25 4.6 less 4.9 6.5 6.3 4.9 4.1 5.75 than 2 less (1) than 3 than 3 Intensity VII Less than 1 4.5 5.7 less than 3 3. 7 ( 7) 4.4 Intensity V Intensity VI to VII less than 2 4. 7 less than 3 3.5 Less than 3 less thnn 4 4.4 5.4 Nwnbers correspond to numbers in Figure 10·1; Klnarsan1 and Sharavathi are unplatted because of insufficient datil. llllere only one nl!!lle is gi~en, either the reservoir nane Is the same as the dCill name or only the d!:m neme is knOtlll. A dash indicates the m~gnt1ude was not obtained. Intensities are given in Modified Merca111 Sc~le. TABLE 10-2 RESERVOIR-INDUCED SEISMIC EVENTS WITH MAXIMUM MAGNITUDE OF 5 OR Dam Reservoir Magnitude Koyna Shivaji Sagar Lake 6.5 Kariba Lake Kariba 6.25 Kremasta Lake Kremasta 6.3 Xi nfengj i ang Xinfengjiang 6.0 Marathon Lake Marathon 5.75 Oroville Oroville Reservoir 5.7 Coyote Valley Lake Mendocino 5. 3 Benmore Lake Benmore 5.0 Eucembene Lake Eucembene 5.0 Hoover Lake Mead 5.0 Notes: 1. Data Source: Packer and others (1979). Active Fault Present 2 Yes Not Yes Yes Yes 3 3 Yes 3 Yes 2. Active faults are those defined as having displacement in the present tectonic stress regime. 3. Determination is based on field reconnaissance studies. 4. The presence of an active fault has not been obtained but is considered probable because of the tectonic setting. 240 220 200 180 160 140 o•o 0 120 100 80 60 )2. "·· .. l?.o : ... 1 Eli3 6 19 31 32 645 655 ~.44 51~ Watana ;-:: .. :30 ~ - .c;=,l62 l ::;]L .· Combined 25 40 '=8 @e24 Approximately 11,000 reservoirs without reported RIS not plotted 20 r;:::::ll12 liBJ}-,7 100 1,000 ~59 ~ 10,000 100,000 500,000 Reservoir Capacity in 106 m3 (logarithmic scale) LEGEND Deep and/or very large reservoir Accepted case of A IS, maximum magnitude~ 5 Accepted case of RIS, maximum magnitude 3-5 Accepted case of R IS, maximum magnitude S 3 Questionable case of R IS Not RIS CON~UL TANTS 14658A December 1980 Note: The following reservoirs were not plotted because of insufficient data: Kinarsanl, Sharavathi. •41 -Nurok (USSR) depth is in excess of 285 m. PLOT OF WATER DEPTH AND VOLUME FOR WORLDWIDE RESERVOIRS AND REPORTED CASES OF RIS FIGURE 10-1 EFFECTIVE STRESS Slippage occurs when the Mohr circle touches sliding envelope given by: T "' t 0 + )J rr is the coefficient of friction of the rock.. In a fluid pressure P, the Jo!ohr circle is moved to the left to Circle 2 defines a 1E where: STRIKE-SLIP FAULT (Jl\ stress regirre, represented by strike-slip faulting. the (a1} and the '""llest stress (a 3} ore horizontal. a vertical load increases o1 and o3 by P/3 {in Poisson's ratio y • 0.25) and shifts the Hohr circle by P/3 to pos1tibn 2. When fluid is introduced into the Jobhr circle rrcves to the left by the 11r.ount of the P to pos1t1on 3. The f1nal l'l:lhr c1rcle (3} 1s of (1), but is offset tow11rds after Gough (in press) and Withers (1977). CONSULTANTS 1465BA December 1980 ® ® T NORMAL (DIP-SLIP) FAULT In an extensional stress regime, represented by norrm.1 faulting, the largest stress {cr 1) 1s vertie!l ~:~nd the sma11est stress (a 3) is horizontal. Application of a vertical load increl!ses o-1 by P and o 3 by P/3 (in rraterhl with Poisson's ratio r • 0.25). The fltlhr circle nnve.s to position 2, and has a larger r~:~dius than at position 1. When fluid is introduced into the fault~ l'bhr circle 2 nnves to the left by the arrount of f1uid pressl.ll"e P to position 3. Relative to the preloading condition (1), the fin11l condition (3) is less stable, 11nd subject to failure. THRUST FAULT In a co~Jl)ressional stress regime, represented by thrust faulting, the smallest stress (o3) is vertical and the hrgest stress (o1) 1s horizont11l. Applic11tion of 11 vertical load increases a3 by P and a 1 by P/3 (1n 1113ter1a1 of Poisson's rat1o r • 0.25}. The M:lhr circle ll'l)ves to position 2, h11s 11 smaller redius th11n 11t position 1, 11nd represents 11 oore st11ble condition relative to the 1n1tilll condition. When fluid is introduced into t~ f11ult, Mohr circle 2 moves to the left by the ,zmount of fluid pressure p to position 3. This condition is also rrore stable thll.n the 1nithl condition. In a con'f?ression~~l stress regirre, loading the reservoir may lead to st11bi1ization of the area. DIAGRAMS SHOWING EFFECTIVE STRESS RELATIONSHIPS FIGURE 10-2 Bajina Basta Camarillas Mula Coyote Valley (Mendocino) Fairfield (Monticello) Hendrik Verwoerd Kamatusa Oued Fodda Pi astra Porto Colombia Volta Gran de Kastraki Akosombo Almendra Sen more Emosson Grancarevo Jocassee Kariba Kebiln Krem<lsta Manicouagan 3 Monteynard Nurek Piel/e di Csldore ShastCl Talbingo Vajont Xinhmgji1mg ( Qmelles Contra Eucumbene Hoover Kurob<! Schl'*is Blmwring, Koyna, Vough3ns LEGEND 15 Years from Start of Impoundment to First Suspected RIS Event 20. Accepted R IS cases that are neither deep, very deep, nor very large Accepted R IS cases that are deep, very deep, and/or very large 25 PlOT OF TIME BETWEEN IMPOUNDMENT AND Fl RST SUSPECTED FUS !EVENT DE CONSUL TAN 1465BA Daceml:ler 1900 FIGURE 10-J 30 25 20 "' ... '(5 (: (!) "' (!) a: 15 ..... 0 .... (!) .D E ::::l z 10 5 0 ~ . ' 5 LEGEND Fmirfield (Monticello) Hendrik Verwoerd Kamafusa Mula Oued Fodda Pi astra Porto Colombia Volta Grande Akosombo Manicouagan 3 Almendra Monteynard Nurek Grancarevo Pieve di Cadore Keban Shasta Kremasta Kastraki reomoce Kurobe Canelles Schlegeis Contra Tal bingo Eucumbene Vajont ( Vouglans, Xintengjiang {Camarillas Coyote Valley (Mendocino) G randval { Blowering Jocassee Hoover Kariba 10 15 Years from Start of Impoundment to Largest Suspected R IS Event 20 25 Accepted RIS cases that are neither deep, very deep, nor very large Accepted R IS cases that are deep, very deep, and/or very large PLOT OF TIME BETWEEN IMPOUNDMENT AND LARGEST SUSPECTED RIS EVENT D-CL YDE CONSULTANTS 14658A December 1980 FIGURE 10-4 ® @ G) ® ® ® @ ~ @ IE) 2 4 5 6 7 B Magnitude of Largest R IS Event LEGEND ® Deep reservoir in extensional or shear regime 8 Deep reservoir in compressional regime DE CONSULTANTS 1435SA December 1960 PlOT OF MAGNITUDE OF lARGEST RIS EVENT VERSUS TIME AFTER IMPOUNDMENT !FOR ACCEPTED RDS AT DEEIP, VERY DEEP, AND/OR VERY lARGE RESERVOIRS FIGURE 10-5 5 4 3 ® (1l 2 ll> 0 ® ® ® ® @ €! G) G (II @ 11! (II ll> • • £!> "' 0~--------T---~--~~-------r--------~e--~e------~ 2 3 4 5 Magnitude of Largest A IS Event NOTE 1. The Oroville earthquake of magnitude (ML) 5.7, which occurred 7.6 years after the start of impoundment, is not plotted. 6 7 PLOT OF MAGNITUDE OF LARGEST RIS EVENT VERSUS TIME TO FIRST RIS EVENT AT DEEP, VERY DEEP, AND/OR VERY LARGE RESERVOIRS ANTS 14668A December 1980 FIGURE 10-6 ~ 0::: ..... 0 "' u c "' ,_ ,_ :::J u u 0 '+- 0 > .t:: .0 "' .0 e CL 0.25 0.20 0.15 0.10 0.05 2 3 4 5 6 7 Magnitude of Largest R IS Event PROBABILITY OF RIS OCCURENCE WITH MAXIMUM MAGNITUDE ;.M FOR DEEP VERY DEEP, AND/OR VERY lARGE RESERVOIRS CONSULT ANTS 14658A December 1980 FIGURE 10-7 2 3 4 5 6 7 Magnitude of Largest R IS Event LEGEND Deep, very deep, and/or very large reservoirs with first R IS event more than one year after impoundment ------Deep, very deep, and/or very large reservoirs with first RIS event more than two years after impoundment DE CONSULTANTS 1465BA December 1980 PLOT OF VARIATION OF RIS PROBABILITY WITH DELAY TO fiRST EVENT FIGURE 10-8 0.25 VJ cr: -0.20 0 "' t.l c "' .... ::J t.l t.l 0 -0.15 0 > .... :0 "' .a 0 a: 0.10 0.05 2 LEGEND CONSULTANTS 3 -- 4 5 Magnitude of Largest RIS Event .......... 6 ...... , \ \ I Deep, very deep, and/or very large reservoirs in thrust (compressive) stress regime Deep, very deep, and/or very large reservoirs in normal (extensional) stress reqime Deep, very deep, and;or very large reservoirs in strike-slip (shear) stress regime 7 PLOT OF VARIATION OF RIS PROBABILITY WITH DIFFERENT STRESS REGIMES FOR DEEP,· VERY DEEP, AND/OR VERY LARGE RESERVOIRS FIGURE 10-9 0.25 0.20 0.15 0.10 0.05 2 3 4 5 6 7 Magnitude of Largest R IS Event LEGEND Deep, very deep, and/or very large reservoirs with sedimentary geology -------Deep, very deep, and/Dr very large reservoirs with igneous geology Deep, very deep, and/or very large reservoirs with metamorphic geology PLOT OF VARIATION OF RIS f'ROBABIUTY WITH DIFFERENT GEOLOGIC SETTINGS FOR DEEP, VERY DEEP, AND/OR VERY LARGE RESERVOIRS DE CONSUL TANYS 1~A DKembar 1900 FIGURE 10.10 PRELIMINARY MAXIMUM CREDIBLE EARTH approach to estimating the maximum credible earthquakes in a region, thereby to establishing a basis for estimating the ground motion at ecific site, is based on the premise that significant earthquake ivity is associated with faults with recent displacement. The evalu- ion of the maximum credible earthquake, which may be associated with a en fault, is closely related to the geologic and seismologic setting fault activity in the region of the site. Therefore, it is necessary identify the characteristics of the faults with recent displacement order to assess their seismic source potential. For this study, e only faults accepted as having had recent displacement within or acent to the site region are the Denali fault and the Castle Mountain ault. The Benioff zone passes at depth beneath the site and is a 1 so idered to be a potential seismic source. this investigation, selection of maximum credible earthquakes for lts with recent displacement and the Benioff zone is considered pre- Consequently, the maximum earthquakes estimated for these aults and the Benioff zone are designated as preliminary maximum cred- ible earthquakes (PCMEs) and are subject to revision during addi- studies. Because the method of estimating these PCMEs is conser- ative (as discussed below), any revisions is expected to result in a aximum credible earthquake of lower or equal magnitude than that estimated to date from available data. The results of the investigation to date indicate that no faults within the Talkeetna Terrain have had recent displacement. Consequently, it is inappropriate at present to consider formally PMCEs for faults within the Talkeetna Terrain. The methods used to estimate PMCEs are briefly summarized below and the fault rupture length methodology used for the Denali and Castle Mountain faults is discussed in more detail in Appendix E. It is recognized that these methods may lead to excessively 11 - 1 large earthquakes being hypothesized as PMCEs. However, for purposes evaluating project feasibility, the methods are considered to provide reasonably conservative estimate of PMCEs for a given source. 11.1 -Distant Sources outside the Talkeetna Terrain 11.1.1 -Sources Outside the Talkeetna Terrain The PMCEs for sources outside the Talkeetna Terrain, such as Aleutian Trench or the Fairweather fault, are not of significance to the Project because of the distance of these faults from Project and because of the presence of seismic sources such as Denal i-Totschunda fault system and Benioff zone which are cl to the Project. Even if it is assumed that a magnitude (Ms) event could occur on a known seismic source outside the Talkeetna Terrain, the resultant ground motions would be significantly less than those for the Denali fault. Consequently, PMCEs associated with seismic sources outside of Talkeetna Terrain have not been considered further for this investigation. 11.1.2 -Talkeetna Terrain Bound Sources Estimates of PMCEs have been made for three of the boundaries of the Talkeetna Terrain. These boundary sources are the Denali- Totschunda fault system to the north and east, the Castle Mountain fault to the south, and the Benioff zone at depth. Because no single brittle deformation feature forms the boundary to the west (as discussed in Sect ion 5), no PMCE has been estimated for that boundary. The PMCE for the Denali-Totschunda fault system is estimated to be a magnitude (Ms) 8.5 event. This estimate is based on the 11 - 2 assumptions that: as much as one third of the 1,250-mile (2,000- km) length of the fault system could undergo displacement during a single event (as discussed in Appendix E.2) and, the style of movement on the Denali fault during the earthquake would be one of strike-slip displacement. The PMCE for the Castle Mountain fault is estimated to be a magnitude ( Ms) 7. 4 event. This estimate is based on the assump- tions that: the entire observed length of the fault system could undergo displacement during a single event; and, movement on the fault during the earthquake would be one of oblique-reverse s l i p. The PMCE for the Benioff zone is estimated to be a magnitude (Ms) 8.5 event. This estimate is based on the assumptions that: the 1964 Prince William event of magnitude (Ms) 8.4 represents approximately the largest event that can occur on the Benioff zone; and, a magnitude (Ms) 8.5 accommodates uncertainties in magnitude (Ms) for this size event. The PMCE for the Denali-Totschunda fault system, should it occur at the closest approach of the fault system to the Project sites would occur at least 40 miles (64 km) from the sites. The PMCEs for the Castle Mountain fault and the Benioff zone would occur at least 65 miles (105 km) and 34 miles (50 km) from the sites, respectively. These are the closest seismic sources considered to have the potential of generating a PMCE of greater than magnitude ( Ms) 5 . 11 - 3 11.2 -Effect of Reservoir-Induced Seismicit on the Preliminar Credible Earthquakes The hydrologic effects of the impounded reservoirs are postulated influence an elliptical shaped area that extends 19 miles (30 km) the perimeter of the proposed Watana-Devil Canyon reservoir as discus in Sect ion 10. The reservoir will not affect consideration of along faults outside the hydrologic regime of the reservoir, includi the Denali and the Castle Mountain faults and the Benioff zone. For faults and possible faults within the hydrologic regime of reservoir, the influence of a reservoir is believed to be 1 imited that of a triggering mechanism (as discussed in Section 10). For mode ate to large earthquakes (magnitude (Msl > 5), reservoirs with acce cases of RIS are not known to have triggered events 1 arger than cou have occurred naturally along faults with recent displacement. fore, the effect of RIS on faults within t~e hydrologic regime o the proposed Watana-Devil Canyon reservoir cannot be adequately until additional geologic data are obtained on the significant features (discussed in Section 8-5). If subsequent studies show one or more of the significant features is fault with recent displacement (with a defined recurrence interval and displacement), a maximum credible earthquake can be estimated for that fault. The effect of RIS is expected to be 1 imited to decreasing the recurrence interval of such an earthquake. The location of the earthquake is also expected to be constrained to the section of fault lying vdthin the hydrologic influence of the reservoir. RIS would not be expected to increase the size of a maximum credible earth- quake estimated for a fault with recent displacement. 11 - 4 PRELIMINARY GROUND MOTION STUDIES objective of the studies described here is to develop preliminary ates of the characteristics of ground shaking at the Watana and 1 Canyon sites resulting from preliminary maximum credible earth- s on the known faults with recent displacement in the site region. ground-motion characteristics addressed in this section include peak tal ground acceleration~ response spectra, and duration of strong shaking. known faults with recent displacement are the boundary faults of the na Terrain: the Denali fault, located north of the sites; the Mountain fault, located south of the sites; and the Benioff zone underlies the site region at depth. The closest distances of faults from each site and the preliminary maximum credible earth- e magnitudes for the faults are the following. Preliminary Closest Distance of Fault Maximum Credible to Site ( km) n itude Watana Devil c n 8.5 70 64 Mountain 7.4 105 115 8.5 50 60 ents or faults in the Talkeetna Terrain are not addressed in these because these features are not currently known to have been ect to recent displacement. If the future seismic geologic studies ntify any of these features to be faults with recent displacement, ground motions associated w.ith such faults should be evaluated. 12 - 1 12.1 -Methodology for Estimating Earthquake Ground Motions 12 .1. 1 -_P...:..__G_r_o_u_n_d_Ac_c_e_l_e_r_a_t_i _on_ Woodward-Clyde Consultants (1978), Idriss (1978), Crouse and (1980), and ongoing studies at Woodward-Clyde Consultants indi that ground motions from Benioff zone (subduction zone) earthqu have different characteristics than ground motions from focus crustal earthquakes. The estimates of peak acceleration Benioff zone earthquakes were based primarily on the attenuat relationship developed from statistical analysis of recorded str motion data from worldwide historic Benioff zone earthquake these analyses were conducted primarily during a previous analysis of ground motions in Alaska (~Joodward-Clyde Consult 1978). The data used in that study consisted of strong mot recordings from subduct ion zone earthquakes in Japan and America, as very few such data are available from Alaska. the present study, the limited data from Alaska were examined found to be reasonably consistent with the results of analysis. For shallow crustal earthquakes, peak accelerations were selected by examining recorded rock-site data for such earthquakes and published attenuation relationships and ongoing ground-motio studies of Woodward-Clyde Consultants. The applicable data examined are primarily from California, with a few data points from Alaska. The limited Alaskan data were found to be reasonably consistent with the other data used. The published attenuation relationships examined in estimating peak accelerations included Schnabel and Seed (1973), Seed and others (1976), Idriss (1978), and Seed (1980). Peak horizontal ground acceleration values were estimated for the preliminary maximum credible earthquake on each of the faults. The 12 -2 assumption was made that this earthquake would rupture the fault at he point on the fault closest to the sites. 12.1.2 -Acceleration Response Spectra Acceleration response spectra for the sites were estimated using spectral shapes appropriate for the preliminary maximum credible earthquake magnitudes and distances of the earthquakes from the These spectral shapes were based on considerations and analyses similar to those described above for peak acceleration. The references cited indicate that spectral shapes, as well as peak acceleration, differ for Benioff zone versus shallow focus crustal earthquakes. The selected spectral shapes were scaled with the corresponding peak horizontal ground acceleration described above to develop the acceleration response spectra. 12.1.3 -Duration of Strong Ground Shaking The duration of strong ground shaking (significant duration) was estimated primarily on the basis of results presented by Dobry and others (1978). In that study, significant duration is defined as the time during which from 5 to 95 percent of the energy of an accelerogram is developed. The significant durations obtained by Dobry and others (1978) using this definition are not much different than durations proposed by other investigators using different definitions of significant duration . . 2 -Preliminary Estimates of Earthquake Ground Motions imated mean (average) values of peak horizontal ground accelerations each site resulting from preliminary maximum credible earthquakes are following: 12 - 3 Den a l i F au lt Castle Mountain Fault Benioff Zone 0.06 g 0.41 g 0.05 g 0.37 g As may be seen by comparison of these mean peak horizontal accelerati values, the Benioff zone and the Denali fault govern the ground moti levels estimated for the sites; the site ground motions due to Castle Mountain fault are relatively small. , For the Benioff zone the Denali fault, the estimated mean acceleration response spectra for damping ratio of 0.05 are illustrated in Figure 12-1 for the Watana s and in Figure 12-2 for the Devil Canyon site. The duration of strong ground shaking at the sites was estimated to 45 seconds for preliminary maximum credible earthquakes on both Benioff zone and the Denali fault. In summary, the results of these preliminary studies indicate that, o the known faults with recent displacement in the site region~ the Benioff zone is expected to govern the levels of peak horizontal acceleration, response spectra. and duration of ground shaking. 12 -4 "'T1 G) c :JJ m r:-' en ctl (f) c 0 ·.;::; ctl 0.8 w 0.6 (]) (.) (.) <( ctl .... .... (.) (]) 0.. (f) 0.2 0.03 NOTE 1. ap is peak horizontal acceleration. 0.1 0.3 3 Period (seconds) ) I i I i I', i I' : i 10 PRELIMINARY MEAN RESPONSE SPECTRA AT THE WATANA SITE FOR PRELIMINARY MAXIMUM CREDIBLE EARTHQUAKES ON KNOWN FAULTS WITH RECENT DISPLACEMENT ~ ~--------------------------------------------------------------------------------------------------------------------------------------J ('") 0 z C/l c r --i )> z --i C/l ~ Ol (11 (X) )> 0 "' n "' 3 o- ~ <D !Xl a , CJ c ::0 m N ~ C) ro (/) c:~ 0 ·.;:::; (1J ,_ QJ 0.6 QJ u u <( (1J ,_ """ u QJ 0. (/) 0.03 0.1 0.3 1 3 10 Period (seconds) PREliMINARY MEAN RESPONSE SPECTRA AT THE DEVIL CANYON SITE FOR PRELIMINARY MAXIMUM CREDIBLE EARTHQUAKES ON KNOWN FAUlTS WITH RECENT DISPLACEMENT h-----------------------------------------------------------------------------------------------------------~ -CONCLUSIONS of conclusions have been drawn from the results of the inves- conducted to date. One set, designated feasibility conclus- s, are those considered important to evaluate the preliminary ibil ity of the Project. The second set, designated technical elusions. are those related to the scientific data collected, sets of conclusions are discussed below and form the basis for the sed 1981 study plan (Section 14). Feasibil i us ions No faults with known recent displacement (displacement in the last 100,000 years) pass through or adjacent to the Project sites. The faults with known recent displacement closest to the Project sites are the Denali and Castle Mountain faults. These faults~ and the Benioff zone associated with the subducting Pacific Plate (at depth below the Project site), are considered to be accepted seismic sources. Preliminary maximum credible earthquakes for the Denali and Castle ~1ountain faults and the Benioff zone have been estimated as a: magnitude (fvls) 8.5 earthquake on the Oenal i fault occurring 40 miles (64 km) from the Devil Canyon site and 43 miles (70 km) from the \~atana site; magnitude (Ms) 7,4 earthquake on the Castle Mountain fault occurring 65 miles (105 km) from the Devil Canyon site and 71 miles (115 km) from the Watana site; and magnitude (Ms) 8.5 earthquake on the Benioff zone occurring 37 miles (60 km) from the Devil Canyon site and 31 miles (50 km) from the Watana site. 13 - 1 (d) Within the site region, 13 faults and lineaments have been j to need additional investigation to better define their pot affect on Project design considerations. These 13 faults lineaments (designated significant features) were selected on basis of their seismic source potential and potential for s rupture through either site. Four of these features are vicinity of the Watana site and nine are in the vicinity Devil Canyon site. (e) At present, the 13 significant features are not known to faults \'lith recent displacement. If additional seismic geol studies show that any of these features is a fault with displacement, then the potential for surface rupture through site and the ground motions associated with earthquakes on fault will need to be evaluated. (f) Preliminary estimates of ground motions at the sites were made for the Denali and Castle f~ountain faults and the Benioff zone. these sources, the Benioff zone is expected to govern the levels of peak horizontal ground acceleration, response spectra, and duration of strong shaking. The ground-mot ion estimates are preliminary in nature and do not constitute criteria for design of project facilities. The site ground-motion estimates will be made final and the design criteria will be developed as part of the next phase of study. 13.2 Technical Conclusions (a) The site is located with the Talkeetna Terrain. This tectonic unit has the following boundaries: the Denali fault to the north and northeast; the Totschunda fault to the east; the Castle Mountain 13 - 2 fault to the south; a broad zone of deformation and volcanoes to the west; and the Benioff zone at depth. The northern, eastern, and southern boundaries of the Talkeetna Terrain are major fault systems along which displacement has occurred in Quaternary time. The Benioff zone beneath the Tal- keetna Terrain represents the upper margin of the Pacific Plate which is being subducted beneath the North American Plate. The western boundary is a broad zone of deformation and volcanoes which does not appear to have brittle deformation occurring along a major fault. The Talkeetna Terrain appears to be acting as a coherent tee tonic unit within the present stress regime. Major strain release occurs along the fault systems bounding the Terrain. Within the Terrain$ strain release appears to be randomly occurring at depth wi in the crust. This strain release is possibly the result of crustal adjustments resulting from perturbation imposed by the Benioff zone and by stress (associated with plate motion) imposed along the Terrain margin through the Terrain. The only fault system within the site region (within 62 miles (100 km) of either Project site) which is known to have had displacement in Quaternary time (the last two million years) is the Denali fault. This fault is approximately 40 miles (64 km) north of the sites at its closest approach. The Castle Mountain fault system is immediately south of the site region. This fault system has had displacement in Quaternary time. Within the site region, 48 candidate significant features have been identified. These features are faults and lineaments for which no evidence of recent displacement was observed, but for which evi- dence of precluding recent displacement has not been demonstrated. 13 - 3 (f) Of the 48 candidate significant features, there are 13 signific features l'ihich the results of this study suggest need addition investigation. These 13 features were selected on the basis their seismic source potential and potential for surface rupt through either Project site. Four of these features are in vicinity of the Watana site and include the Talkeeetna thrust fau (KC4-1), the Susitna feature (KD3-3), the Fins feature (KD4-27) and 1 i neament KD3-7. Nine of the features are in the vicinity o the Devil Canyon site and include fault KDS-2 and lineaments KCS-5 KDS-3, KDS-9, KD5-12, KD5-42, KD5-43, KDS-44, and KD5-45. (g) No evidence of the Susitna feature has been during this study. Reconnaissance level aerial has produced no evidence of a fault in bedrock deformation in overlying surficial units. Review of aerial gravity and magnetics data shows no evidence of major tectonic dislocation. Earthquakes correlated with the southern portion of the feature by Gedney and Shapiro (1975) occurred at depths greater than 43 miles ( 70 km). These focal depths suggest that the earthquakes occurred on the Benioff zone well below the crust and well below the extent of the Susitna feature, if the 1 atter is a fault. The feature may be the of glaciation of stream drainages whose alignment reflects struc- tural control such as joints or perhaps folding. (h) The Talkeetna thrust fault is a northeast-southwest trending fault which may dip either to the northwest or the southeast. The northeastern continuation of the fault is the Broxson Gulch thrust fault resulting in a 167-mile (270-km) long fault that passes approximately 3.5 miles (5 .4 km) upstream of the proposed Watana 13 -4 site. No evidence of displacement younger than Tertiary in age (approximately two to several tens of millions of years old) has been reported for either the Talkeetna or Broxson Gulch thrust faults. However, anomalous relationships in deposits of Tertiary on the north side of the Susitna river were observed during this investigation and may be related to faulting. Seismicity within the Talkeetna Terrain can be clearly delineated as crustal events occurring at depths to approximately 5 to 12 miles (8 to 20 km) and as Benioff zone events which occur at greater depths. The depth to the Benioff zone increases from approximately 25 miles (40 km) in the southeastern part of the site region to more than 50 miles (80 km) in the northwestern part of the microearthquake study area and more than 78 miles (125 km) in the northwestern site region. The largest reported historical earthquake within the site region is the magnitude (Ms) 6-1/4 event of 1929 which occurred approx- imately 25 and 31 miles (40 and 50 km) south of the Devil Canyon and Watana sites, respectively. Four earthquakes greater than magnitude (Ms) 5 have occurred during the period 1904 through August 1980. Earthquakes as large as magnitude (~1s) 5 to 5-1/2 may possibly occur in the site region without direct associ at ion with surface fault rupture. Such events would probably be constrained to rupture planes deeper than 6 miles (10 km). The largest crustal event recorded within the microearthquake study area during 3 months of monitoring was magnitude (ML) 2.8. It occurred 6. 8 miles (11 km) northeast of the Watana site at a depth of 9.3 miles (15 km) on 2 July 1980. 13 - 5 (m) Two clusters of microearthquake activity were observed withi microearthquake network during the three-month monitoring These two clusters occurred in the same general vicinity e the southern portion of the Talkeetna Thrust fault. These cl of seismicity occurred at depths of 5 to 12 miles (10 to 20 One of the clusters gives a composite focal plane mechanis N2rE, dipping 50°NW, consistent with local geologic trends. sense of movement is reverse (toward the southeast) with a dex component of slip. (n) The clusters of microearthquake activity described in (m) appear to be related to a small subsurface rupture plane that not extend to the surface. These clusters do not appear related to the Talkeetna thrust fault. (o) Seismicity in the vicinity of the site, including the clus described above, appears to reflect relatively small-seale cr adjustments at depth in the crust. These adjustments may related to stresses imposed by the Benioff zone and/or by pl motion. (p) No association of microearthquake activity with candidate s nificant or significant features is apparent on the basis information obtained to date. (q) The two reservoirs are considered as one reservoir This combined Watana-Devil Canyon reservoir waul d be among deepest and largest in the world. It is concluded that the likel hood of a reservoir-induced earthquake of any size within t hydrologic regime of the proposed reservoir is high (0.9 on a sc of 0 to 1); this is primarily because water depth has a apparent theoretical and empirical correlation with the ace of reservoir-induced seismicity. 13 - 5 f'rl'l 11~1 '1nry tRa.>lmum credtbl• e.art•IIH"e:: (i'1'1C£s) h~~e h!!i!ll ~ti •R ll!'tl fOI' t;I"UHai fll.llt•' Wltfl f'H.Il,.,~ :S1SIIlc1CIIIl1erl t in ~11d !dl&~t'l\t t a ~fie ~1\e r~yi1111 att\1 ttJI lhl ligntofr ~one; ntr f'Mrc f<ll tl'l u.tnlll f<l•llt 1s ~sL llliMted lu "" 4 "'~9rd1;ude ("sl &.:. v•nt ocour - rtnq All otllles lb~ lm) rront tl'lr Oavil Cilnyon sa nil IIJ ~ ];;!!. !11 1\'11 ) fro; U•'" lc~t••"' ~ite. l nll ~!'ICE for tt·~ C~t-tll! 1'19\lfl '-alr~ ~4~t1r is eHit.ett.il ta l)t 11 ma1,1 nH1JcJ e (M~) 7,4 ~itlt. 01:urr lfl<l 65 mq~ (105 ""' "' lilt De~il C:.nyo., !>h~ Jtid '' t~l1~• Ill'> < ) r r01~ the 14altn• •"" TIll! Plo'lE for ti\P lilltlln 1 I ltHt8 •• e .. II" .nee ~u or a mo\,~nlttH1r \M!) e 5 e•Errt occurr 1tt11 ~1 1111les (':10 iu'l) benelll.h I ll!! ~~~ltln~ SIC• anll ~1 11:5 1&0 ~1 111 l t i'II!'O~Il the ue.,.11 t.a,.ynro 1 t.l'l 11 -1 Plan proposed study plan is designed to provide additional information Project design in accordance th the Plan of Study (Acres American ·~ 1980). This information will include data on the characteristics the 13 significant features and a subsequent refined assessment of potential for moderate to large (magnitude (ML) > 5) reservoir- uced earthquakes. From these studies, a refined estimate of earth- ground mot ions at the sites can be made and earthquake ground criteria can be developed for the Project. proposed study plan is expected to be evolutionary in nature. , the details of the plan can change during the course of the The plan is to: Conduct a detailed Quaternary geologic investigation. This inves- . tiga.tion will include research of available infonnation of recent geologic deposits, weathering rates, and glacial history; interpre tation of large-scale aerial photographs; mapping of Quaternary deposits; and age dating. The purpose of this investigation will be to identify and obtain ages for Quaternary deposits. These deposits can then be used to evaluate the recency of displacement a 1 ong f au l t s • Obtain and analyze low-sun-angle photography around both sites and along the Talkeetna thrust fault and Susitna feature. The purpose of these studies will be to look for evidence suggestive of recent fault displacement. If such evidence is observed, the locations identified on the low-sun-angle photographs will be examined during the geologic field studies. 14 -1 (c) Conduct field geologic studies of the 13 significant featur These studies will include additional air photo analysis a field mapping in appropriate locations. They can also test pits, trenches, geophysical surveying, borings, dating. (d) Conduct calibration studies along either the Denali or Cast Mountain faults. The calibration can include field mappi air photo analysis, and trenching as appropriate. The purpose these studies will be to provide detailed information on the styl amount, and rate of deformation on faults with recent displacement Thus, during the field studies of the significant features, characteristics of the significant features will be calibr against the degree of confidence in judgments made about fault displacement. (e) Design a program manu a 1 for future se i smo logic network monitor.:. ing. The manual will summarize data recording, interpretation, and documentation procedures. The purpose of the manual will be to provide guidelines for obtaining additional high quality seismologic data for the project. (f) Re-evaluate the estimated potential for reservoir-induced seis- micity by incorporating the results of the geologic field studies. The presence or absence of faults with recent displ acernent within the hydrologic regime of the proposed Watana-Devil Canyon reser- voir will affect the potential for moderate to large magnitude (Ms) > 5 reservoir-induced earthquakes. After the field studies are completed, theoretical modeling and additional statistical analyses can be conducted to assess this potential. (g) Finalize the estimates of earthquake ground motion at the Project sites. This will be done after the seismic geology studies are performed to assess the seismic activity of significant features. 14 - 2 (h) Develop Project earthquake ground motion design criteria based on the results of the ground motion evaluations. 14 - 3 ENDIX A -ANNOTATION AND DOCUMENTATION PROCEDURES FOR THE GEOLOGIC INVESTIGATI 1 -Introduction appendix describes the procedures used to annotate and document ida.te features during the geologic investigation. The geologic nvestigation included literature acquisition and analysis, acquisition interpretation of existing remotely sensed imagery and photography, field reconnaissance studies. The procedures used during the inves- at ion can be considered as two sets--one set used prior to and the used during the field reconnaissance studies. hJo sets of procedures were developed prior to initiation of the logic investigation. Revisions were made during the course of the igation to accommodate changes in conditions which developed. The purpose of the procedures was to ide a systematic method of annota- ion and documentation to be used during the review of data sources for he recording of pertinent information, for the transferral of that in- ormation to appropriate base maps, and for the recording of field ob- ations. This method of annotation and documentation was designed to ide repeatable and accurate results ich could be r~eviewed by an A summary of the annotation and documentation procedures is shown in Examples of the documentation forms are included in this appendix. Completed forms for each candidate feature are filed in the project master file; they are not reproduced in this report. A 1 A.2-Fault and Lineament Annotation and Documentation Proced A.2.1 -Literature Review Form SHP-2 Purpose The purpose of this procedure was to outline the steps for documentation of the literature review. Form SHP-2 (Fig A-2), used for the documentation, was designed to meet the lowing goals: (a) To provide documentation for each reference; (b) To provide an easily retrievable, brief summary of the da contained in the reference; (c) To provide a quick reference for faults or lineaments were identified or discussed in the reference; (d) To provide a full reference citation for the ogr aphy. Procedure The following is a summary of the procedures used to complete selected portions of the form. At the top of the sheet, an (X) is placed by the field of study emphasized in the reference; a check (tl) is placed by the fields~ of study that are considered to be of secondary emphasis in the reference. The project reference file is divided into fields of study as those listed at the top of the page. A - 2 The original reference documentation sheet is filed alphabeti- cally.by the lead author's last name in the project master file. The reference and a copy of the reference document at ion sheet is filed under the field of study emphasized in the reference, i. e., the fie 1 d marked with an (X). A copy of the reference document at ion sheet is also filed under the heading of the sec- ondary fields of emphasis marked with a check(~). This procedure provides a cross reference system for references. If, for example, information on age dating is needed, a review of the file under the heading of age dating provides all references (and reference documentation forms) which emphasize age dating. In addition, reference documentation sheets are present for other references that don't emphasize age dating but which nevertheless contain usable age dating data. The name of the person who reviewed the reference is entered. along with the date of the review. If a copy of the reference is not in the project file, the 11 no" is circled on the form and the location of the reference (e. g., Woodward-Clyde Consultants Library, UCLA Library) is written at the end of the Full Citation section. A complete and accurate citation is included, using the format given in Bishop and others {1978). Illustrations such as maps and cross sections which are pertinent to fault studies are listed. The title and scale of the illustration are also in- c 1 uded. The geographic area covered in the reference is described using physiographic feature names and/or geographic names. If appro- priate, more specific locations are described by citing 15 minute quadrangle sheets? township and range, or longitude and latitude. A - 3 The summary provides a brief synopsis of the reference contents. Data that may be useful in the seismic geology study are noted, and the quality of those data with respect to the purposes of the project is indicated. For references marked "not useful, 11 a brief explanation of why the reference is not useful is provided. Structural elements (faults and lineaments) identified in the reference that occur within a 62-mile (100-km) radius of both dam sites are transferred to the base map and are assigned a map code number using the procedures discussed below in Section A.2.5. The map code number and names, if applicable, of all structural e 1 em e n t s c it e d i n t h e r e f e r e n c e a r e 1 i s t e d o n F o rm S H P -2 . A.2.2 -Remotel Sensed Data Form SHP-4 P ose The procedures described below include the documentation methods that were used during the interpretation of 1 ineaments on re- motely sensed data. The key sect ions of the procedures are the annotation of mylar overlays and the completion of the remote sensing lineament worksheet (Form SHP-4). An example of the form is shown in Figure A-3. The coverage of remotely sensed data used for this investigation is shown in Figures A-4 and A-5. Procedure All interpretation of remotely sensed data was annotated on mylar overlays. The overlay includes registration marks, image type and scene identification number, the project number, the inter- preter1s initials, and the date of interpretation. A -4 /-\ll lineaments interpreted to be possib e faults or possible faults with potential recent displac~~ent were delineated on the overlay. Lineaments meeting the leng -distance screening cri- teria (described in Section 3.2) were assigned a remote sensing code number by using procedures described below in Section A.2.3. This interim remote sensi code number was written on the mylar overlay adjacent to the lineament. Lineaments ich did not meet length-distance screening criteria were annotated with an X. After all lineaments were annotated with ei an interim remote sensing code number or an X, overlays were filed in the project master file. Lineaments ich met length scribed on the remote sens i istance screening criteria were de- lineament worksheet (Form SHP -4). The intent of these descri ions was provide a cone i se list and summary of geomorph c expressions wh could ssibly sug gest that a feature may be a fault and may have recent di ace- ment. Key l oc at ions to examine t feature were re- corded to facilitate examinat studies. A.2.3 -Assi nment of Remote Sensi during f d reconna ssance Numbers After lineaments were identified on remotely sensed data, recorded on mylar overlays, and screened usi the l th istance criteria descri in Section 3.2, they were assi ed a 3-element remote sensing code number. The first element of the remote sensi code number is a 1 etter which designates the type of remote sensi imagery on ich the lineament is expressed. The letter symbo s used were: A 5 A-LANDSAT IMAGE, MSS BAND 7, 1:500,000 scale print; B -LANDSAT IMAGE, MSS BAND 7, 1:1,000,000 scale negative; C -LANDSAT IMAGE, MSS BAND 5, 1:1,000,000 scale negative; D -High-altitude near-infrared (IR) color print, approximately 1:125,000 scale; E -Low-altitude black-and-white panchromatic print, approximately 1:20,000 to 1:50,000 scale. The second element of the remote sensing code number consists of the flight line and frame identification number, for aerial photo- graphy, and the scene identification number, for LANDSAT imagery. The third element of the remote sensing code number is a number from 1 to 11 n," for "n" number of lineaments which have centerpoints located on that particular photo or image. A small letter (e. g., 1a, 1b, lc) can be used to identify splays, 1 ineament segments, etc. that are considered to be part of a larger, through-going lineament. Two examples of remote sensing map code numbers for a lineament are: D13700-3 and D13700-3a The first remote sensing code number identifies the lineament as lineament number 3 that has been interpreted on high-altitude, A - 6 near-IR color photograph 700 taken on fl ightl ine 13. The second remote sensing code number identifies a lineament that is a splay off lineament 013700-3. Only the third element of the remote sensing code number was marked on the photo or image overlay. The complete remote sensing code number was recorded in the space provided on the remote sensing lineament worksheet (Form SHP-4). ,1-\fter the interpretation of the various types of remote sensing imagery was completed, all worksheets for a given lineament were reviewed. All geomorphic expressions and the corresponding key locations to be examined in the field were summarized in Items A.2 (Geomorphic) and A.4 respectively on the fault and lineament data summary sheet (Form SHP-3, shown in Figure A-6). The remote sensing code number was cited as the data source for these entries on Form SHP-3. A.2.4 -Transfer of Lineaments Identified on Remotel Sensed Data to Base If a lineament interpreted during the remote sensing analysis did not duplicate the plotted 1ocation of a lineament or fault ide i- fied from the literature review, then the lineament lll!as plotted on the map and assigned the next available map code number us i procedures described in Section A.Z.5 below. The map code number was recorded on Forms SHP and SHP-4. If a l inearnent mA fault (identified from the 1 iterature review) had already been p1otted in approximately the same location as a 1 i neament identified during the remote sensing analysis, then the lineament was not added to the base map. Instead, the map code A - 7 number for the feature already on the base map was assigned to the lineament and recorded on Form SHP-4. In addition, the remote sensing code number was listed in the Data Sources/References Sec- tion of Form SHP-3, and the geomorphic expression of the lineament was summarized on Form SHP-3. If a lineament was longer than a lineament or fault which had al- ready been plotted at the same location and if the center point of the longer lineament fell within a different 15 minute quadrangle, then a map code number was assigned to the longer lineament (using the procedure described in Section A.2.5 below) and the map code number for the longer lineament was assigned to replace the map code number for the shorter fault or lineament. This replacement involved immediate correction of forms filled out for the previ- ously plotted shorter fault or lineament. If a lineament was discovered to be a splay of~ or closely parallel to, a previously plotted fault or lineament, then either a new map code number was assigned to the lineament or the existing map code number was modified (using the la, lb designation described in Section A.2.3) and assigned to the lineament. If the latter procedure was used, Forms SHP-3 and SHP-4 were annotated to docu- ment the presence of subsidiary lineaments to the previously identified fault or lineament. Code Numbers to Faults and Lineaments Purpose The purpose of this procedure was to provide the basis by which faults and lineaments evaluated during this study would be labeled. The alpha-numeric code (termed map code number) was as- signed and used to identify faults and lineaments shown on pro- ject base maps, remote sensing overlays, and documentation forms. A -8 rocedure Our i ng the 1 iter ature review and remote 1 y sensed data i nterpre- tat ion, a map code number was used for each 1 ineament or fault that was entered on the base maps and various documentation forms. The method of constructing the map code number for (a) faults and lineaments identified in the literature and (b) linea- ments identified on remotely sensed data is described below. All faults and lineaments (including those from published geophy- sical data) obtained om the literature review and located with- in the 62-mile (100-km) radius of both sites were plotted on base maps and assigned a 3-element map code number. In addit • the Castle Mountain fault and associated branches and splays which 1 ie outside the 62-mile (100 adius were also assigned map code numbers because the fault is a boundary fault which was in- cluded in the scope of this investigation. The first element of the map code number is a one letter symbol ich designates 2 o quadrangle map on which the approximate center point of the fault or 1ineament is located. The letter symbols for the appropriate 2° quadrangle maps are as follows: A -Anchorage G -Gu 1 kana H -He a 1 y ~1 McKinley T Talkeetna K Talkeetna Mounta ns v Tyonek X -t4t. Hayes The second element of the map code number is a bw-unit alpha- numeric symbol wh describes t 15 minute quad 1e map on A 9 which the approximate center point of the fault or 1 ineament is located. This alpha-numeric symbol is based on the U. S. Geologi- cal Survey's 1 etter/number matrix that identifies the 15 minute quadrangle maps within each 2" quadrangle map, as indicated below. 6 5 4 3 2 1 0 c X B A For example, within the Talkeetna 2" quadrangle map, B3 would de- note the 1 ocat ion of the 15-minute quad rang 1 e map in the south- central portion of the 2" quadrangle map as indicated by the X in the above illustration. The third element of the map code number is a number from 1 to "n 11 for 11 n11 number of faults or 1 ineaments which have center- points located on the 15-minute quadrangle map just described. A small letter (e. g., 1a, 1b, 1c) is used to identify fault splays, fault segments, etc. that are considered to be part of a larger through-going fault or lineament. Two examples of a map code number for a fault or lineament are: TB3-3 and TB3-3a A -10 The first map code number identifies the feature as fault or lineament number 3 having a centerpoint in the 83 15-minute quadrangle of the Talkeetna 2° quadrangle. The second map code number identifies a fault or lineament that is a splay off the fault or lineament TB3-3. Purpose The fault and lineament data summary sheet (Form SHP-3, Figure A-6) is the key form of the project. Its purpose is: (1) to summarize the information used to identify and characterize (a) faults or lineaments described in the 1 iterature or (b) 1 inea- ments identified by remotely sensed data interpretation which meet the length-distance screening criteria; and (2) to track the progress of the field work for each feature and to verify that work has been completed or that addit al field ies are considered necessary. Procedures The fault and lineament data summary sheet (Form SHP ) has been completed as described below for every fault or lineament identi- fied in the literature and for all lineaments identified on remotely sensed data meeting the project screening criteria. Faults and Lineaments Identified in the Literature Section A.l \'las completed for all faults and lineaments identi- fied in the literature including those inferred from geophysical data by Woodward-Clyde Consultants or by others. A -11 If. the fault or 1 ineament was judged not to be a candidate sig- nificant feature on the basis of the length-distance screening criteria (described in 11 Significant Feature?11 initialed and dated the Section 3.2). 11 N0 11 was written after The person making the evaluation then decision on the back of Form SHP-3. No other data were entered on the form and it was file9 in the pro- ject master file. If the fault or lineament was judged to be a significant feature on the basis of the length-distance screening.criteria, 11 Yes 11 was written after 11 Significant Feature?" The person making the eval- uation then initialed and dated that decision on the back of form SHP-3. The remainder of the form was completed with all appli- cable data as described in the following paragraphs. Sections A.2 through A.4 were completed prior to the field recon- naissance studies. Applicable data were summarized and keyed to the appropriate data source or reference cited on the back of the form. Section A.4 was of particular importance to facilitate field checking of the feature. Section B was completed during the field reconnaissance studies. Section B.l was completed after the initial examination of the feature during the field reconnaissance studies. If additional work was judged to be necessary. Items 8.2 and 8.3 were completed as appropriate. Lineaments Identified on Remotel Sensed Data Sections A and B were completed for all lineaments that met length-distance screening criteria. The procedures for complet- ing the form were the same as those discussed above for faults and 1 ineaments. A -12 References and Data Sources All references and data sources were entered on the back of the form. Reference citations include the author(s) and date. Each data source or reference was assigned a number. This number is listed in Section A following pertinent data from the references or data source. A.3 -Field Reconnaissance Documentation Procedures Purpose During the field reconnaissance studies, the procedures described be- low were used to observe candidate features and to document the observations. As a part of these procedures, Forms SHP-6, SHP and SHP-8 \>Jere used to maintain the uni of data collected and recorded by the project team members. Procedures For maximum effectiveness, the field geologists ordinarily worked in two-person teams. During aerial recon aissance, the geologist seated in the front of the aircraft had prim responsibility for navigation, as well as responsibility for observations of morphologic features visible from his or her side of the aircraft, The second geologist, who occupied a rear seat on same side the aircraft, had primary res pons ib il ity for document at ion of i rmat ion at ing both to his or her own observations that the ot team member and had a secondary responsibility for veri t locations of the observations. Photography of the features observed was a shared responsibility. In order to gain the lest benefit of the exper- ience of each member of the f i d team and to ensure a common basis A -13 for arriving at an informed opinion about the origin of the observed features, each previously identified 1 ineament was flown in both d i r ec t i o n s . For some long faults or 1 ineaments, it was necessary to examine the feature in detail at a number of different locations. Aircraft landings were made, where possible, to study fault-related features and features that could possibly have been related to recent fault displacement. Each location which was studied in detail along a given feature was given a separate site number~ and a copy of Form SHP-6 was completed for these locations. Each landing site was marked on the appropriate 15-minute quadrangle map with a given symbol. Where appropriate, measurements were made of: the strike and dip of features; slopes of the ground surface; length and height of scarps; and the amount of displacement or diversion of streams. Measurements were taken by Brunton compass, by estimation, or by pacing. Where appropriate, samples of bedrock were collected and labeled~ and bedrock geology was mapped in selected areas. Color 35~millimeter photographs were taken of all faults and linea- ments. Photographic data recorded in the field on the photo log (Form SHP-7 shown in Figure A-8) included the map code number of the fault or lineament, the site number, the photograph look direction, the orientation of the lineament in the photograph, and significant observations. {), 14 A.3.1 -Completion of Field Observation Documentation Sheet (Form SHP-6) Purpose The purpose of Form SHP-6 (shown in Figure A-7) was to document observations made for candidate features during field reconnais- sance studies. The form was designed to facilitate the distinc- tion between observations and interpretations, Procedures The field observation documentation sheet (Form SHP-6) was completed during aerial and ground reconnaissance for each candidate feature. All observations in the vicinity of the candidate feature were noted by checking the appropriate entries on Form SHP-6. The only interpretations recorded on the form were entered in Sect ions 3e and 3f for which interpretations of the origin of the feature and estimates of the age of the youngest unit displaced by the feature were made. The study of a fault or lineament was considered complete when the field crew agreed that adequate data had been gathered. Whenever there was uncertainty or disagreement about the inter- pretation of the origin of a lineament that couid have had recent or potentially recent displacement~ a blue symbol \'ias marked on the map and on Forms SHP and SHP-6. This symbol indicated that the feature should be considered further by the principal inves- tigator or by a senior reviewer. A copy of each form was given to the Project Geologist for evaluation by the appropriate personnel. A -15 A.3.2 -Photography Documentation (Forms SHP-7 and SHP-8) Purpose The purpose of the photographic documentation forms (Forms SHP-7 and SHP -8) was to record all photographs taken for each roll of film and ultimately to record all photographs taken of a specific candidate feature. Figures A-8 and A-9 provide examples of these forms. Procedures Prior to the field reconnaissance study, each roll of film was assigned a project roll number (e. g., S-1, S-2). For each roll of film 9 the same project roll number was assigned to a copy of Form SHP-7. All photographs taken on a roll of film during the field reconnaissance study were recorded on the corresponding copy of Form SHP-7. During field reconnaissance studies~ photo- graphic data were recorded as discussed at the end of Section A.3 (immediately prior to Section A.3.1). When a roll of film was finished 9 the date of mailing for processing was recorded at the top of Form SHP-7~ and the corresponding mailer stub was stapled to the form, After the film was developed, all prints or slides were marked with the project roll number, frame number, and map code number. The photographs or slides applicable to the various faults or 1 ineaments were recorded on the fault and 1 ineament photo log (Form SHP=8) and were filed with the other data for that fault or 1 i nearnent, A ~ 16 A.3.3-C letion of Fault and Lineament Index Sheet Form SHP-5 --~--------------------------------------~--------~ Purpose The purpose of this form (Form SHP-5, shown in Figure A-10) was to maintain a summary of the field examination of candidate fea- tures during the 1980 field reconnaissance studies. In addition, the evaluation of these features was monitored with this form. Procedures The information for the first three columns was obtained from the fault and lineament data summary sheet (Form SHP-3). Plotting of the features on the 1:250,000 scale base map and on 15-minute quadrangle maps was recorded in the appropriate column when com- pleted. Examination and review in the field, and decisions regarding whether additional work was considered to be necessary were recorded in the appropriate columns during the field inves- tigation. The last two columns were completed by the end of the 1980 field season. A -17 n 0 z In c: r );! 2 -l 00 , G') c :D m )> . ...... Annotate o11erlay and me. (A.2.2) Plot on base map. (A.2.4) Assign map code number, (A.2. Record numoor on map,(A.2.4) Fault and Lineament Summary sheet SHP-3, (A.2.6) and Remote Sensing Lineament Worksheet SHP-4. (A.2.4) NOTES NO Assi911 remote rensing code numb<sr. (A.2.3) Document & complete Remote Sensing Lineament Work:Uwet SHP-4. (A.2.2) Assign existing map code number,(A.2.4) Record number on Fault and Lineament Summary shoot SHP-3 (A.2.6) and Remote Sensing Lineament Worksheet SHP-4. (A.2.4) 1. (A.2. 1) is report section in which a particular documentation procedure is described. 2. SHP-4 is form numbar on which the documentation is recorded. Plot foolt on bare m8p. (A.2.5) Assign map code number. Record number on map and on Fault !lnd Lineament Summary sheet SHP-3. (A.2.S) Does fault meet screening criteria? (3.2) YES Complete documentation on Fault and Lineament Summary sheet SHP-3; (A. 2.6) Record on Fault and Lineament Index sh'*lt SHP-5. (A.3.3) Field observations recorded on Field Documentation sheet SHP-6, (A.3. 1) Photo Log SHP-7 and Fault and Lineament Photo Log SHP-8 (A.3.2) Document on SHP-3 and file. (A.2.6) fLOW DIAGRAM Of DOCUMENTATION PROCEDURES • GEOLOGY ( ) STRUCTURAL REMOI'E SENSING ( ) TECirniCS GEN. GEOLCGY ( ) RESOURCES ( ) SEISMICITY ( ) AGE ffiTING ( ) 'oRPP.t<tF:N(cE rxx:UMENTATION SHEET HYOOOELECTRIC PROJECI' No. 14658A ffiTE: Copy ..,.i-n-;F""'i--:-1-e-: ---,(,-y_e_s,-) .....,(,_n-o')---- IWJSTRATIONS, TITLES AND SCALES: ------------------ SUMI-lARY OF OJNTEm' AND QUALITY OF REPORI' WI'IH RESPECI' 'IQ PROJECT: -------- ffiTA USEFUL ( ) Not Useful ( ) Explain: __________________ _ STRLJC'IURAL ELDlENIS IU:m'IFIED (ASSIG< IDENI'. NUMBER, FilL OUI' ll\TA SHEET, FDR EACH UX:ATE rn BASE MAP) • FAULTS LINEAMENTS (continue listing on back of page) SHP-2 Page 1 of 1 Revision #0 17 March 1980 REFERENCE DOCUMENTATION SHEET (FORM SHP-2) DE CONSULTANTS 14658A December 1980 FIGURE A-2 SHP--4 TYPE: SUSITWI HYDROELECTRIC PROJECT 14658A -Task 4 RD'OI'E SENSING CODE NJ. tU. ____________ _ FLIGH1'LHJE I'D, MI\P CODE I'D. --------------------- D'ITE FILWN IMAGE QIJI\Ll'N: Goo::i Fair Flxlr SENSITIVITY -------------------QUW MAP ----------------------- It?TERPRETER' 5 C:CMMENTS Page 1 of 1 By ___________ IATE: ________ _ ORIENTATIOO BY ----------------------ffiTE _________ _ Revision #l 10 April 1980 REMOTE SENSIN.G LINEAMENT WORKSHEET (FORM SHP-4) DE CONSULTANTS 14658A December 1980 FIGURE A-3 CANADA 16-241 16-238/ LEGEND NASA designated photograph flightline number and exposure numbers U-2 PHOTOGRAPHY FLIGHTLINE COVERAGE MAP ARCTIC OCEAN I )>I r\ )>I (/')\ "'-\ 'l>, I \ I LIMIT OF LANDSAT COVERAGE \ -Devil Canyon Site -Watana Site DE CONSULTANTS 146158A December 1980 GULF OF ALASKA \ LANDSAT IMAGERY COVERAGE MAP 0 100 200 300 400 Miles ~~?43~~=b4@~~~~~~==~1 0 100 200 300 400 Kilometers FIGURE A-5 FAULT AND LINEAMENI' ffiTA SUHMA.RY SHEET SUSI'INA. HYDROELECI'RIC PROJEcr 14658A -Task. 4 D;TA FRCM LITERATURE OR REMarE SENSING INTERPREI'ATICN 1. C!ii<AACTERISTICS: FEATURE Nf>~lE FAULT ( ) LINEA.HD>JT ( ) W\P CODE N.J. DIST. FRCM SI;;:;T;:;-E~("'~l""I') _____ LENGTH (MI) SIGNIFICANT FrA'IURE? --- WII.1l'H (IT) ORIENIATICN LCCATICN RElATIVE 'ID IAM/RESER- 2. EVIDEt\'CE USED 'ID IDENI'IFY FEATURE: GECMORPHIC GEOLCGIC GEDPHYSICAL SEISMOLCGICAL 3. Oi'iAACTERISTICS OF FEATURE IDENTIFIED AS A FAULT: FAULT TYPE: NOR11Z'\L ( ) THRUST ( ) REVERSE ( ) STRIKE-SLIP ( } OBLIQUE-SLIP ( ) UNITS OR FEATURES DISPLACED, AGE, A<"iOUNT: ---------------- EVIDENCE FDR ACTIVE OR !Nf>CTIVE FAULT: GEOLCGIC SEISMOLCGIC 4 • I..CCATIOOS 'ID EXAMINE FEA. TlJRE: FIELD INVESTIGA.TION SUHMARY 1. lliiTIAL FIELD RECON: LA.TE BY 2. ADD. AERIAL P£CCN. NEEDED? ------;:m"'"'TE OO""'ND=UCTE==D----.,_BY:-:-~~:-_____ _ 3. GROUND STUDIES NEEDED? ffiTE OJNJXJCTED BY 4. CRIGIN OF FEATURE ------------ 5. ClJNSIDER TRENCHIN:; LOCATION ----------------~--- Revision #1 4 April 1980 FAULT AND LINEAMENT DATA SUMMARY SHEET (FORM SHP-3) l YDE CONSULTANTS 14658A December 1980 FIGURE A-6 SL'SITir, HYDROCLECT!UC Pfl.QJ!.:CT l4658A -Task 4 Map Code N:J ·---------- r.ocation of field cbservation: (Fault) (Lineament): Site tkl. _____________ _ Q.Jadrangle map-------Dote-------- !):)Cum=ntatwn: Tape fi:J. Side --------- p!Jotographs: Poll ___ Nu:rbers ____ Other -------------------------------- 1. FEAT!JRE. TYPE A. Mor]'holcx;ic: Break in slope; B. Noll!TOrpholcg ic: Linear streams; Ridge; Trench; Saddles; Lit..h:llCXJic contrast Vegetation line of--------' Vegetation contrast between ------------------------------------ Cultural feature ---------OLoer ----------------------------- 2. ITAC!URE MORPHOLCGY A. Descriptive Classificatio:1: Slope; Ridge; Terrace; Plateau; Plain; Rolling hills; Hwmocks; Fan or cone; Valley; Canyon; Other ------------- B. Genetic Classification: Floodplain; Bar, meander scar; Shoreline; Sand D.mes; I..oess; Solifluction c. Features of Special Interest: Displaced features alof"B linean1ent {yes) (rn) i rrype of offset feature: Terrace; Moraine; Strea:~~; Fan; Other -------------- Sense of offset ______ ; Alrount of offset------' Age of o!'fsct ----------------- Alluvial fans along linearrrent (yes} {no}: Terraces crossing lineaJ1'.ent (yes) {no}; Scarp along lineament (yes) (no); Cescription ------------------------------ D. Gecr.orphlc Fault Features: Folded or warped dep:.Jsits; Open f .1ssure; Triar1gular facets; Sag pond or sag; Graben; Other --------------------------------------------------------------- Feature in ------------------------------------------------------------------------------------------- 3. FEAruRE =LCGY A. Feature In: Bedrock; Unconsolidated sediment; tot~ B. Bedrock Type: Igneous; Volcan1c; Sedline;1tar"j; C. Unconsolidated Sedinent Origin: _Fluvial; Mass \\lasting Colluvial; ?-1eta.mphici Aeolian; La . .ct.:str1ne; Glacial; Volcanic; D. Unconsolidated Sediment Character: Bedded; Unbedded; Sorted; Unsorted; Clay; Silt; Sand; Gravel E. Youngest Unit Crossed by Linea."Tent: _______________________________ Age --------------------------------- F. Origin of Linearnent: 4. HYDROLCGIC Ql,;RACTERISTICS A. Surface: _ Lakeshore; PoOOs or marsh; Streain diversion; Strea;:: entrenchment; Sno,.; banit;:s B. Subsurface: Groundwater tarrier; Cold springs; Hot springs; Pingo; Solifluction lobes 5. SO>.RP OC.SCRIPriCN A. Dimensions: Slope (flax. ) __ ; Slope (A vg.) Height (Hax.) He:ght (Avg.) B. Linearity: _Linear; Curvilinear; Sinuous; Strike ____________________ _ C. Scarp Character: Conti:-tuous; Discontinuous; En echelon; Parallel; D. Scarp Mo:hfication: Rilled; Gullied; Breached; Rounded; Beveled; Buried; Branching Landsl1des; Exposed bedrock 6. a:M."1.0:-1I'S: (Use back of fonn for c:dditional space) SHP-6 Page 1 of 1 D-CLYDE CONSULTANTS 14658A December 1980 Revision #2 18 June 1980 FIELD OBSE DOCUMENTATION SHEET {FORM SHP-6) FIGURE A-7 SUSITNLI. HYDROELECI'RIC PROJECI' 14658A -Task 4 PHaro I.CG Role No. Name ---~c:c--::-,,..--.,---...,_-----Date ------------Film 'l\fpe No. of Frames ASA -------~~-----------Fllm sent for processing: 'Ib By _________ Date ____ _ Fllrr< received from processor: Date Photos sorted by fault/lineament; by,-~~~----~---------------Date _______ _ Map 15 0r1entation Photo Ccxle Site Minute Look of Feature Subject Description/ No. No. No. Quad. Direction on Photo Significant Features 1 2 3 4 5 6 7 0 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 SllP--7 Page 1 of 1 Revision U 10 April 1980 PHOTO LOG (FORM SHP-7) D-CLYDE CONSULTANTS 14658A December 1980 FIGURE A-8 SHP-8 FAULT AND LINE'AMENI' PHOI'O I..(X; SUSI'll\IZI. HYDROELECTRIC PROJECT 14658A -Task 4 or Lineament's Map Code tb. ------------ Photo No. Site Minute Look No. Quad. Direction Page 1 of 1 of Feature on Photo Revision #1 LYDE CONSULTANTS 14658A December 1980 Subject Description/ Features 10 April 1980 FAULT AND LINEAMENT PHOTO LOG (FORM SHP-8) FIGURE A-9 -1> Ol 0'1 00 )> 0 "' n "' 3 cr "' <0 00 0 "'T1 G) c :::0 m ~ _. Map Code No. SHP-5 Quad Plotted on Feature 15' map Name By Date Page 1 of 1 Examined in Field By Date -- Add. Examination Ground Exam. Needed Completed Needed Canpleted Yes /N /N 0 By Date Yes 0 By Date = Significant Reviewed Active Fault Fault By Date Revision #0 Yes /N 0 Yes/No 10 April 1980 FAULT AND LINEAMENT INDEX SHEET (FORM SHP-5) OL---------------------------------------------------------------------------------------------------------------------~ DIX B -1980 MICROEARTH AKE NETWORK INSTALLATION OPERATION AND MAINTENANCE PROCEDURES 1 -Site Selection iminary site selections based on available photos and maps were made re the fieldwork began. When helicopter access became available in e last two weeks of June~ 1980, these selections were refined on the is of the following requifements~ Q The sites must be within 30 miles (48 km) of the Project sites; The net~'llork must provide good geometrical coverage around the sites; The sites must be easily accessible by helicopter; The sites must be on or near competent bedrock; The sites must provide good telemetry paths to the Watana Base c~~P recording site; and To allow for high signal amplificationw the sites must be rela- tively free of background noise created by cultural activities. , ~1Jater. and Table B lists the locations, elevations, and operating periods of all stations used in the study. Three stations (DPC, DCRs B) were moved during the study to provide better location control around a cluster of small earthquakes. The new locations. TKR, SBL~ and UPG were selected on the basis of the same criteria. The network configuration~ as shown in Figure B-1, allowed for earthquake location in the study area even if one or two stations were inoperable at the time of an event. B -1 Woodward-Clyde Consultants B.2 -Instrumentation Two types of microearthquake recording instruments were used for t field monitoring program. The first instrument, the Sprengneth MEQ-800 seismographic recorder, is a battery-powered drum recorder wh provides a continuous analog paper record. seismometer are amplified and drive a galvanometer, which traces amplified signals onto a rotating smoked-paper drum with a sapphi stylus. The instrument is equipped with selectable frequency filter to reduce background seismic noise that may obscure earthquake data Recording is continuous until space on the drum is exhausted, at whic time the smoked paper must be changed. An accurately adjusted quartz oscillator clock provides precise timing marks that are superimposed on the record. The internal clock is synchronized to an external reference clock when the records are changed. Eight t~EQ-800 recorders were operated at Watana Base Camp using tele- metered signals from the remote seismograph station sites. These eight stations that tel emetered the data to the base camp were equipped with a Mark Products L-4C vertical component, short period (1 Hz) seismometer and an electronics package containing a Sprengnether AS-110 amplifier, Spreng nether TC-10 Volt age Contra 11 ed Oscillator ( VCO), and a Man it rom 100 mw radio transmitter. The voltage signal from the seismometer was amplified and converted to a varying-frequency audio tone that was then transmitted by FM radio. The various tones were received by a FM radio receiver at the base camp, demodulated using a Sprengnether TC-20 dis- criminator, and recorded on the MEQ-800 recorders. In some cases, sev- eral VCO tones were multiplexed. Both transmitter and receiver employed Scala antennas. The transmitter station was powered by two 2.5 volt Edison Carbonaire batteries with a DC-DC converter which stepped up the voltage to 12 volts. Watana Base Camp recorders were powered by four 12-volt lead acid batteries that were recharged using the camp generator. B - 2 ----------~, ~~""'~""' second type of instrument used in this study was a Sprengnether -100 three-.component digital event recorder. The DR-100 is designed record intermittently only when a signal is identified as an earth- e according to programmed criteria. When an earthquake is detected, recorder is triggered and the signal is recorded on a magnetic tape The frequency of tape-changes on a DR-100 instrument depends upon the level of seismic activity in the area and upon the success with ich the instrument was adjusted to discriminate between noise signals earthquakes. The three sensors for the DR-100 are also Mark Prod- L-4C seismometers--one is vertically and two are horizontally ori- (north-south and east-west). The vertical seismometer acts as the signal source for the detection algorithm. The operation of the DR-100 is much more complex than that of the MEQ-800. Signals from the seismometers are amplified and converted from analog to digital form before being processed. A logic circuit monitors the incoming vertical-component digital signal and determines if it is earthquake signal, When the trigger criteria are satisfied, the data all three components are retrieved from digital memory and are cassette tape. The DR-100 provides an accurate time record n a manner similar to that of the MEQ-BOO. The triggering criteria are programmed in the field and depend upon the level and nature of the background noise present at each site. At sites having a low and constant background noise level, it is possible to set the triggering criteria to permit the detection of very small earth- quakes and still to have a tape 1 ast for long periods. To prevent the tape from running out too quickly, sites that are subject to large. occasional noise signals, such as those generated by passing vehicles, the triggering criteria adjusted so the instrument is less sensitive to small signals, including small earthquakes. For time corrections, the internal clock of the DR-100 is synchronized to an external reference clock. For this study, the synchronization was B - 3 Woodward·Ciyde Consultants achieved during field operations by using a Sprengnether TS reference; this is a portable quartz oscillator clock similar in to the integral clock of the MEQ-800 seismograph. The refe was calibrated to the international radio time standard, stati using a radio time receiver and an oscilloscope. This allowed accuracy to within several hundredths of a second. Two DR-100 three-component stat ions were installed, one at the dam site (WAT) and the other at the Devil Canyon dam site (DEV). station was powered by three 12-volt lead acid batteries. The meter sign a l s were first amplified with Sprengn ether before being sent to the DR-100 recorders. B.3 -Installation, Operation, and Record Changing The microearthquake network (Figure B-1) was installed during late and the first week in July, 1980, and operation began on the da listed in Table B-1 and shown in Figure B-2. Once the stations installed, a program of maintenance and record changing was establish The frequency of vis its to the stat ions WAT and DEV depended upon th rate of triggering on the DR-lOO's (that is, on the level of activity). On the average, 15 to 20 triggered events could be written on a 15-minute magnetic tape. An average of 4 to 10 events per d triggered the DR-lOO's during the monitoring period, so the magnetic tape lasted 2 to 3 days. Thus, record changing was performed ev other day, except in bad weather. Even if the two digital stations not operating, coverage was provided by the continuous telemetry system. The DR-100 stations required further adjustment of their trigger set- tings during the initial monitoring. All 'transportation from Watana Base Camp to the network stations was accomplished by helicopte~. Routine maintenance of the DR-lOO's consisted of checking and syn- chronizing the internal clocks with the TS-400 reference clock, checking the voltage level of the batteries, and verifying the proper operation of the recorder. B - 4 The eight MEQ-800 smoked paper records required changing every 24 hours. total of sixteen drums were kept at the base camp so that one set of eight could be papered and smoked with carbon-black while the other eight were recording data. Records were fixed (made permanent) with a shellac/alcohol solution to prevent the carbon from rubbing off. Time corrections were made daily using an oscilloscope and the WWV radio time standard. The TS-400 reference clock was corrected daily in the same Gain settings were adjusted to be as high a.s possible (66 to 78 db electronic amplification) but were reduced during periods of excessive noise, such as during high wind and heavy rain. Information that was noted on the back of each smoked paper record is shown in Figure B-3. Routine maintenance of the MEQ-800 recorders in the central recording station included changing low batteries, checking the tele- metered center frequencies. and making sure the drums rotated properly. The routine maintenance checks and any changes in the status of the recording equipment in the central recording station were recorded daily in the central recording station log book. The MEQ-800 recorders were calibrated to give a pen deflection of 14 mm at a gain setting of 72 db with both filters out when a current of 120 micro amps at 6.2 volts was applied with a handcalibrator. Figure B-2 shows the period of successful operation for each station during the three-month period. For some stations, malfunctions of the recorders or delays in changing records caused missed recording time. For the three-month period, 95% of all the possible recording time was successfully recorded with continuous coverage provided by seven or more stations. Table B-1 gives the removal dates for each station at the completion of the field season. B.4 -Record Reading Procedures Smoked paper records from the MEQ-800 s and dig ita 1 tapes from the DR-100 1 s co 11 ected from the field were brought to Watana Base Camp for B - 5 data reduction and analysis. Station information was recorded in the central recording s.tation log book. Identification information for each of the magnetic tapes was listed in the DR-100 tape log book. Magnetic tapes were reproduced on a paper chart recorder, and every triggering event was identified by its 11 0N 11 and 11 0FF" time which was entered on a list of trigger events. The lists of triggered events for stations DEV and WAT were then compared to the MEQ preliminary reading sheets to identify any event that appeared on two or more station records. The paper analog records of these events were produced from the digital tapes using a Sprengnether DP-100 Digital Playback Unit and a strip- chart recorder. All recorded events were then identified as being local, regional, or teleseismic earthquakes and were recorded on the MEQ-800 preliminary reading sheets (Figure B-4). A local earthquake was defined as an event that occurred within or near the boundaries of the network con- figuration (shown on Figure 8-1). The distance of an event from a particular station can be quickly calculated by measuring the time difference between the shear (S) wave and the compressional (P) wave arrival times. Any earthquake having an S-P time of 10 seconds or less at all stations (which time corresponds to a distance of approximately 56 miles (90 km) was defined as a local event. Ten seconds was used as the cutoff for local status since the P-wave travel time between the two most distant stations in the net was approximately nine seconds. An event having an S-P time of 10 to _40 seconds was considered to be a regional earthquake; an event having an S-P time of greater than 40 seconds was classified as a teleseismic earthquake. The P-and S-wave arrival times of the earthquakes were read from the records as precisely as possible. Arrival times could be measured with a precision of 0.025 second on the MEQ-800 records and 0.05 second on the DR-100 records. The P-and S-wave arrival times were entered on computer coding sheets in the format required for computer analysis. B - 6 maximum amplitude of the waveform and the total signal duration of earthquakes recorded at each station were measured for use in magnitude calculations. important factor influencing the accuracy of locating earthquake epicenters is the accuracy with which arrival times are determined. Particular care was taken to time the seismic-wave arrivals with respect to an accurate common time base and to maintain the quality of timing for the many steps of the data reduction. The internal clock drift during each record change was also accounted for. Time correc- tions were calculated for the arrival times of events that were to be entered into the computer location program. The coding checked before entry into the computer by verifying the consistency of the entries and re-examining the preliminary sheets to verify timing information and number of stations ording the event. equal importance to locating earthquake epicenters is the accuracy of geographic locations of the seismograph stations. The stations were on 1:63,360 maps from which the latitudes, longitudes, and ele- of the stat ions were measured. These data were also entered into the computer program. the procedures described above, the epicenter and hypocenter uncertainty within the microearthquake network is estimated to be approximately 1.2 miles (2 km) with the uncertainty in hypocenter depth ~lightly greater than that for the epicenter location. Model addition to the arrival times and station locations, earthquake ion computations require a crustai velocity model. On the basis of B -7 this model, the seismic ray travel times from hypocenter to each stat are calculated. Velocity models are best derived from the results of large scale sei refraction and reflection studies. Alternatively, because approximate characteristic velocities of most rock types are known, models can estimated on the basis of regional geologic data. This latter method inferior to the former because regional geology models have not been verified beyond depths of a few hundred meters and because the velocity can vary considerably in the various tectonic areas earth. The velocity model used in this study (Table B-2) is a regional model developed by the University of Alaska Geophysical Institute (UAGI) (Biswas, 1980). It is the model presently employed by the UAGI for locating earthquakes in central Alaska. Few detailed crustal studies have been conducted in central Alaska, and little is known of the actual crustal velocity structure. However, the regional velocity model is probably representative of the actual velocity structure in the Talkeetna Terrain and is judged acceptable for use in the location of earthquakes in this study. 8.6 -Location of Microearthquakes All local events (S-P wqve arrivals of approximately 10 seconds or less) located during this study are listed in Appendix D. An event was located by computer if there were arrivals recorded at four or more stations. For this investigation, earthquakes of magnitude (ML) approximately 0.5 to 1.0 or greater were large enough to be recorded at a sufficient number of stations and to be located by computer. Most earthquakes of magnitude less than 0.5 were noted but not located. Figure 9-4 shows the number of earthquakes per day which were located within the microearthquake study area. B - 8 Final earthquake hypocentral locations determined by computer were calculated using the program HYPOELLIPSE (Lee and Lahr, 1979). The inputs to the program are the station locations, velocity model, and the . arrival times of P-and 5-vl/aves from an earthquake recorded by the station network. The origin time, latitude, longitude, and focal depth of an earthquake are calculated from these data. The calculation basically involves the solution of a time versus distance problem; the computer program calculates the four parameters by mathematically minimizing the difference between the observed and computed travel times by the iterative application of a least-squares process. Each observed S or P l't'ave travel time is obtained from the observed station arrival time by subtracting the origin time obtained in the preceding iteration. Each computed travel time is obtained using the crustal velocity model and the epicentral distance based on the station location and the hypocentral location from the preceding iteration. The origin time and hypocentral location of the earthquake are initially fixed to correspond to the P-wave arrival time and to the location of the station having the earliest arrival time. The program compares the residuals of all the stations in the least- square process and adjusts the trial hypocenter and origin time to new values that will reduce the size of the residuals. The calculation of residuals and the adjustment are then repeated until the program com- putes the solution that results in the statistically smallest set of residuals. and this solution is adopted as the origin time and hypocen- tral location of the earthquake. HYPOELLIPSE also performs a statis- tical analysis of hovJ well the final solution fits the data; this 11 fit 11 gives an indication of the quality of the solution. Horizontal and vertical standard errors, in kilometers, of the solution are calculated. B - 9 B.7 -Earthquake Magnitude Determination Procedure A common and accepted parameter for describing the size of earthqu is local magnitude (ML), ~hich is based upon Richter's definition using amplitudes of earthquakes recorded on Wood-Anderson seismographs (Ri ter, 1958). As originally developed and as it has been applied, magnitude scale gives a measure of the seismic energy released duri the earthquake. Earthquakes having magnitudes 1 arger than 5 are often damaging or destructive. Microearthquakes quakes of magnitudes (ML) less than 3. Several methods for determining equivalent Richter magnitudes based on signal duration have been devised, including one that is based on a method used for earthquakes in central California (Lee and others, 1972). The method by Lee and others defines signal duration (coda) as the time from the P-wave arrival to the point where the signal-to-noi ratio is about 5. The equation used to calculate the magnitudes, with coefficients as used in Alaska by Lahr (1979) is: ML = -1.15 + 2 log T + 0.00350 + 0.007H where T is the coda duration (in seconds) measured from the time of the P-arrival to the time when the coda becomes less than 1.0 nm in peak- to-peak amplitude (about five times background noise 1 eve 1), 0 is the epicentral distance to the station in kilometers, and H is focal depth in kilometers. The duration magnitudes have an estimated accuracy of + 1/4 magnitude units. One magnitude value is computed for each stat ion in the network and these are averaged for a final value. Magnitude values are also routinely computed at the UAGI. Their pro- cedure uses amplitude and frequency measurements of the seismic records to determine equivalent Richter magnitudes. The formula used is as follows: B -10 where [ A . WA( f) ] -1 og10 A0 G(f) A is 1/2 the maximum peak-to-peak amplitude on the seismometer trace, in millimeters; f is the frequency of the peak amplitude wave; WA(f) is the gain at frequency f of a Wood-Anderson horizontal torsion seismometer; G(f) is the gain at frequency f of a vertical- component seismometer (non Wood-Anderson) used by UAGI; and A0 is the trace amplitude, in millimeters, for a standard earthquake as a function of the distance from the epicenter. Magnitude estimates for UAGI data are generally considered accurate to within 1/2 (one-half) magnitude unit (Agnew, 1980). B.8 -Focal Mechanisms The pattern of the first ground motions produced by the P-waves of an earthquake recorded at seismograph stations distributed around an epicenter can reveal the orientation of the fault surface upon which the event occurred. Small earthquakes can indicate the same stress field as that of the 1 es s frequent 1 arge earthquakes. Thus, source mechanisms estimated from small earthquakes can be very important for understanding the regional geologic and tectonic environment. To prepare a fault plane solution, the first motions for a particular earthquake are plotted on an equal-area stereographic net. The point representing the angle of emergence of the P-wave as it leaves the B -11 earthquake focus is plotted at the azimuth from the epicenter to recording station. All rays are plotted on a lower hemisphere proj tion. The possible fault planes and principle stress axes are interpreted the first motion plots using the double-couple model of faulting. this model, the maximum and minimum compressive stresses are orthogona and produce orthogonal, conjugate nodal planes. The first moti quadrants formed by the conjugate nodal planes are characterized b alternating areas of compression and dilation, which correspond to u and down ground motion, respectively. The principal stress axes (maxi mum and minimum) 1 ie midway between the orthogonal planes and perpendicular at their line of intersection. First mot ion p 1 ots are usually prepared for sing 1 e earthquakes. ever, to produce a well-defined focal mechanism, enough stations have recorded the earthquake to show a clear pattern. The first motion§ from several earthquakes can be combined to form motion plot. The technique of forming composite first motion and interpreting focal mechanisms depends upon the assumption that the fault orientation and causative stress field remain the same for all the combined earthquakes. 8.9 -Blasting Identification Individual explosions, such as quarry and mine blasts, can be signifi- cant sources of seismic energy (as large as magnitude ML 3 and, at the present state of the art, cannot be positively discriminated from earth- quakes by simple inspection of the signal on the seismogram. However, repetitive blasts at the same location do produce very similar seismo- grams. If done regularly at about the same time, repeated blasting operations can be identified. No blasting sources were identified within the seismograph network for the Susitna Project. B -12 HQUAKE STATION LOCATION TION SUMMARY 1 Elevation Installation Remov a 1 Name Latitude 2 Longitude 2 Meters 2 Date3 Date3 Camp 62°50.2 1 N 148"30.9 1 W 822 20 June 4 July Dam 62"49.8 1 N 148°33.2 1 W 868 25 June 27 Sept. 62"49.8'N 149"19.1'W 650 26 June 27 Sept. Deadman Mt. 63°03.7'N 148°13.6'W 1649 27 June 28 Sept. Jay Creek 62°50.0'N 147"56.9 1 W 1203 27 June 28 Sept. Kosina Creek 62°33.3'N 148°06.6'W 1250 28 June 27 Sept. Mt. 62°36.9'N 148°51.9'W 1119 30 June 25 Aug. Creek 62°56.9'N 148 ° 54 , 5 I~~ 1356 1 July 25 Aug. Chun i 1 na Mt. 62"41.6 1 N 149"36.8 1 W 1192 2 July 26 Sept. Disappointment 62°32.9 1 N 149°27.6'W 1158 4 July 22 Aug. Creek 62°57.5'N 149°33.5'W 1173 4 July 26 Sept. 62°27.45'N 148°45.26'W 1370 22 August 27 Sept. Upper Grebe 62"34.95'N 148"52.89'W 1310 25 August 28 Sept. Swimming Bear 62o52.78'N 148"54.60 1 \11 1155 30 August 28 Sept. Lake Station locations are shown in Figure B-1. Station location and elevation were scaled from 1:63,360 scale base maps on which stations were plotted during installation of the network. Installation and removal dates are for 1980. This was a temporary station installed for calibration purposes. TABLE B-2 VELOCITY MODEL USED FOR 1980 MICROEARTHQUAKE DATA ANALYSIS DeEth (km) 0.0 -24.3 24.4 -40.1 40.2 -75.9 76.0 -300.9 301.0 -544.9 545.0 -deeper Note: 1. Data source is Biswas (1980). Velocity of P-Wave 5.90 7.40 7.90 8.29 10.40 12.60 2. S-wave velocity was determined from P-wave velocity for each layer by assuming Vp/Vs = 1.78. (km/sec) CNL LEGEND Telemetered Station and Radio Transmission Path C. Digital Event Recorder Ill Central Recording Station LYDE CONSULTANTS 1465BA December 1980 0 MICROEARTHOUAKE STATION ARRAY 62.5° 10 20 Mi~s ~~~ 0 10 20 30 Kilometers FIGURE B-1 D "' " 0 3 tr !!l -10 OJ Cl C) c :tJ m OJ "' "0 0 u c 0 .+=' ctl .... (J) (Station moved) (Station moved) (Station moved) ----------------------------- ----(Temporary station) 28 June 1980 1 July 1980 LEGEND Station in operation 1 August 1980 l September 1980 28 September 1980 DAIL V OPERATION SUMMARY OF MICROEARTHOUAKE STATIONS ~L--------------------------~--------------------------------------------------------~ b m U'1 CD )> 0 "' n "' 3 rr !!: ~ <D CD Cl 11 Gl c :0 m to w Station PORTABLE MICROEARTHQUAKE SYSTEM STATION DOCUMENTATION FORM FOR MEQ-800 ------------------------------------Project: ------------------------ ON: time date ----- OFF: time date TC= msec advanced retarded (circle) TC= msec advanced @ -----------retarded (circle) FILTERS: high Hz low Hz -------GAIN: _______________ db RECORD LE~GTH: hours MAX DEFLECTION mm ---------------------------------INTERNAL BATTERIES: A --------------------13 _______ _ OPERATOR ON _____ _ OPERATOR OFF CAL PULSE: __________ rnA.@ db RECORDER COMMENTS Woodward-Clyde Consultants SMOKED PAPER DATA SHEET ~------------------------------------------------------------------------------------------J .b Ol LT1 CD )> 0 "' ' 3 cr ro !0 CD 0 , C) c :0 m m I ~ Time Hr-Min Card --- COMMENTS: L -Local (5-P :":10sec.) R-Regional (S-P;-1Qsec.) T -Teleseism B -Blast TR -Trace ? Questionable event PROJECT Remarks-Location Comments FORI'l 21 REV. 1-9/2lj/79 CARD: yes no STATION READINGS: I -readable, impulsive E -readable, emergent X -not readable STATIONS __ _j___J I ~I an READ BY , ________ ..:;.:::c::.::..:. __ _ REVIEWED BY date; ±j - I -- I MICR.OEARlfHOUAKE PRELIMINARY READING SHEElf APPENDIX C -HISTORICAL EARTHQUAKE CATALOG This appendix lists instrumentally recorded earthquakes of (a) magnitude 4.0 or greater (includes all magnitude scales) or (b) intensity V or greater; the earthquakes are taken from the National Oceanic and Atmospheric Administration (NOAA) earthquake catalog within the follow- ing boundaries: North boundary -64°N Latitude South boundary-6loN Latitude East boundary -l46.5°W Longitude West boundary -l52°W Longitude The earthquakes in the catalog are shown in Figures 4-4, 4-5, and 4-6. The explanation for the catalog headings in Table C-1 is as follows: DATE Date the earthquake occurred, in day, month, year, ac- cording to the origin time in Universal Coordinated Time ( UCT). TIME -Origin time of the earthquake, in hours, minutes, and sec- onds in Universal Coordinated Time (UCT). LAT, LONG North latitude and west longitude of epicenter in degrees. INTEN -Modified Mercalli Intensity of the event from felt reports. MAG -Magnitude of the earthquake. c -1 ---------"F SM -Type of magnitude determination. N1 -Magnitude is obtained from the source given in comments MB -Body-wave magnitude (Mb) MS -Surface-wave magnitude (Ms) DIS -Not used. H -Depth of earthquake (focal depth) in kilometers. S -Source of location and magnitude values. c -2 27 AUG 1904 21 :56:06 0 64.000N "151.000W VI 8. 30N' REPORTED DAMAGE ...... HYPOCENTER DEPTII ASSIGNED U1 ORIGUIAI· DATA SOURCE = GUT -I 0 I'IAGNITUDE(FRJI.CTIONAL NOTATION,AVE)=B.30, AUTHORITY-PAS ;o ...... n n I 2 31 JAN 1912 20: 11 :18.0 61 .OOON 147.500W 7. 25N' 80 N REPORTED FELT INFORMATION :;1::> ..... ORIGINAL DATA SOURCE G R r MAGNITUDE(FRACTIONAL NOTATION,AVE)=7.25, AUTHORITY-DAS rn :;1::> ;o 3 7 JUL 1912 07:57:42.0 64.000N 147.000W 7. 'lON' N REPORTED FELT INFORMATION -t ::r:: ORIGINnL DATA SOURCE G R .0 MAGNITUDE(FRJI.C~IONAL NOTATION,AVE)=7.10, AUTHORITY-DAS c ):> ;;:><; 4 17 JUL 1923 01:02:11.0 63.000N 147.000W 5. 60N' N ORIGINAL DATA SOURCE = GUT rn MAGNITUDE(FRAC~IONAL NOTATION,AVE)=5.60, AUTHORITY-PAS n ):> -t 5 24 FEB 1925 13:15:00.0 61 .SOON 119.000W v z N REPORTED FELT INFORMATION ):> ORIGINAL DATA SOURCE = EQH r 0 NON-INSTRUMENTAL Gl 6 21 JAN 1929 10:30:53.0 64.000N 14S.OOOW 6. 25N' N REPORTED FELT INFORI11\TION ORIGINAL DATA SOURCE = GUT MAGNITUDE(FRACTIONAL NOTATION,AVE)=6.25, AUTHORITY-PAS 7 3 JUL 1929 00:53:00.0 62.500N 149.000W 6.25N' N ORIGINnL DATA SOURCE = GUT MAG~ITUDE(FRACTIONAL NOTATION,AVE)=6.25, AUTHORITY-PAS a 4 JUL 1929 04:28:35.0 64.000N 14B.OOOW 6.50N' N ORIGINAL DATA SOURCE GUT MAGNITUDE(FRAC~IONAL NOTATION,AVE)=6.50, AUTHORITY-PAS 9 29 MAY 1931 05:16:32.0 63.000N 149.000W 5. 60N' N ORIGINAL DATA SOURCE GUT MAG~ITUDE(FRACTIONAL NOTATION,AVE)=5.60, AUTHORITY-PAS 10 17 OCT 1931 12:34:50.0 63.000N 147.000W v 5.60N' N REPORTED FELT INFORMATION ORIGINAL DATA SOURCE = GUT MAGNITUDE(FRACTIONAL NOTATION,AVE)=5.60, AUTHORITY-PAS 1 1 14 SEP 1932 08:43:23.0 61 .OOON 14B.OOOW v 6. 25N' 50 N REPORTED FELT INFORMATION ORIGINAL DATA SOURCE GUT MAGNITUDE(FRACTIONAL NOTATION,AVE)=6.25, AUTHORITY-PAS 12 4 JAN 1933 03:59:28.0 61 .OOON 148.000W VI 6.25N' N REPORTED DAMAGE ORIGINAL DATA SOURCE = GUT MAGNITUDE(FRACTIONAL NOTATION,AVE)=6.25, AUTHORITY-PAS 1 3 4 JAN 1 933 04:00:00.0 61 .OOON 147.000W VI N REPORTED FELT INFORMATION ORIGINAL DATA SOURCE USE 1 4 27 APR 1933 02:36:00.0 62.000N 151.000W VI N REPORTED DAMAGE ORIGINAL DliTA SOURCE USE WOODWARD-CLYDE CONSULTANTS Pl\GE 2 cn·r. DATE TIME(GM'r) LllT LONG BL IN'l'EN MAG S1'1 H DIS Q S LOCA'riON A N D C 0 M M E N T S NO. DAY-MO-YEliR HR-MIN·-SEC (Ml'l) (KM)(KM) ----------------------------------------------------------------------------------- 15 27 APR 1933 02:36:0<1.0 61 .250N 150.750W VII 7. OON' N REPORTED FELT INFORMATION -1 ):> ORIGINAL DATA SOURCE = GUT ro l'IAGNITUDE(FRACTIONI\L NOTATION ,AVE )=7. 00, AUTHORITY-PAS I rr1 16 12 JUN 1933 15:23:36.0 61 .SOON 150.500W 5.60N' N REPORTED FELT INFORMATION n I ORIGINAL DATA SOURCE = GUT ,_. MAGNITUDE(FRACTIONAL NOTATION,AVE)=5.60, AUTHORITY-PAS n 17 13 JUN 1933 22:19:47.0 61.000N 15I.OOOW 6. 25N' N REPORTED FELT INFORMATION 0 ::z: ORIGINAL DA'rA SOURCE "" GUT -1 ~ NAGNITUDE(FRhCTIONAL NOTATION,AVE)=6.25, AUTHORITY-PAS :z c: rr1 18 19 JUN "l933 18:47:43.0 61 . 250N 150.500W 6. DON' N REPORTED FELT INFORMATION 0 ORIGINAL DATA SOURCE = GIJT MAGNITUDE( FRACTIONAL NOTATION,AVE)=6.00, AUTHORITY-PAS 19 26 JUL 1933 04:57:26.0 63.000N 147.000W 5.60N' N ORIGINAL DATA SOURCE = GUT MAG~ITUDE(FRACTIONAL NOTATION,AVE)=5.60, AUTHORITY-PAS 20 4 MAY 1934 04:36:00.0 61 .OOON 148.000W VI N REPORTED DAMAGE ORIGINAL Dl\TA SOURCE USE 21 4 MAY 1934 04:36:07.0 61 .250N 147.500W VI 7.20N' so N REPORTED DAMAGE ORIGINAL DATA SOURCE = GUT MAGNITUDE(FRACTIONAL NOTATION,AVE)=7.20, AUTHORITY-PAS 22 2 JUN 1934 16:45:29.0 61 .250N 147.000W 6. 25N' N ORIGINAL DATA SOURCE = GUT MAGNITUDE(FRl\C~IONAL NOTATION,AVE)=6.25, AUTHORITY-PAS 23 2 AUG 1934 07:13:00.0 62.000N 14B.OOOW v N REPORTED FELT INFORI'IATION ORIGINAL DATA SOURCE = USE 24 2 AUG 1934 07:13:08.0 61 .500N 147.500W v 6.00N' N REPORTED FELT INFORMATION ORIGINAL Dli'l'A SOURCE '-""' GUT Ml\GNITUDE(FRAC~IONAL NOTATION,AVE)=6.00, AUTHORITY-PAS 25 18 JAN 1936 01:20:00.0 62.000N 152.000W 5. 60N' N ORIGINAL DATA SOURCE = GUT MAGNITUDE(FRACTIONAL NOTATION,AVE)=5.60, AUTHORITY-PAS 26 23 OCT 1936 06:24:24.0 61 .400N 149.700W VI N REPORTED DAMAGE ORIGINAL DATA SOURCE = CGS 27 24 OCT 1937 11 : 36: 1 2. 0 61 .OOON 147.000W v N REPORTED FELT INFORMATION ORIGINAL DATA SOURCE CGS 28 30 JUL 1941 01:51:21.0 61 .OOON 151.000W VI 6. 25N' N DAMAGE DATA. SOURCE GOT (FRACTIONAL l'I0Tl\TION, AVE)=6. 25, 30 3 NOV 19<13 14:32:30.0 62.000N 151.000W v 31 19 AUG 191!8 13:50:46.0 63.000N 150.500\i/ 6.25N' 100 N QUl\LITBDB n ORIGINAL DATA SOURCE = GUT 0 MAGI:UTJ.:DE( FRACTIONAL NOTATION ,AVE)=6. 25, AUTHORITY-PAS :z: -i 32 25 JUN 1951 16: 12:37.0 61 .I DON 150.100W v 6. 25N' 128 N REPOR'I'ED FELT INFORMATION :z c::: ORIGINAL DATA SOURCE = ISS fTl Ml\GNITUDE(FRACTIONAL NOTATION,AVE)=6.25, AUTHORITY-PAS CJ 33 3 MJ\R 1954 20:1!6:07.0 61. SOON 146.500W v GO N REPORTED FELT INFORMATION .ORIGINAL DATA SOURCE = USE 34 23 AUG 1954 14:57:34.0 61. OOON 149.500W v N REPORTED FELT INFORMATION· ORIGINAL DA1'A SOURCE = USE 35 9 JUN 1956 02:26:57.0 64.000N 148. ooow v N REPORTED FELT INFORMATION ORIGINAL DATA SOURCE = USE 36 3 JAN 1960 11:38:30.0 61 .OOON 152.000\i/ v N REPORTED FELT INFORMATION ORIGINAL DATA SOURCE = CGS 37 10 MAR 1960 00:21!:20.0 64.000N 149.000W v N REPORTED FEL'I' INFORMATION ORIGINAL DATA SOURCE = CGS 38 1 0 MJ\Y 1962 00:03:1!0.2 62.000N 150.1 oow v 6. OON' 72 N REPORTED FELT INFORMATION 020 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = ccs Ml\GNITUDE(FRl\CTIONAL NOTATION,AVE)=6.00, AUTHORITY-BRK 39 29 JUN 1962 16:28:07.1 62.400N 152.000W IV 4. 75N' 50 N REPORTED FELT INFORMATION ORIGINl\L DATA SOURCE CGS MAGNITUDE(FRAC~IONAL NOTATION,AVE)=4.75, AUTHORITY-BRK 40 21 OCT 1962 02:05:22.7 61 .lOON 149.700W VI 80 N REPORTED DAMAGE 037 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE CGS 1!1 13 DEC 1962 14:57:27.9 61. <lOON 147.200W v 69 N REPORTED FELT INFORMATION 0 1 3 P 1\ND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATl\ SOURCE = CGS 1!2 6 APR 1963 11:19:23.2 63.400N 149.600W 5.30MB 42 N 077 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 113 6 APR 1963 12:07:08.2 63.GOON 149.700W S.OOMB 49 N 038 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATl\ SOURCE = CGS WOODWARD-CLYDE CONSULTANTS Pl\GE 4 Cl\T. Dl\TE TIME(GMT) LJIT LONG SL IN'l'EN 1'11\G SM H DIS Q S L 0 C A T I 0 N A N D C 0 1'1 M E N T S NO. D1\Y-MO-YE1\R HR-MIN-5EC (MM) (KM)(KM) --------------------------------------------------------------------------------------------------------------------------------~-----j ::P 14 2 MAY 1963 23: 13:09.4 63.100N 149.900W 6.1 OMB 79 N 019 P AND/OR P' ARRIVALS USED IN co HYPOCENTER SOLUTION r ORIGINl\L DA'l'A SOURCE CGS f"Tl ("") 45 1 1 JUN 1963 1 3; 08; 31 . 5 63. 2DON 151.4DOW 5.10MB 36 N 054 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTiutl I .__. ORIGINAL DATA SOURCE = CGS ("") 16 2 JUL 1963 02:52:55.8 6.tJ.OOON 148.400\11 4.00MB 33 N 005 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION 0 z ORIGINAL DATA SOURCE = CGS -j ...... 17 22 AUG 1963 03:58:43.2 63.200N 148.500\11 4.60MB 1 01 N 014 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION z c. ORIGINAL DATA SOURCE = CGS rn CJ 48 3 SEP 1963 12:59:52.3 61.900N 1 50. iJOOW 4.00MB 116 N 007 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE CGS 49 22 SEI> 1963 20:33:47.7 62.900N 148.800W <L OOMB 53 N 006 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 50 18 OCT 1963 08:05:22.1 62.600N 1.;16.600W <1.20MB 51 N REPORTED FELT INFORMATION 011 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE CGS 51 19 OCT 1963 11:19:31.8 62.400N 149.600W 4.30MB 96 N 009 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 52 22 NOV 1963 20:10:40.1 63.400N 150. ooow .tJ.10MD 156 N 006 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 53 24 NOV 1963 17:48:47.0 61.BOON 149.50 0W 4.30MB 36 N 009 P llliD/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 54 14 DEC 1963 07:51:07.9 62.700N 149.50DW 5.1 OMB 95 N 025 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 55 5 JAN 1964 01:31:27.0 61 .900N 1 49. 50fJW 4.60MB 72 N 01 1 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGIN1\L DATA SOURCE = CGS 56 28 JAN 1964 18:30:43.9 61 .20DN 147.800W 4.00MB 172 N 007 P AND/OR P' ARRIV1\LS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 57 31 JAN 1964 04:17: 12.4 61 .SOON 151.9DOW 4.9DMB 33 N 038 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE CGS 58 7 l'lAR 1964 23:06:27.7 61 .600N 151.40DW 4.40MB 72 N 008 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTIOH ORIGINAL DATA SOURCE = ccs 59 22 1'11\R 1964 06:22:15.1 61 .300N l47.8DOW 4.501'1B 62 N SEICHE ASSOCIATED WITH EARTHQUAKE REPORTED CASUALTIES HY~~NTER SOLUTION DEPTH RESTRAINED BY GEOPHYSICIST 181 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION MORE ACCURl\.TE SOLUTION BASED ON DETAILED LOCAL DATA ORIGINliL DA'l'A SOURCE = CGS ISOSEISMAL MAP PUBLISHED BY USE (""") MAGNITUDE = 8. 3 USING NOAA AVERAGE l'lS ( DISPEI FORI'IULA) 0 z l'lliGNITUDE(FRl\.CTIONAL NOTATION,AVE)=8.50, AUTHORITY-PAS -1 ....... z 61 28 i'IAR 1964 09:26:16.5 61 .300N 148.800W <1.40MB 33 N 013 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION c ORIGINAL DATA SOURCE = CGS rn 0 62 28 i'IAR 1964 13:54:19.9 62.100N 147.100W <1.60MB 15 N o·15 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 63 28 MAR 1964 15:27:30.1 6l.OOON 149.000W 4.70MB 33 N 010 P AND/OR P' ARRIVALS l)SED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 64 28 MAR 1964 19:21 :38.8 61 .600N 146.700W 4.60MB 45 N 019 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 65 29 MAR 1964 23:40:54.8 61.1 OON 15l.OOOW 4.70MB 25 N 020 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 66 30 MAR 1964 03:35:12.0 61 .200N 151.100W 4.40MB 30 N 007 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 67 30 MAR 196'.1 10:47:05.9 61 .500N 146.800W <1.30MB 35 N 009 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 68 30 MAR 1964 11:35:18.8 61 .500N 147.900W 4.40MB 25 N 015 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 69 30 i'IAR 1964 17:41:13.4 61 .500N 150.000W 4.30MB 40 N 017 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 70 3 APR 1964 22:33:42.2 61 .600N 147.600W v 5.70MB 40 N REPORTED DAMAGE 080 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS MAGNITUDE( FRACTIONAL NOTATION ,AVE)=6. 00, AUTHORITY-PAS 71 7 APR 1964 03:53:57.2 61.1 DON 148.700W 4.20l'ID 33 N 011 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 72 12 APR 1964 14:35:39.2 61.200N 151 .lOOW IV 5.00MB 28 N REPORTED FELT INFORMATION 041 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 73 13 APR 1964 17:43:26.3 61 .lOON 147.400W 4.40MB 35 N 011 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS WOODWARD-CLYDE CONSULTANTS Pl\GE 6 CAT. DATE TII'!E(GJ'IT) IJ\T LONG SL INTEN RAG Sl'l H DIS Q S L 0 C A T I 0 N A N D C 0 1'1 1'1 E N T S NO. Dl\Y-MO-YEAR HR-MIN-SEC (l'tM) ( Kl'l) ( KM) ------------------------------------------------------------------------------------------------------------------------------------ ---i 74 13 APR 1964 23:48:52.7 61 .OOON 1t.l9.300W 4.1 OMB 33 N 009 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION )::> ORIGINAL DATA SOURCE = CGS OJ I rn 75 14 APR 1964 07:59:25.4 61.400N 147.000W 4.40HB 33 N 018 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION n ORIGINAL DATA SOURCE ; CGS I 1-' 76 14 APR 1964 1 5:55: 1 0. 9 61 .300N 1.;17. 300W 5.40iill 30 N 051 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION n ORIGINAL DATA SOURCE = CGS C) ::z 77 1964 16:59:30.1 61 .400N 150.800W 5.10l4B 35 N 036 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ---i 14 APR ,__. ORIGINAL DATA SOURCE ; CGS :z c= rn 78 14 APR 1964 21:33:37.3 61.000N 147. 3001<1 4.2011B .:!0 N 014 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION 0 ORIGINAL DATA SOURCE = CGS 79 16 APR 1964 14:31:16.3 61.400N 149.200W 4.60HB 33 N 015 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 80 17 APR 1964 07:26:39.0 61.100N 149. •JOOW 4.40MB 33 N 007 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 81 20 APR 1964 11 :56:41 . 6 61 .400N 1 -G7. 300W 5.70i'ill 30 N REPORTED FELT INFORMATION 087 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = ccs I'U\GtliTUDE(FRACTIONlU. NOTATION ,AVE)=6. 50, AUTHORITY-PAS 82 20 APR 196<\1. 15:40:28.0 61.500N 147.300W S.OO.Iffi 30 N 029 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 03 20 );I.PR 196<;1 16:49:41 .B 61 .400N 147.300W 4.20t'IB 33 N 009 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 84 21 APR 1964 05:01:35.7 61 .500N 14!7.400W 5.4011B 40 N REPORTED FELT INFORMATION 066 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS MAGNITUDE(FRACTIONAL NOTATION,AVE)=6.00, AUTHORITY-PAS 85 30 APR 196<.1 11:50:47.\1 61.300N J.\17. OOOI<il 4.iJOI1B 33 N 015 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 86 9 MAY 196<:! 21:06:12.2 61.700N 152.000\1! 5.00MB 25 N 010 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 87 20 MY 196<;1 01 :55:23.8 61.300W 148.300W 4.00MB 33 N 006 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = ccs 88 5 JUN 1964 11 :50:24.9 63.100N 151.100\<l IJ.20im 94 lN 006 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 89 16 JUN 1 S64 10:23:39.1 61 .200N 146.8001>~ 4.50Hfl (!() JliJ -----------------------------------------------------------------------------------------------------------------------------------· ~ -\ ~ 009 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION co 90 22 JUN 1964 08:32:02.1 62.1 OON 148.500W -1.10MB 33 N I ORIGINAL DATA SOURCE = CGS rn ("""} 91 26 JUN 1964 05:28:49.0 61 .700N 148.300W 4.30MB 33 N 011 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION I 1-' ORIGINAL DATA SOURCE = CGS 92 29 JUN 1964 07:21:32.8 62.700N 152.000W 5.60MB 33 N REPORTED FELT INFORMATION ("""} C> 058 P AND/OR P' ARRIVALS USED IN HYPOl."'ENTER SOLUTION :z -\ ORIGINAL DATA SOURCE = CGS ....... :z c 93 27 JUL 1964 15:53:23.6 63.400N 148.500W 4.20MB 115 N 008 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION rn ORIGINAL DATA SOURCE = CGS 0 94 16 AUG 1964 02:57:05.6 61 .600N 150.200W 4.10MB 63 N 008 P.AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 95 16 AUG 1964 12:38:20.6 62.1 OON 147.300W 4.10MB 56 N 005 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 96 20 AUG 1964 14:03:34.4 61 .400N 147.500W 4.30MB 35 N 008 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 97 24 AUG 1964 01:36:23.7 61 .200N 146.800W 4.00MB 47 N 007 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 98 27 AUG 1964 10:31 :59.7 63.600N 148.200W 4.20MB 106 N 008 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 99 6 SEP 1964 17:36:44.3 63.1 OON 147.700W 4.80MB 33 N 013 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 100 23 SEP 1964 16:37:19.1 61 .600N 150.000W 4.10MB 33 N REPORTED FELT INFORMATION 005 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 101 28 SEP 1964 18:30:20.2 61 .OOON 147.400W 4.50MB 89 N 013 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 102 3 OCT 1964 13:39:39.9 61 .400N 147.100W 5.20HB 48 N 039 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 103 20 NOV 1964 21:27:39.5 63.700N 146.500W 4.60MB 80 N REPORTED FELT INFORMATION 012 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 104 27 NOV 1964 07:47:07.6 62.600N 151 .500W IV 5.40MB 113 N REPORTED FELT INFORMATION 023 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE CGS MAGNITUDE(FRACTIONAL NOTATION,AVE)=4.63, AUTHORITY-BRK WOODWARD-CLYDE CONSULTANTS """"' ----~~ ... ~-~·····~----·-·---~---...... ········--···-·~~~---------~""""'--- PZ\GE 8 Cl\T. Dl'ITE TIME(GMT) L11T LONG £L INTEN i'l1\G SM H DIS Q S L 0 C A T I 0 N A N D C 0 1'1 M E N T S NO. DAY-MO-YEJ\R HR-IUN-SEC (11.M) (KI'i)(KI'I) ----------------------------------------------------------------------~-----~~------------------------------------------------------- 105 21 DEc 1964 18:32:03.0 63.1 DON 150.300W ~.ElOlm 11 1 N 018 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION -I )::> ORIGINAL DATA SOURCE = CGS o:J I fTl 106 Jl\N 1965 20:02:38.0 61 .7DO!N 148.9DOW 4.30i'ffi 33 N 008 P AND/OR l?' ARRIVALS USED IN HYPOCENTER SOLUTION 0 ORIGINAL DATA SOURCE = CGS I ,_. 107 11 JAN 1965 16:57:27.0 61.100W 151.000W 5.lJO!Im 59 N 022 P AND/OR P' ARRIVALS USED IN HYPOCEN'rER SOLUTION ORIGINAL DATA SOURCE = CGS " 0 z 108 8 FEB 1965 03:31:34.8 63.400N 151.700!.-1 4.50I'IB 31 N 011 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION -I ...... ORIGINAL DATA SOURCE = CGS z c. rn 109 25 FEB 1965 02:02:37.4 61 .;wow 146.700W 4.50i'ffi 40 N 015 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION CJ ORIGINAL DATA SOURCE = CGS 11 0 MR 1965 13:56:07.4 61 .700N 147.700W 4.00MB 43 N 010 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 11 1 8 MAR , 965 12:04:21 . 0 62.50011il 150. 4\00W 4.50i'IB 104 N 016 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DAT~ SOURCE = CGS 112 10 MAR 1965 20:29:34.5 62.500N 1 ~~-300\~ 4.80HE 85 N 017 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE CGS 113 19 APR 1 965 07:15:54.4 62. lOON 1 so. ;wo~-J 4.1 OMB 83 N 014 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL D~TA SOURCE = CGS 11 4 9 MAY 1965 14:27: 1 s. 6 6J.200N 149.200W 4.00NB 11 , N 010 P AND/OR P' ~RRIVALS USED IN HYPOCENTER SOLU'l'ION ORIGINAL DATA SOURCE = CGS 115 1 , MAY 1965 11:31:36.3 61.<\WON 149.600!.1 IV S.SOI"iB 58 N REPORTED FELT INFORMATION 015 P Mm/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS AAGNITUDE(FRACTIONAL NOTATION,AVE)=5.75, AUTHORITY-PAS 116 2 JUN 1965 00:43:04.3 62.100N 151 . <lODW 4.50l'ID 24 N 016 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 117 26 JUN , 965 23:13:1,12.4 62.800N 149.100W 4.001'ID 75 N 020 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS .11 B 20 JUL , 965 16:57:00.2 62.000N Hl7. ooow 4. OOt1B 33 N 010 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLU'l'ION ORIGINAL DATA SOURCE = CGS 119 7 AUG 1965 21:14:43.6 61.900N 151 .ooow 4.801'113 80 N 030 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 120 8 AUG 1965 11:28:21.9 61.200N 1 IJ9. 300W 4.10l'ffi 86 N 007 P 11ND/OR l?' ARRIVALS. USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 121 13 AUG 1965 15:19:17.2 61 .200N 151 .400W 4.201'ffi 92 N 019 P AND/OR .P' .ARRIVALS USED ORIGINAL DATA SOURCE = CGS 122 16 OCT 1965 11:45:25.7 63.1 OON 150.300W 4.60l'IB 84 N 014 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 123 27 OCT 1965 12:47:28.3 6l.OOON 146.500W 4.00tffi 1 N 014 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION n ORIGINAL DATA SOURCE = CGS 0 :z -1 121! 24 NOV 1965 08:22:39.0 63.200N 150.900W 5.00MB 129 N REPORTED FELT INFORMATION ...... 037 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION :z c::: ORIGINAL DATA SOURCE = CGS I'Tl I'IAGNITUDE(FRACTIONAL NOTATION ,AVE)=4 ,IJQ, AUTHORITY-BRK 0 125 HI DEC 1965 17:54:57.4 63.600N 150.000W 4.00MB 11 3 N 009 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 126 24 DEC 1965 16:10:01.1 62.400N 149.700W t.l.20MB 95 l'l 008 P AND/OR P' ARRIVALS USED. IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 127 18 JAN 1966 21 :29:51 • 5 61.MON 151.900W 1. lOI'lB 80 N REPORTED FELT INFORMATION 011 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 128 18 JAN 1966 21 :46:01 .5 61.500N 150.700W 4. 1 ONE! 69 N REPORTED FELT INFORMATION 011 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 129 24 JAN 1966 11:41:25.1 62.600N 151 .600W 4.20MB 41 N 010 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 130 3 i'IAR 1966 17:37:03.7 61 .400N 150.600W il.OO.MB 53 N REPORTED FELT INFORMATION 010 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 1 31 19 I'IAR 1966 09:33:43.8 62.<lOON 15l.:wow 4.30MB 86 N 018 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 132 22 MAR 1966 10:28:59.9 61.200N 151 .&OOW 4.20MB 103 N 019 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS ·133 25 MAR 1966 01:15:11.8 62.600N 151 .ooow <1.40MB 106 N 005 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 13.:1 11 APR 1966 18:49:57.3 63.800N 151.400W 4. 1OMB 47 N 007 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE CGS 1 35 11 MY 1966 01:26:213.3 62.800N 150.1 oow 4.60f'l.B 99 N 023 P AND/OR P' ARRIVALS USED ,IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS WOODWARD-CLYDE CONSULTANTS Pl\GE 10 CI\T. DATE TIME( GMT) U\T LONG SL INTEN Mli.G SM H DIS Q S LOCATION AND C 0 1'1 M E N T S NO. DAY-MO-YEAR HR-I'IIN-SEC (MM) ( KM)( KM) ------------------------------------------------------------~-------------------------------------------------~--------------------~- 151.400W --; \36 19 JUN 1966 12:56:14.3 63.300N 4.301'1B 1 36 N 012 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION p ORIGINAL DATA SOURCE = CGS OJ r rn 1 37 22 JUN 1966 11 :38:50.7 61.300N 147.700W 5.20MB 28 N REPORTED FELT INFORMATION (""") 073 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION I ORIGINAL DATA SOURCE = CGS ...... MAGNITUDE(FRACTIONAL NOTATION,AVE)=5.13, AUTHORITY-PAL (""") 0 138 17 JUL 1966 08:46:27.7 62.000N 151 .900W 4.50MB 119 N 041 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION :z ORIGINAL DATA SOURCE = CGS --; ...... :z 1 39 30 AUG 1966 20:20:53.9 61 .lOON 147.500W v 5.80PlB 35 N REPORTED FELT INFORMATION c rn 143 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION 0 ORIGINAL DATA SOURCE = CGS ftAGNITUDE(FRACTIONAL NOTATION,AVE)=5.88, A1.1I'HORITY-PAS 140 30 AUG 1966 20:23:18.2 61.500N 147.500W v 5.50PlB 33 N REPORTED FELT INFORMATION 019 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS i'U\GNITUDE(FRACTIONAL NOTATION ,AVE)=5. 00, AUTHORITY-BRK 141 31 AUG 1966 14:10:43.9 64.000N 146.800W 4. 1 OI'IB 28 N 012 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 142 SEP 1966 23:19:08.1 61 .700N 149.700W 5.1 Ol'IB 63 N REPORTED FELT INFORMATION 079 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 143 9 SEP 1966 12:24:03.3 61.400N 146.900W 4.00MB 33 N 016 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 144 9 SEP 1966 15:36:57.3 61 .400N 147.BOOW 4.40MB 58 N 015 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 145 7 OCT 1966 20:55:56.4 61.700N 150.\00W 5.60MB 57 N REPORTED FELT INFORMATION 115 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 146 11 OCT 1966 16:49:49.2 62.600N 148.BOOW 4.201'1B 54 N 015 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 147 11 DEC 1966 19:22:00.6 62.700N 150.900W 4. 1 OPlB 70 N 006 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 148 16 DEC 1966 21:59:46.2 61 .400N 149.500W 4.1 OMB 53 N REPORTED FELT INFORMATION 012 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 1.:19 13 JAN 1967 09:37:55.9 150 19 JAN 1967 19:38:56.7 IN THIS IS A LESS RELIABLE CGS 151 14 FEB 1967 08:12:52.3 63.B79N 151 .126W 4.00fffi 46 * N 006 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION NOAA FEELS THIS IS A LESS RELIABLE SOLUTION ORIGINAL DATA SOURCE CGS n 0 z 1 52 16 FEB 1967 07:41:38.7 62.381N 151,338W 4.10lffi 81 N REPORTED FELT INFORMnTION --t 011 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION z ORIGINAL DATA SOURCE = CGS c:: ITI CJ 153 Ml'IR 1967 11 :51 : 34. 7 63.047N 151. 264W 4.00MB 127 N 014 P.AND/OR P' ARRIVALS US~D IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 1 154 31 1'11\R 1967 04:18:31.3 63. 124N 148.495W 4.50tm 82 N REPORTED FELT INFORMATION 033 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 155 3 APR 1967 02:53:46.4 62.611N 150.916W 4.20.1'1B 105 N 011 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DnTA SOURCE = CGS 1 56 9 APR 1967 12:52:05.3 61. 620N 1 51 . 380W 4.20fffi 54 N 012 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 157 10 APR 1967 1<1:44:26.8 63.008N 148.797W 4.00MB 72 N 015 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 158 5 MAY 1967 1 7:06: 1 5. 3 63.713N 148.451W 5.00MB 103 N REPORTED FELT INFORMATION 087 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 159 14 JUN 1967 20:45:4.:1.7 62.500N 149.200\il 4.10MB 86 N 013 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 1 60 6 JUL 1967 05:06:13.4 62.400N 147. 400W III 5.10NB 59 N REPORTED FELT INFORMATION 072 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = USE 161 12 JUL 1967 15:15:37.9 62.700N 149.500W 4.10Mil 78 N 016 P AND/OR P' ARRIVI\LS USED IN HYPOCENTER SOLUTION ORIGINAL DnTA SOURCE = CGS 162 1 8 AUG 1967 05:50:29.0 61 .sOON 151 .ooow 4.50l'ID 19 N REPORTED FELT INFORMATION 043 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = USE 163 1 1 OCT 1967 07:56:36.1 63.000N 151.100W 4.60MB 115 N REPORTED FELT INFORMATION 023 P AND/OR P' ARRIVI\LS USED IN HYPOCENTER SOLUTION ORIGINAL Dl\TA SOURCE = IJSE WOODWARD-CLYDE CONSULTANTS PTIGE 1 2 GAT. DTITE TIME(GMT) LTIT LONG SL INTEN MAG SM H DIS 0 S L 0 C A T I 0 N A N D COMMENTS NO. DTIY-MO-YETIR HH-MIN-SEC (MM) ( KM) ( KM) -I ----------------------------------------------------·-------------------------------------------------------------------------------· J;> co 164 10 NOV 1967 18:29:57.3 62.300N I 51 . 400W 4.90MB 90 N 041 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION I rr1 ORIGINAL DTITA SOURCE CGS (""""} I 165 14 NOV 1967 1)0:22:10.0 61. SOON 1.51 . 800W 4.00MB 3 =~ N 009 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ...... ORIGINTIL DATA SOURCE = CGS (""""} 166 22 NOV 1967 02:14:26.3 63.600N 147 .:wow 4.30MB 2 N 029 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION 0 z ORIGINAL DATA SOURCE = CGS -I 1-1 z 167 4 DEC 1967 08:19:08.5 62.400N 151.800W 4.90MB 96 N 028 P AND/OR P' ARRIVALS USED IN HYPOCENTER SO LOTION c rr1 ORIGINAL DTITA SOURCE = CGS CJ )68 1 0 DEC 1967 03:13:34.8 61.400N 147.400W 4.20MB 30 N 010 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 169 21 MTIR 1968 11:33:24.3 62.400N l50.600W 4.10MB 72 N 02! P AND/OR P' TIRRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DliTA SOURCE = CGS 170 8 APR 1968 03:32:48.4 61.500N 147.800W 4.20MB 4B N 025 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DTITA SOURCE CGS 171 30 APR 1968 17:39:40.2 62.000N 151.100W 4.00MB 78 N 016 P liND/OR P' ARRIVTILS USED IN HYPOCENTER SOLUTION ORIGINAL DTITA SOURCE = CGS 172 18 MTIY 1968 06:50:27.4 61. 200N 147.600W 4.30MB 33 N REPORTED FELT INFORMATION HYPOCENTER SOLUTION HELD AT 33 KM (NORMAL DEPTH) 014 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLU'fiQN ORIGINTIL DliTA SOURCE = USE 173 29 MAY 1968 15:25:39.0 62.300N 149.IOOW 4.00MB 51 N REPORTED FELT INFORMATION 013 P AND/OR P' TIRRIVALS USED IN HYPOCEN'rER SOLUTION ORIGINAL DATA sOURCE = USE 174 15 JUN 1968 !3:38:06.5 G1 .CIOON 146.900W 4.90MB 19 N REPORTED FELT INFORMATION 038 P AND/OR P' AHRlVALS USED IN HYPOCENTER SOLUTION ORII;INAL DATA SOURCE = USE 175 7 JUL 1968 01:10:29.5 61. 2S2N 147.289W 4.80MB 14 N 019 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 176 3 AUG 1968 07:51:13.1 G1. 754N 151.349W 4.10MB 60 N 014 P liND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAl, DATA SOURCE = CGS 177 31 AUG 1968 17:47:06.9 61. 734N 150.9llW 4. lOMB GG N 013 F AND/OR P' TIRRJVALS USED IN HYPOCENTF:R SOLUTION ORIGINAL DATA SOURCE = CGS 178 22 SEP 1968 (l(i : ) 3 : 56 . 6 G1.184N 150.729'-1 IJ.OOM!I 51 N l\HRIVAI,S USED IN HYPOCENTER SOLU'riON ,.79 4 OCT 1968 1 6: 27: 24 . '3. HlO 7 OGT 1968 18:54:53.6 61 .400N 150.30UW IV 4.20MB 55 N REPORTED FELT INFORMATION 016 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = USE 1 B 1 28 DEC 1960 0(1:15:55.0 63.000N 148.200W IJ.60MB ao N REPORTED FELT INFORMATION 021 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE USE 182 ::19 DEC 1968 20:57:07.9 62.980N '151.014W .a.oorm 139 N 010 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS lf.ll 31 l-IAR 1969 11:44:20.0 63.611N Hl7.601W 4.101'19 93 N 011 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE CGS 184 <I MY 1969 09:20:00.1 63.549N 148.697W 4.20MB 33 N HYPOCENTER SOLUTION HELD AT 33 KM (NORMAL DEPTH) 'l19 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 185 10 mi.Y 1969 21:16:04.1 62.S91N 151 . 1 .:!3W <J. omm 11'1 N 011 P AND/OR !?' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 185 9 JUN 1969 08:02:11.2 62.<100N 149.000W 41.101'ID 5~ N REPORTED FELT INFORMATION 022 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = USE 187 17 JUL 1969 22:03:36.7 63.97BN 147.480W 4.20iiD 12 N REPORTED FELT INFORMATION 018 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 188 6 AUG 1969 00:33:42.8 61 .400N 150.700W IV 1.\.BOMB 53 N REPORTED FELT INFORMATION 022 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = USE , flAGNITUDE(FRACTIONAL NOTATION ;'JWE)=IJ. 80. AUTHORITY- 189 18 AUG: 1969 1.3:57:10.0 62.254N 150.426~ 4.1 OMB 60 lll N 009 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION NOAA FEELS THIS IS A LESS RELIABLE SOLUTION ORIGINAL DATA SOURCE ; CGS 190 Hi OCT 1969 21:00:46.5 62.500N 151.300W 4.00NB 94 N REPORTED FELT INFORMATION 016 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = USE 191 lj DEC 1969 10:06:21.5 63.085N 151 . B33W 4.001'1B M N 013 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 192 30 J'M 1970 09; 1 5; 341. 9 61. 492N 146.62<3W 3.90i'ffi 33 N HYPOCENTER SOLUTION HELD AT 33 Kl'i (NORAl\L DEPTH) 014 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE ~ CGS LOCAL i'U\GNITUDE = 4. 1 0 SCALE "'I'lL ATYI'HORITY= CGS WOODWARD-CLYDE CONSULTANTS PAGE 14 CAT. DATE TIME( GMT) LJ\T LONG SL INTEN MAG Sl'l H DIS Q S L 0 C A T I 0 N A N D C 0 M M E N T S NO. DAY-110-YEAR HR-MIN-SEC ( MM) (1{11) (KM) -------------------------------------------------------------------------------------------~--------------------------------------~- 193 28 FEB 1970 06:56:49.9 63.073N 150.563W 4.10fill 120 N 017 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION -i p ORIGINAL DATA SOURCE = CGS (J:l .- rn 194 1 5 t1JIR 1970 12:58:24.9 62. 750N 150.839W o:J.OOMB 1 00 N 027 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION n ORIGINAL DATA SOURCE CGS I ........ 195 MAY 1970 20:58:12.5 63.600N 149.400W IV 4. 001'113 33 N REPORTED FELT INFORMATION 015 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION n 0 ORIGINAL DATA SOURCE = USE :z LOCAL MAGNITUDE = 4.20 SCALE =ML AUTHORITY= CGS -i :z 196 2 JUN 1970 02:59:31 . 3 61 .600N 151.700W IV 5.501'1B 95 N REPORTED FELT INFORMATION c: rn HYPOCENTER DEPTH SOLUTION RESTRAINED WITH P-P ARRIV11LS 0 091 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = USE MGNITUDE (FRACTIONAL NOTATION, AVE) =4. 7 5, AUTHORITY-BHK 197 1 0 JUN 1970 0<:1:15:16.8 61.311N 151 .086W 4.00MB 64 N 025 P AND/OR P' ARRIVALS-USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS 198 19 JUN 1970 01:42:11.1 63.534N 150.933W 4.20MB 33 N HYPOCENTER SOLUTION HELD AT 33 KM (NORMAL DEPTH) 013 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS LOCAL MAGNITUDE= 4.10 SCALE =t-11.. AUTHORITY= CGS 199 10 JUL 1970 09:16:44.2 61 .Gl67N 146.545W 4.201'113 35 N 036 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = CGS LOCAL MAGNITUDE= 4.70 SCALE =ML AUTHORITY= CGS 200 15 AUG 1970 16:55:51.5 63.581N 146.983W 4.30RB 33 l!C N HYPOCENTER SOLUTION HELD AT 33 Kf'l (NORI'IAL DEPTH) 008 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION NOAA FEELS THIS IS A LESS RELIABLE SOLUTION ORIGINAL DATA SOURCE = CGS 201 2 OCT 1970 05:55:40.9 62.351N 151.567W 4.1 OHB 84 l)l N 017 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION NOAA FEELS THIS IS A LESS RELIABLE SOLUTION ORIGINAL DATA SOURCE = NOS 202 31 OCT 1970 15:51 :38.4 62.1B7N 148.677W 4.20MB <14 N REPORTED FELT INFORMATION 014 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = NOS 203 3 NOV 1970 02:30:11.4 62.000N 151 .200W v 5.60MB 70 N REPORTED FELT INFORMATION 125 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = USE 204 10 DEC 1970 09:46:29.0 63.061N 151. 357W 4.30MB 118 N 021 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = NOS 205 20 DEC 1970 06:01:36.1 63.100N 151.400\;l 5.30flB 130 -----------------------------------------------------------------------------------------------------------------------------------·--; 085 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION > OJ ORIGINAL DATA SOURCE = USE r rn 206 5 JAN 1971 05:55:34.0 61 .421N 147.549W 4.501ffi 46 N REPORTED FELT INFORMATION n I 022 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION I-' ORIGINAL DATA SOURCE = NOS n 207 20 JAN 1971 02:07:34.3 63.293N 150.966W 4.601'1B 131 •N HYPOCENTER DEPTH SOLUTION RESTRAINED WITH P-P ARRIVALS 0 :z 032 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION --; ORIGINAL DATA SOURCE = NOS ....... :z c: 208 23 JAN 1971 15:12:14.7 63.091N 150. 750W 4.501'ffi 11 2 N 013 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION rn 0 ORIGINAL DATA SOURCE = NOS 209 19 FEB 1971 04:43:43.8 63.206N 150.474W 4.00MB 115 N 016 P AND/OR P' ARRIVALS USED IN HYPOCEN'l'ER SOLUTION ORIGINAL DATA SOURCE = NOS 210 21 FEB 1971 16:08:09.1 62.574N 151 .348W 4.201'1B 91 N 027 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = NOS 211 21 FEB 1971 18:10: 3<!.6 63.075N 150.3<16W 4.70MB 115 N 014 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = NOS 212 2 i'IAR 1971 12:46:36.4 63.394N 149.822W 4.80MB 111 N 020 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = NOS 213 9 MAR 1971 08:08:53.9 63.968N 149.829W 4.30PlB 140 N 016 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = NOS 214 9 I'IAR 1971 10:56:36.0 63.960N 149.823W 4.001'lB 138 N 013 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = NOS 215 5 Ml\Y 1971 10:32:44.4 61.733N 151 .456W 4.1 OMB 75 N 014 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = NOS 216 14 MAY 1971 15:00:35.1 62.457N 151.137W 4.30MB 82 N 020 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = NOS 217 16 MAY 1971 16:50:57.4 63.103N 148. 316W 4.1 Olm 77 N 008 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = NOS 218 2 JUN 1971 19:06:32.9 61.030N 151. 256W III 5.00MB 29 N REPORTED FELT INFORMATION 048 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = NOS LOCAL MAGNITUDE= 5.50 SCALE =ML AUTHORITY= NOS 219 26 JUL 1971 16:17:35.6 63.283N 149.726W 4. 1 01'113 33 lit N REPORTED FELT INFORMATION HYPOCENTER SOLUTION HELD AT 33 KM (NORMAL DEPTH) 009 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION NOAA FEELS THIS IS A LESS RELIABLE SOLUTION ORIGINAL DATA SOURCE = ERL LOCAL MAGNITUDE = 4.40 SCALE =ML AUTHORITY= ERL WOODWARD-CLYDE CONSULTANTS PAGE 16 CAT. Dl\TE TIME(GMT) IJIT LONG SL INTEN MAG SM H DIS 0 S L 0 C A T I 0 N A N D C 0 1'1 1'1 E N T S NO. Dl\Y-110-YEAR HR-I'IIN-SEC (KM) ( KM)(KM) ---------------------------------------------------------------------------------------------------------------------~------------·~- 220 30 JUL 1971 02:07:52.1 62.079N 151 .374W 4.201ffi 81 Jil N 020 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION -I p NOAA FEELS THIS IS A LESS RELIABLE SOLUTION CIJ r ORIGINAL DATA SOURCE = ERL rn ('"") 221 12 SEP 1971 23:46:10.1 63.593N 150.904W 3.BOMB 8 N 011 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION I ORIGINAL DATA SOURCE ; ERL ,....... LOCAL Ml\G~ITUDE = 4.10 SCALE ;I'lL AUTHORITY= ERL ('"") 0 222 22 ocr 1971 23:10:59.0 63. 140N 151 .1 09W 4.601ffi 133 N 027 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION z ORIGINAL DATA SOURCE = ERL -I ....... z 223 30 DEC 1971 17:56:03.5 61 .145N 150.360W III 4. 1 Olffi 41 N REPORTED FELT INFORMATION c rn 014 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION 0 ORIGINAL DATA SOURCE = ERL LOCAL MAGNITUDE= 3.70 SCALE =I'lL AUTHORITY= ERL 224 1 5 Jl\N 1972 09:35:44.8 63.17BN 149.997W 4.00MB 91 lll N 009 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION NOAA FEELS THIS IS A LESS RELIABLE SOLUTION ORIGINAL DATA SOURCE = ERL 225 1 1 APR 1972 18:21:35.5 62.023N 150.41 BW 4.50MB "18 N 025 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = ERL LOCAL MAGNITUDE = 4.20 SCALE =I'lL AUTHORITY= ERL 226 16 APR 1972 18:35:39.3 63.527N 147.713W 4.1 OMB 11 N REPORTED FELT INFORMATION 026 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = ERL LOCAL MAGNITUDE = 4.60 SCALE =I'lL AUTHORITY= ERL 227 25 APR 1972 13:35:54. 1 61 .9B4N 148.823W 4.60MB 58 N 044 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = ERL 228 28 APR 1972 19:05:15.3 63.613N 149.909W 4.70f'IB 131 N 025 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = ERL 229 22 JUN 1972 05:57:34.2 61. 417N 147.491W II 4.501'1B 48 N REPORTED FELT INFORMATION 029 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = ERL 230 1 ocr 1972 10:08:49.7 62. 743N 149.082W II 4.701'1B 76 N REPORTED FELT INFORMATION 036 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = ERL 231 21 OCT 1972 19:52:05.4 63.154N 151 .063W IV 5.40MB 132 N REPORTED FELT INFORMATION HYPOCENTER DEPTH SOLUTION RESTRAINED WITH P-P ARRIVALS 076 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = ERL 232 16 FEB 1973 02:25:23.8 62.9971'1 150.624W 4. 30tiD I 09 N 233 5 MAR 1973 08:30:49.2 63.734N 148.442W 4.001"1B 106 N 025 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = ERL 234 16 MAR 1973 02:49:19.4 62.218N 151 .056W 4.30MB 72 N 035 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION (""") I ORIGINAL DATA SOURCE = ERL ...... 235 24 1'11\R 1973 07:51:43.5 63.218N 150.833W 4.201ffi 122 N 014 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION (""") ORIGINAL DATA SOURCE = ERL 0 z -i 236 4 APR 1973 15:43:26.6 62.974N 150.835W 4.20MB 124 N 021 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ...... z ORIGINAL DATA SOURCE = ERL c:: [Tl 0 237 22 APR 1973 03:40:5<:\. 1 63.597N 150.946W 4.40tffi 14 N 030 P AND/OR P' ARRIVI'ILS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = ERL LOCAL MAGNITUDE = 4.50 SCALE =ML AUTHORITY'= ERL 230 18 1'11\Y 1973 18:32:55.7 63.070N 150.951W 4.70ND 1 28 N 035 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DfiTA SOURCE = ERL 239 25 Ml\Y 1973 03:10:15.0 63.205N 150.741W 4.00MB 1 28 N 023 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINfiL DATA SOURCE = ERL 240 22 JUL 1973 07:33:43.8 63.803N 149.110W 4.10lm 120 N 014 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = ERL 241 19 AUG 1973 17:34:51.3 63.235N 150. 426W 4.1 OMB 130 N 017 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = ERL 242 31 AUG 1973 02:30:57.9· 61 .096N 147 .414W III 5.1 OMB 49 N REPORTED FELT INFORMATION 100 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = GS MAGNITUDE= 5.0 USING NOAA AVERAGE MS (IASPEI FORMUI.A) 243 6 SEP 1973 10:59:36.7 61 .039N 146.828W III 5.50i'IB 29 N REPORTED FELT INFORMATION HYPOCENTER DEPTH SOLUTION RESTRAINED WITH P-P ARRIVALS 087 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = GS MAGNITUDE = 5. 3 USING NOAA AVERAGE MS (IASPEI FORMULA) LOCAL MAGNITUDE = 5.50 SCALE =ML AUTHORITY= PMR 244 24 JAN 1974 18:43:26.8 61 .588N 147.626W v 13.8011B 40 N REPORTED FELT INFORMATION 65 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = GS LOCAL MAGNITUDE 5.20 SCALE =I'lL AUTHORITY= PMR 245 2 FEB 1974 15:55:28.3 61 .602N 147.603W 5.1 OMB iJB N REPORTED FELT INFORMATION 81 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = GS MAGNITUDE= 4.7 USING NOAA AVERAGE MS (IASPEI FORMULA) WOODWARD-CLYDE CONSULTANTS PAGE 18 Cl\T. Dl\TE TIME(GMT) LAT LONG SL INTEN MAG Sl'l H DIS Q S L 0 C A T I 0 N A N D C 0 M 1'1 E N T S NO. Dl\Y-110-YEAR HR-MIN-SEC ( MM) ( KM )( KM) -------------------------------------------~-·~-------------------------------------------------------------------------------------- 246 5 FEB 1974 02:25:22.0 62.703N 148.854W v 5.00MB 75 N REPORTED FELT INFORMATION -i )::> 61 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION co r ORIGINAL DATA SOURCE = GS fT1 247 15 FEB 1974 06:06:28.5 63.144N 150.763\i 4.50MB 126 N 32 P AND/OR P' ARRIVALS USED IN n HYPOCENTER SOLUTION I ORIGINAL DATA SOURCE = GS ....... 248 10 MR 1974 1 0: 00: '14. 1 63.160N 150.503W 4.50MB 117 N REPORTED FELT INFORMATION n 0 36 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION :z ORIGINAL DATA SOURCE = GS -l ,__.. :z 249 8 MAY 1974 04:27:13.1 63.669N 150.727W 4.60MB 11 N REPORTED FELT INFORMATION c fT1 62 P liND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION 0 ORIGINAL DATA SOURCE = GS LOCAL i'IAGNITUDE = 4. 70 SCALE =I'lL AUTHORITY= PMR 250 21 i'IAY 1974 23:31:41.2 63.312N 151.245W II 4.20NB 1 2 N REPORTED FELT INFORMATION 29 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = GS LOCAL MAGNITUDE = 4.60 SCALE =I'lL AUTHORITY= P11R 251 2.:1 JUN 1974 21:20:22.1 63.167N 149.881W 5.50i'lB 75 N 18 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = GS 252 11 JUL 1974 02:17:57.8 62.388N 151.253W 4.20MB 92 N 25 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTIOt~ ORIGINAL DATA SOURCE = GS 253 13 JUL 1974 14:4B:50.0 62.227N 151 .217W IV 4.40MB 85 N REPORTED FELT INFORMATION 30 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = GS 254 DEC 1974 15:56:32.3 62.210N 150. 532W 4.00MB 64 N 20 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = GS 255 10 DEC 1974 16:05:18.2 61 .BOBN 146.B93W .;1.40MB 27 N 11 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTIOtl ORIGINAL DATA SOURCE = GS LOCAL MGNITUDE = 3 . 30 SCALE =ML AUTHORITY= PRR 256 29 DEC 1974 18:25:00.7 61 .597N 150. 511W v 5.601'1B 67 N REPORTED FELT INFORMATION HYPOCENTER DEPTil SOLUTION RESTRAINED WITH P-P ARRIVALS 81 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = GS 257 30 DEC 1974 03:33:16.6 61 .9B2N 149.686W v 5.1 OMB 62 N REPORTED FELT INFORMATION HYPOC~NTER DEPTH SOLUTION RESTRAINED WITH P-P ARRIVALS 88 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = GS 258 1 JAN 1975 03:55:12.0 61.909N 1~9.738W v 5.90MB 66 N REPORTED DAMAGE 118 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = GS 259 13 JAN 1975 00:31:55.6 61.434N 150.494W IV 4.BOMB 66 N REPORTED FELT INFORMATION 45 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = GS n 260 20 JAN 1975 05:51:23.1 63.770N 149.233W 4.40MB 123 N 19 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION I ....... ORIGINAL DATA SOURCE = cs n 261 12 FEB 1975 15:45:35.1 63.518N 148.725\il IV 4.00HB 33 N REPORTED FELT INFORMATION 0 z HYPOCENTER SOLUTION HELD AT 33 KM (NORMAL DEPTH) ...; :!3 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ...... z ORIGINAL DATA SOURCE = GS c LOCAL .MAGNITUDE = 4. 50 6CALE =I'lL AUTHORITY= Pl'lR rrl CJ 262 12 i'll\R 1975 14:05:31.5 61 .915N 150.307W 3.90MB 10 N REPORTED FELT INFORMATION 22 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = GS LOCAL I'IAGNITUDE = 4. 00 SCALE =ML AUTHORITY= PMR 263 1 3 APR 1975 19:32:48.8 63.401N 149.791W 4.0011B 114 N 21 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DhTA SOURCE = GS 264 18 MAY 1975 15:42:59.1 63.170N 150. 263W v 5.40HB 106 N REPORTED FELT INFORMATION HYPOCENTER DEPTH SOLUTION RESTRAINED WITH P-P ARRIVALS 223 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL OAT~ SOURCE = GS 265 20 MAY 1975 16:29:50.0 63.028N 150.003W 4.20MB 125 N 14 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = GS 266 11 JUN 1975 05:14:08.2 62 .165N 149.635W 4.30MB 59 N REPORTED FELT INFORMATION 41 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = GS 267 24 JUN 1975 12:15:31.3 63.098N 150.946W 4.00MB 1 33 N 18 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = cs 268 AUG 1975 07:04:33.0 61. 919N 150. 763W 4.60MB 79 N 22 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = GS 269 17 SEP 1975 13:18:14.2 63.422N 149.827W 4.60MII 133 N 20 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = GS 270 21 OCT 1975 01:16:28.7 61. 313N 147.371W 4.6011B 33 N HYPOCENTER SOLUTION HELD AT 33 KM (NORMAL DEPTH) 17 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DhTA SOURCE = GS 271 24 DEC 1975 14:25:21.6 62.571N 1 48. 193W 4. 1OMB 72 N 28 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = GS 272 1 3 1'11\R 1976 14:33:42.5 63.503N l48.673W v 3.90MB 22 N REPORTED FELT INFORMATION 17 P AND/OR P' ARRIVALS USED IN HYPOCEtlTER SOLUTION WOODWARD-CLYDE CONSULTANTS I? AGE 20 Cl\T. DATE TIME ( Gf<IT) Ll\T LONG SL INTEN Ml\G SM H DIS 0 S L 0 C A T I 0 N A N D C 0 1'1 1'1 E N T S NO. DAY-1'10-YEAR HR-MIN-SEC (I'IM) ( I<M) ( KM) --------------------------------------------------------------------------------------~---------------------------------------------ORIGINAL DATA SOURCE = GS -t LOCAL MAGNITUDE = 4.20 sctu.E =ML AUTHORITY= PI'IR :t=- 0:0 273 26 1'11\R 1976 14:40:14.2 63.602N 147.653W IV 4.101'1B 33 N REPORTED FELT INFORMATION r rn HYPOCENTER SOLUTION HELD AT 33 KM (NORMAL DEPTH) {"""") 26 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLI.rriON I ORIGINAL DATA SOURCE = GS ....... LOCAL tmGNITUDE = IJ. 20 SCALE =MI. AUTHORITY= PI'IR {"""") 0 274 B l'U\Y 1976 11:25:36.3 61.620N 151 .517W IV <!.<lOMB 16 ~ REPORTED FELT INFORMATION z 43 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION -t ...... ORIGINAL DATA SOURCE = GS z LOCAL ru\GNITUDE = 4 • IJO SCALE =MI. AUTHORITY= PI'IR c rr1 0 275 11 MAY 1976 16:46:15.8 61.491N 146.966W III 4.20MB 67 N REPORTED FELT INFORMATION 1B P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL Dl\TA SOURCE = G6 276 24 JUI)l 1976 13:36:59.2 61.965N 150.S95W 4.BOMB 73 N 19 P AND/OR P' ARRIVALS .USED IN HYPOCENTER SOLI.rriON ORIGINAL DATA SOURCE = GS 277 11 JUL 1976 02:00:11.1 63.301N 150.B03W 4.50MB 133 N 26 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = GS 278 12 JUL 1976 01:59: 15.3 62. 858N 150.6B2W 4.601'1B 128 N 11 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = GS 279 15 JUL 1976 08:09:(17.4 62.700N HI9.831W IV 4.201'1B 24 N REPORTED FELT INFORMATION 32 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = GS LOC1l.L MAGNITUDE = 4. 60 SCALE =ML AUTHORITY= PI'IR 280 30 JUL 1976 13:54:32.2 61.332N 147.445W 3.90i1B 40 N REPORTED FELT INFORMATION 22 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = GS LOCAL MAGNITUDE = 4.00 SCALE =MI.. AUTHORITY= PMR 281 27 AUG 1976 17:07:23.6 62.2~3N 149.471W 4.001'1B 65 N 14 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = GS LOCAL MAGNITUDE "' 3. 70 SCALE =AI. AUTHORITY= Pl'lR 282 . 30 MJG 1976 10:01:12.9 61.301N 151.431W 4.1 OMB 32 N 16 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = GS 283 4 SEP 1976 23:23:46.0 62.931N 150.653W 5.40MB 123 N 14 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = GS 28<1 26 6EP 1976 08:25:41.8 61.732N 151 .697W ~.omm 110 N 12 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = GS 285 25 SEP 1976 09:23:5-3.0 61 .472N 151 .921W 4l.OOMB 95 lll N 11 1? ll.ND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION NOl'!.n FEELS THIS IS A LESS RELIABLE SOL 286 18 OCT 1916 00:36:31.6 63.290N 150.731W IV 4.90MB 126 N REPORTED FELT INFORMATION · 63 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DnTA SOURCE = GS n I ~~ 281 24 OCT 1976 11:19:53.1 62.647N 149.139W 4.90lill 15 N REPORTED FELT INFORMATION 96 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION n ORIGINAL DATA SOURCE = GS 0 :z -1 288 :n OCT 1976 03:43:41.4 61 .708N 151. 543W 4.20HB 98 N 1 5 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ...... :z ORIGINAL DATA SOURCE GS c: JTI 289 3 NOV 1916 16:40:44.6 63. OB5N 150. 951W 4.401m 0 1 33 N 16 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = GS 290 4 NOV 1916 01:04:38.9 63.643N 150.839W 4.301m 12 N 14 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = GS LOCAL ftAGNITUDE = 4.30 SCALE =ML AUTHORITY= PMR 291 4 DEC 1916 04:20:22.8 63.214N 150.196W 4.301'1B 129 N 14 P l\ND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = GS 292 13 DEC 1916 11:21:53.6 61 .B13N 150.103W 4.30MB 14 N 15 P AND/OR P' ARRIVALS USED IN HYF()CENTER SOLUTION ORIGINAL DATA SOURCE = GS 293 24 DEC 1916 01:50:11.2 63.411N 151.409W <1. 1 ON' 33 N HYPOCENTER SOLUTION HELD AT 33 KM (NORMAL DEPTH) 13 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = GS LOCAL MAGNITUDE= 4.10 SCALE =I'lL AUTHORITY= PMR 294 15 JAN 1911 21:00:43.2 62.B01N 150. 3141-l 4.30MB 100 N 16 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = GS 295 FEB 1911 08:51:45.1 62 .152N 151 .285W <J.omm 83 N 11 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = GS 296 5 MAR 1911 06:13:01.1 6J.220N 150.509W .:1.20MB 122 N 20 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = GS 291 20 APR 1917 15:02:51 .6 62.B48N 151.046W 4.501m 1 HI N 20 P 1'\ND/OR P' i\RRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = GS "299 25 lWR 1917 02:28:5{1.4 61.~2(!N Hl1.19BW a.20N' 36 N 13 P l\ND/OR P' ARRIVALS U~ IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE c GS ., LOCAL MAGNITUDE = 4. 20 SCl\LE '"'MI. IUJTHORITY:z PMR 299 MY 1917 01:56:00.7 63.205N 150.B69W .a.oo;m 131i N 1 2 P MID/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGIN~L DATA SOURCE ~ GS 300 2 JUN 1911 16:29;4!6.3 61.314N 150.329W v 3.601'!B 57 N REPORTED FELT INFORMTION 19 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION WOODWARD-CLYDE CONSULTANTS PT>.GE 22 CAT. DATE TIME( GMT) IJ\T LONG SL INTEN 111\G SM H DIS Q S L 0 C A T I 0 N A N 0 C 0 M 1'1 E N T S NO. DAY-110-YEAR HR-MIN-SEC (MM) ( Kl'l) ( Kl'l) -----------------------------------------------------------------------~------------------------------------------------------------ORIGINAL DATA SOURCE = GS -l p 301 6 JUN 1977 1 0 : 0(1: 11 . 5 62.163N 149.54BW III <J.10MD 60 N REPORTED FELT INFORMATION co I 17 P AND/OR P' ARRIVALS USED IN HYPOCEN'fER SOLUTION rr1 ORIGINAL DATA SOURCE = GS n I 302 17 JUN 1977 08:26:28.9 61.492N 150.319W IV 4.30MB 74 N REPORTED FELT INFORMATION ~ 30 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = GS n 0 z 303 8 JUL 1977 19:59:39.9 61.1681.'1 150.B55W IV 4.701"l13 72 N REPORTED FELT INFORMATION -l ,_. 73 P AND/OR P' ARRIV1:1LS USED IN HYPOCENTER SOLUTION z ORIGINAL DATA SOURCE = GS c:: rr1 CJ 304 22 JUL 1977 05:57:00.5 61.027N 150,401W 3.8011B 51 N REPORTED FELT INFORMATION 22 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = GS LOCAL MAGNITUDE = 4.00 SCALE =ML AUTHORITY= PMR 305 23 AUG 1977 13:4'12:4!0.1 63. 719N 149.3791>! 4.1 OMB 126 N 20 I? JUm/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = GS 306 30 AUG 1977 06:50:39.9 63.161N 151.109111 IV 5.00MB 130 N REPORTED FELT INFORMATION HYPOCENTER DEPTH SOLUTION RESTRAINED WITH P-P ARRIVALS 1 21 P AND/ORP' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = GS 307 9 SEP 1977 1 5: 58 : 56 • <I 62.1871.'1 149.527W 4.60HB 59 N REPORTED FELT INFOIDiATION 33 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = GS 306 19 OCT 1977 02:Hi:02.6 62.B83N 150. 559W 5.00i'ID 102 N 1 07 P M-ID/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL OAT~ SOURCE = GS 309 6 NOV 1977 09:23:28.2 61.994N 150. 734W iJ .1 OHB 78 N 15 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = GS 310 20 NOV 1977 18:53:57.8 62.429N 150.661W v 4.901'lB 79 N REPORTED FELT INFORMATION 61 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE GS LOCAL MAGNITUDE = 4.90 SCALE =I'lL AUTHORITY= PMR 311 5 JAN 1978 19:56:09.8 61 .329N 151.650W III 4.40Kf:l 110 N POSSIBLE TSUNAMI GENE~~TED BY EARTHQUAKE POSSIBLE SEICHE ASSOCIATED WITH EARTHQUAKE REPORTED FELT INFORMATION t8 P AND/OR P' ARRIVI!LS USED IN HYPOCENTER SOLUTION ORIGINI!L DATA SOURCE = GS 312 28 JAN 1978 02:25:01 .6 63.063N 150.963W <L40iiB 126 N POSSIBLE TSUNAMI GENERATED BY EARTHQUAKE POSSIBLE SEICHE ASSOCIATED WITH &)RTHQUAKE 35 P AND/OR ARRIVALS IN ---i 313 31 Mll.R 1978 00:38:13.4 61.766N 151 .409W IV 5.1 OMB 90 N POSSIBLE TSUNAMI GENERATED BY EARTHQUAKE ):;> OJ POSSIBLE SEICHE ASSOCIATED WITH EARTHQUAKE I REPORTED FELT INFORMATION rn HYPOCENTER DEPTH SOLUTION RESTRAINED WITH P-P ARRIVALS n I 154 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ...... ORIGINAL DATA SOURCE = GS n 314 10 APR 1978 10:47:02.9 63.075N 150.640W 4.201'1B 131 N POSSIBLE TSUNnKI GENERATED BY EARTHQUAKE 0 :z POSSIBLE SEIC~E ASSOCIATED WITH EARTHQUAKE -i JJ P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ...... z ORIGINAL DATA SOURCE = GS c: rn 315 5 Mll.Y 1978 05:32:47.4 63.302N 150.971W IV 5.20!'tB 134 N POSSIBLE TSUNAMI GENERATED BY EARTHQUAKE 0 POSSIBLE SEICHE ASSOCIATED WITH EARTHQUAKE REPORTED FELT INFORMATION 1 38 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = GS 316 12 MAY 1978 12:16:03.9 62.250N 149.398W IV 5.1 OMEI 67 N POSSIBLE TSUNAMI GENERATED BY EARTHQUAKE POSSIBLE SEICHE ASSOCIATED WITH EARTHQUAKE REPORTED FELT INFORMATION 100 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = GS 317 23 JUL 1978 15:19:35.5 63.307N 147.256W 5. OOI'IB 33 N POSSIBLE TSUNAMI GENERATED BY EARTHQUAKE POSSIBLE SEICHE ASSOCIATED WITH EARTHQUARE REPORTED FELT INFORMATION HYPOCENTER SOLUTION HELD AT 33 KM (NORMAL DEPTH) 50 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = GS LOCAL MAGNITUDE = 4.80 SCALE =J'IL AUTHORITY= PMR 318 8 AUG 1978 09:30:03.3 61.3BBN 146.908W IV 4.30MB 53 N POSSIBLE TSUNAMI GENERATED BY EhRTHQUAKE POSSIBLE SEICHE ASSOCIATED WITH EARTHQUAKE REPORTED FELT INFORMATION 54 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = GS 319 13 AUG 1978 00:49:41.0 62.2BON 149.709W 4.10MB 65 N POSSIBLE TSUNAMI GENERATED BY EARTHQUAKE POSSIBLE SEICHE ASSOCIATED WITH EARTHQUAKE REPORTED FELT INFORMATION 36 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = GS 320 22 AUG 1978 03:20:07.2 61.649N 151.961W 4.00i'ffi 123 l;l N POSSIBLE TSUNAMI GENERATED BY EARTHQUAKE POSSIBLE SEICHE ASSOCIATED WITH EARTHQUAKE IB P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION NOAA FEELS THIS IS A LESS RELIABLE SOLUTION ORIGINAL DATA SOURCE = GS WOODWARD-CLYDE CONSULTANTS PI\GE 24 Cl\T. DhTE TIME( GMT) UIT LONG SL INTEN l"lAG Sl'l H DIS Q S LOCATION AND C 0 M M E J:l T S NO. DAY-1'10-YEl\R HR-MIN-SEC (MM) ( Kl'l) ( KH) ----------------------------------------------------------------------------------------------------------~------------------------- 321 21 SEP 1978 14:45:19.6 61 .108N 151 .808W IV 4.501'iEl 81 * w POSSIBLE TSUNAMI GENEAA'l'ED BY EI\RTHQIJAKE ---1 POSSIBLE SEICHE ASSOCIATED WITH EARTHQUAKE ;.::, ro REPORTED FELT INFORMATION r 3-9 P AND/OR P' ARRIVALS USED IN HY~OCENTER SOLUTION rn NOAA FEELS THIS IS A LESS RELIABLE SOLUTION n I ORIGINAL DATA SOURCE = GS ~ 322 28 SEP 1970 23:53:13.7 63.986N 147.712W 4.40i'JB 33 N POSSIBLE TSUNAMI ~~ERATED BY EARTHQUAKE n POSSIBLE SEIC~E ASSOCIATED WITH EARTHQUAKE 0 z REPORTED FELT INFORHl\TION ---1 HYPOCENTER SOLUTION HELD AT 33 KM (NORMAL DEPTH) ,_. z 26 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION c: ORIGINAL DATA SOURCE = GS rn 0 LOCAL MAGNITUDE = 4.50 SCALE =ML AUTHORITY= Pl'ffi 323 15 OCT 197B 05:5.;\:05.2 61 .932N 150.665W III 4.60N' 6 M POSSIBLE TSUNAMI GENERnTED BY EARTHQUAKE POSSIBLE SEICHE ASSOCI~TED WITH EARTHQUAKE REPORTED FELT INFORMATION 17 P AND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = GS LOCAL MAGNITUDE = <\1 • 60 SCl'lLE =I'lL l)UTHORIT'l= li?i'IR 32•1 19 NOV 1976 12: 06: 1 3. '1 63.32SN 161.119W IJ.OOMB 33 >11 N POSSIBLE TSUNAMI GENERATED BY EARTHQUAKE POSSIBLE SEICRE ASSOCIATED WITH EARTHQUAKE HYPOCENTER SOLUTION HELD AT 33 KM (NORMAL DEPTH) 39 P AND/OR P' ARRIV~LS USED IN HYPOCENTER SOLUTION NOAA FEELS THIS IS 1\ LESS RELilillLE SOLUTIOr:-1 ORIGINAL DATA SOURCE = GS LOCAL MAGNITUDE = 4.30 SCALE =tu. AUTHORITY= Plm 325 2<Cl NOV 1978 00:28:12.8 62.027W 150.519W 43.5000 741 N POSSIBLE TSUNAMI GENERATED BY EARTHQUAKE POSSIBLE SEICHE ASSOCIATED WITH EARTHQUAKE REPORTED FELT INFORMATION .37 P fiND/OR P' ARRIV!l.LS USED IN HYPOCENTER SOLUTION ORIGINAL OAT~ SOURCE = GS 326 3 DEC 1978 19:39:31.2 62.306N 149.750W IV <L 70i"'rl 7C N POSSIBLE TSUNMI GENERATED BY ElU<THQUM<E POSSIBLE SEICHE ASSOCIATED WITH EARTHQUAKE REPORTED FELT INFORMATION 78 P P.ND/OR P' ARRIVALS USED IN HYPOCENTER SOLUTION ORIGINAL DATA SOURCE = GS 327 17 DEC 1978 1 3: 15:26.0 63.953N 147.424W IV 4.SO!m 22 N POSSIBLE TSUNAMI GENERATED BY EARTHQUAKE POSSIBLE SEICHE ASSOCIATED WITH EARTHQUAKE REPORTED FELT INFORMATION 813 P AND/OR P' ARRIV~LS USED IN HYPOCENTER SOLUTION ORIGIN~L DAT~ SOURCE = GS LOC~L AAGtUTUDE = 41. 60 SCALE :I'lL AUTHORITY"' Pi'IR APPENDIX D -SUSTINA STUDY AREA MICROEARTHQUAKE CATALOG The catalog of microearthquakes that were recorded during the summer field study of 1980 is presented in Table D-1. The data collection methodology is discussed in Appendix B; analyses and interpretations are discussed in Section 9. The explanation for the catalog headings are as follows: CAT. NO. DATE TIME LAT, LONG MAG H -Sequence number of the' listed events. -Date the earthquake occurred by day, month, and year according to the origin time in Universal Coordinated Time (UCT). -Origin time of the earthquake in hours, minutes, and seconds in Universal Coordinated Time (UCT). Time is rounded to the nearest 0.1 seconds. -North latitude and west longitude of the epicenter in degrees. Implied accuracy is to the nearest 0.001 degrees (0.1 km), but uncertainty in the location is more properly interpreted from the RMS and ERH values. Magnitude of the earthquake calculated using the dura- tion of coda waves. Values are calibrated to be equi valent to local Richer magnitudes (ML)· -Depth of earthquake (focal depth) in kilometers. Val- ues are rounded to the nearest one kilometer. D - 1 S Source of location and magnitude values; all were cal- culated by Woodward-Clyde Consultants. LOCATION AND -Six parameters are used to measure the quality COMMENTS earthquake location. NO The total number of P and S arrivals used in the location. GAP Dl RMS ERH ERZ Largest azimuthal separation of the stat ions, in degrees, from the epicenter. Distance in kilometers from epicenter to closest station used to locate the event. -Root-mean-square travel-time residual, in seconds, for all the stations used in the location. The residual is defined as (t0 -tc), where t 0 is the observed travel time and tc is the calculated tra- vel time from the earthquake focus to each station. Greatest horizontal standard error of the epicen- ter, in kilometers. Standard error of the focal depth, in kilometers. D - 2 2 3 5 6 7 8 9 10 11 1 2 1 3 14 15 16 17 18 19 20 21 22 25 26 2 JUL 1980 09:19:02,4 62.496N 14B.826W 2 JUL 1980 10:42:56.5 62.874N 148.676~ 2 JUL 1980 10;49:03.3 62.846N 148,848W 2 JUL 1980 22:20:11.7 62.894N 140.625W 3 JUL 1980 12:06:44.4 63.087N 147.871W 4 JUL 1980 17:33:48.8 62.557N 150.050W 5 JUL 1980 03:56:14.3 62.300N 148.383W 5 JUL 1900 06:5~:09.9 62.967N 148.749W 5 JUL 1980 23:27:54.1 62.626N 148.B61W 6 JUL 1980 01:54:19.3 62.613N 14B.917W 6 JUL 1900 15:29:11.0 62.491N 148.270W 7 JUL 1980 16:35:37.8 62.593N 148.886W 7 JUL 1980 18:33:35.6 52.654N 149.549W 8 JUL 1900 01:22:07.8 63.066N 149.169W 9 JUL 1980 07:03:53.4 62.701N 148.502W 9 JUL 1980 03:27:47.4 62.939N 149.514W 9 JUL 1980 21:27:02.2 62.375N 148.660W 10 JUL 1980 03:39:49.9 62.981N 149.326W 10 JUL 1980 04:46:00.9 62.392N 140.643W 10 JOL 1980 10:54:28.0 63.175N 149.034W 11 JUL 1900 10:09:35.6 62.419N 147.992W 12 JUL 1980 09:13:08.2 62.617N 149.150W 12 JUL 1900 14:22:56.5 62.480N 149.415W 13 JUL 1980 05:57:43.0 62.596N 148.965W 13 JUL 1980 10:17:45.0 63.173N 1~8.757W 13 JUL 1980 11:15:44.2 62.426N 148.998W 2.56 2.81 1 • 93 1 • 70 1 • 54 I .87 2. 11 2.81 1. 34 0.93 2.55 1 .46 2.16 1 • 40 2.05 3.24 2.77 2.31J 2.21 3. 11 3.03 I. 75 1 .96 3.68 2.53 2.61 52 15 16 15 Hl 19 68 16 17 15 66 15 68 131 45 87 47 73 61 62 55 9 WC NO= 10,GnP-275,01= 13,RMS= .06,ERH= 1.1 ,ERZ= 1.1 we H<F: 1 o ,GAP= 21 o ,o1 S,RMS= ,30,ERH= 3.3,ERZ= 3.4 HC NO=-10,Gl\P-232,01= 15,RM.S= .35,ERH= 5.4,ERZ= 5.8 we NO= a.~~= 262,01= 9,RMs= .14,ERH= 2.6,ERZ= 2.2 WC NO= 7,GAP= 287,01 18,RMS= .06,ERH= 1.5,ERZ= 2.1 WC NO= 9,GAP= 326,01= 27,RMS= .12,ERH= 2.9,ERZ= 1.1 WC NO= B,GAP= 299,01= 32,RMS= .21 ,ERH= 3.8,ERZ= 1.9 we NO= 10,GJU>= 193,01= 29,Ri'IS= .09,ERH= 1.6,ERZ= 1.9 WC NO= 12,GAP= 161 ,01= 1 ,RMs: .32,ERH= 2.B,ERZ= 3.6 WC NO= 12,~ 105,01= 4,RNS= .32,ERH= 2.7,ERZ= 3.5 we NO= 16,GAP= 227,01= 11,RMS= .3B,ERH= 4.4,ERZ= 5.2 OC NO= 14,Gl\.P= 164,01= 3,RNS= .38,ERH:: 2.9,ERZ= 6.4 WC NO= 14,GAP= 164,01= 5,RMS= .17,ERH= 2.3,ERZ= 2.3 we NO= 14,~ 212,01= 19,RMS= .26,ERH= 2.3,ERZ= 3.7 WC NO= 13,GAP= 122,01= 26,RMS= .14,ERH= 1 .5,ERZ= 2.3 WC NO= 9,GAP= 12~,01= J,RMS= .17,ERH= 3.0,ERZ= 3.8 WC NO= 12,GAP= 240,01= 35,RMS= .21 ,ERH= 3.3,ERZ= 4.9 WC NO= 13,GJ\P, 115,01= 12,Rl'll? .29,ERH= 3.6,ERZ= 5.1 WC NO= 15,GAP= 236,01= 33,RMS= .43,ERH= 5.2,ERZ= 6.9 WC NO= 13,Gl\.P= 137,01= 36,RMS= ,20,ERH= 2.1 ,ERZ= 3.3 we NO= 15,GAP= 278,01= 16,RMS= .39,ERH= 5.5,ERZ= 7.8 we NO= 15,GAP= 147,01= 15,RMS= .23,ERH= 2.5,ERZ= 3.1 WC NO= 11 ,GAP= 274,01= B,RMS= ,,1 ,ERH= 2.0,ERZ= 2.1 we NO= 12,GJ.\P= 162,01= 6,RMS= .13,ERH= LG,ERZ= 2.1 WC NO= 14,~ 236,01= 25,RMS= .25,ERH= 2.4,ERZ= 8.8 WC NO= 16,Gl\.P= 227,01= 22,MS= .14,ERH= 1.8,ERZ= 2.0 W00~1ARD-CLYDE CONSULTANTS OJ r-rn 0 I 1-'" PAGE 2 CAT. DATE TIHE(Gm') LAT LONG NO. DAY-M.O-YEAR HR-IUN-SEC 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 45 46 47 48 49 50 51 13 JUL 1980 19:00:45.3 62.820N 148.343W 13 JUL 1900 20:48:41.8 62.924N 149.78BW 15 JUL 1980 13:57:19.3 62.617N 148.867W 15 JUL 1980 16:03:24.1 62.453N 148.629W 15 JUL 1980 20:12:09.2 62.583N 148.138W 15 JUL 1980 20:45:39.5 62.471N 148.290W 16 JUL 1980 01:10:04.8 62.530N 148.626W 16 JUL 1980 15:12:26.9 62.743N 148.914W 17 JUL 1980 08:53:09.0 62.596N 148.901W 17 JUL 1980 10:06:26.5 62.554N 148.346W 17 JUL 1980 12:54:14.7 62.629N 148.794W 17 JUL 1980 12:57:29.9 62.601N 140.874W 17 JUL 1980 15:53:21.1 62.600N 148.876W 17 JUL 1980 21:34:03.6 62.627N 148.861W 18 JUL 1980 04:38:45.6 62.596N 14B.BBBW 18 JUL 1980 23:40:14.2 62.871N 149.379W 19 JUL 1980 08:07:10.4 62.427N 148.458W 19 JUL 1900 10:33:13.1 62.616N lo08.833W 19 JUL 1980 14:21:23.5 63.002N 148.450W 19 JUL 1980 20:19:48.2 62.671N 149.611W 19 JUL 1980 20:40:02.8 62.475N 148.055W 19 JUL 1980 20:52:55.5 62.793N 149.474W 20 JUL 1980 06:12:03.8 62.890N 149.060W 20 JUL 1980 08:01:25.9 62.417N 148.694W 20 JUL 1980 1 0: 1 2: 38.0 62. 629N '148. 776W SL INTEN NAG SM H DIS Q S LOCATION AN 0 C 0 11 M. E N T S (1'111) (Kl'I)(Kl'i) 2.02 60 2.72 82 1. 59 17 1.75 15 3.40 53 3.416 37 0.72 2.08 58 1 .90 13 1 .03 23 1. 59 2 0.89 0.85 5 1. 37 15 1. 04 5 71 1.28 48 1 . 00 15 2.22 65 1. 20 19 0.32 18 1 .25 1. 79 6 1. 25 13 0.56 12 we NO= 13,GhP= 76,01= 32,RMS= .09,ERH= 1.1 ,ERZ= 1.6 we NO= 14,GAP= 271,01= 12,Rl'IS= .14,ERH= 2.2,ERZ= 2.3 we NO= 12,GAP= 208,01= 1 ,RMS= .27,ERH= 2.8,ERZ= 3.0 we NO= B,GAP= 261 ,D1= 21 ,RMS= .20,ERH= 3.5,ERZ= 4.5 we NO= 11 ,GAP= 137,01= 4,RMS= .10,ERH= 1 .9,ERZ= 2.4 WC NO= 12,GAP= 233,01= 13,RMS= .45,ERH= 6.0,ERZ= 11.0 we NO= 6,GAP= 225,01= 15,RMS= .OB,ERH= 2.9,ERZ= 2.5 we NO= 15,GAP= 65,01= 15,RMS= .22,ERH= 2.6,ERZ= 3.5 we NO= 16,GAP= 163,01= 3,RNS= .47,ERH= 3.1 ,ERZ= 7.6 we NO= 10,GAP= 195,01= 12,RMS= .19,ERH= 3.1 ,ERZ= 1.7 WC NO= B,GAP= 247,01= 36,RMS= .16,ERH= 2.4,ERZ= 63.4 t~ NO= 10,GAP= 221 ,Dl= 39,RHS= .29,ERH= 3.4,ERZ= 99.0 DEPTH RESTRICTED DUE TO POOR RESOLUTION. we NO= 9,GAP= 222,D1= 39,RMS= .19,ERH= 2.7,ERZ= 19.9 we NO= 8,GAP= 252,01= 36,RKS= .25,ERH= 6.8,ERZ= 10.5 we NO=: 9,GAP= 225,D1= 39,RMS= .30,ERH= 5.1,ERZ= 55.3 we NO= 9,GAP= 113,D1= 13,RMS= .08,ERH= 2.0,ERZ= 1.8 we NO= 8 ,GAP= 264,01 = 23 ,RI'IS= . 07 ,ERH= 1 . 7 ,ERZ= 1 . 8 we NO= O,GAP= 158,01= 1 ,RMS= .11 ,ERH= 1 .9,ERZ= 3.2 we NO= lO,GAP= 155,01= 13,RMS= .53,ERH= 9.6,ERZ= 9.3 we~~ 12,GAP= 207,01= 2,RMS= .19,ERH= 2.7,ERZ= 1.5 we NO= 7,GAP~ 283,01= 9,RMS= .24,ERH= 6.6,ERZ= 6.6 we NO= ·12,GAP= 206,01= 13,RMS= .23,ERH= 3.0,ERZ= 99.0 we NO= 10,GAP= 178,01= 10,RMS= .16,ERH= 1 .8,ERZ= 6.1 WC NO= lO,GAP= 227,01= 23,RMS= .31 ,ERH= 3.6,ERZ= 13.3 we NO= 8,GAP= 143,01= 4,RMS= .19,ERH= 3.9,ERZ= 4.8 ("") 0 :z -i ....... :z c::: rn 0 52 53 54 55 56 57 58 59 60 61 62 63 65 66 67 68 69 70 71 72 73 74 75 76 LONG SI. ±N'l'EN \ Ml\a sM <H of's < o s 20 JUL 1980 12:33:43.0 62.307N 149.673W 20 JUL 1980 14:50:02.5 62.417N 148.689W 20 JUL 1980 20:01:56.6 62.625N 148.759W 21 JUL 1980 03:31:13.3 62.623N 148.781W 21 JUL 1980 04:10:06.3 62.633N 148.752W 21 JUL 1980 09:10:29.2 62.906N 148.838W 21 JUL 1980 13:12:43.7 62.917N 148.761W 22 JUL 1980 12:32:46.3 62.629N 148.785W 22 JUL 1980 20:26:31.9 62.657N 148.709W 22 JUL 1980 23:26:35.7 62.976N 148.137W 23 JUL 1980 09:51:21.2 62.546N 148.602W 23 JUL 1980 10:07:31,8 62.472N 148.383W 23 JUL 1980 22:24:52.2 62.402N 149.573W 24 JUL 1980 01:10:20.3 62.849N 149.709W 24 JUL 1980 06:57:07.8 62.604N 148,894W 24 JUL 1980 09:51:53.9 62.604N 148.869W 24 JUL 1980 12:27:11.6 62.476N 149.279W 24 JUL 1980 13:32:35.9 62.506N 149.583W 24 JUL 1980 13:51:11.0 62.625N 148.795W 24 JUL 1980 23:50:50.1 62.738N 149.106W 25 JUL 1980 06:19:10.6 63.043N 149.348W 25 JUL 1980 11:38:59.1 62.624N 148.797W 25 JUL 1980 18:18:32.9 62.455N 148.436W 26 JUL 1980 00:26:39.2 62.614N 149.654W 28 JUL 1980 03:31:25.8 62.502N 148.43/JW (MI'I) (KM)(KM) 1. 79 20 1 . 1 a 17 0.01 11 1 .06 11 0.75 9 0.67 11 2. 12 63 0.70 12 0.88 1. 37 7 3.06 55 2.46 50 1. 32 16 2. 31 79 1 • 20 10 1. 03 10 1.26 2.15 65 0.88 10 0.60 3.16 79 0.85 13 1 . 18 25 2.00 15 1.59 27 we NO= 13,GAP= 293,D1= 29,RMS= .30,ERH= 3.6,ERZ= 1.9 we NO= 10,GAP= 227,D1~ 24,RMS= .32,ERH= 3.8,ERZ= 6.4 WC NO= 7,GAP= 153,D1= 5,RMS= .15,ERH= 2.9,ERZ= 4.1 we NO= B,GAP= 152,D1= 4,RMS= .22,ERH= 3.8,ERZ= 6.8 we NO= 7,G~P= 143,D1= 5,RMS= .17,ERH= 4.0,ERZ= 8.4 we NO= 9,GAP= 142,D1= 6,RMS= .12,ERH=. 1 .7,ERZ= 2.7 WC NO= 11 ,GAP= 124,D1= B,RMS= .13,ERH= 1 .9,ERZ= 2.3 we NO= 7,GAP= 140,D1= 4,RMS= .09,ERH= 1 .4,ERZ= 2.9 we NO= 10,GAP= 127,D1= 9,RMS= .32,ERH= 2.1 ,ERZ= 12.8 we NO= 7,GAP= 175,D1= 11 ,RMS= .21 ,ERH= 3.9,ERZ= 8.9 we NO= 5,GAP= 213,D1= 15,RMS= .04,ERH= 19.6,ERZ= 39.4 we NO= 14,GAP= 222,D1= 17,RMS= .73,ERH= 9.0,ERZ= 9.7 we NO= 11 ,GAP= 279,D1= 17,RMS= .33,ERH= 4.4,ERZ= 2.6 we NO= B,GAP= 26B,D1= 18,RMS= .07,ERH= 2.4,ERZ= 2.8 DEPTH RESTRICI'ED DUE TO POOR RESOLUTION. we NO= 9,GAP= 187,D1= 3,RMS= .31 ,ERH= 3.5,ERZ= 6.6 we NO= 10,~ 160,D1= 2,RM6= .34,ERH= 3.2,ERZ= 6.4 we NO= 10,GAP= 229,D1= 12,RMS= .24,ERH= 4.3,ERZ= 99.0 DEPTH RESTRICI'ED DUE TO POOR RESOLUTION. we NO= 11 ,GAP= 270,D1= B,RMS= .29,ERH= 5.2,ERZ= 5.7 we NO= 7,GAP= 248,D1= 36,RMS= .07,ERH= 1 .3,ERZ= 4.3 WC NOr-9,GAP= 152,D1= 19,RM6= .29,ERH= 2.5,ERZ= 99.0 we NO= O,GAP= 249,D1= 25,RMS= .07,ERH= 2.6,ERZ= 3.4 we NO= 7,GAP= 146,D1= 3,RMS= .10,ERH= 1 .4,ERZ= 3.2 we NO= B,GAP= 253,D1= 20,RMS= .11 ,ERH= 2.3,ERZ= 2.8 we NO= 14,GAP= 247,D1= 9,RMS= .30,ERH= 3.0,ERZ= 3.2 we NO= B,GAP= 230,D1= 1B,RMS= .15,ERH= 2.6,ERZ= 3.3 WOODWARD-CLYDE CONSULTANTS -j )> c:J r rn CJ I 1--' n 0 :z -j ...... :z c rn CJ PAGE 4 Cl\T. DATE TIME (GMT) LONG NO. DA'i-110-YEAR HR-i'liN-SEC 71 72 79 80 01 82 83 84 85 86 07 BS 89 90 91 92 93 94 95 96 .sn 98 99 100 101 102 2B JUL 1980 08:09:58.3 62.594N 140.880W 28 JUL 1980 11:34:47.9 63.05-:!N 149.1451-l 29 JUL 1980 08:39:05.4 62.631N 148.778W 29 JUL 1980 12:~4:08.0 62.921N 148.43m 29 JUL !980 14:14:29.7 62.624W 148.796W 31 JUL 1960 06:26:15.1 63.084N 149.602~ 31 JUL 1980 06:417:31 . 9 62. 9801~ 149. 044W 31 JUL 1980 22:07:36.7 62.600N 148.874W 1 AUG 1980 03:09:~3.0 62.898N 148.236W ~UG 1980 05:45:11.9 62.581N 149.004W AUG 1980 14:57:27.9 62.590N 148.890W 2 ~UG 1980 01:40:08.0 62.~37N 148.115W 2 ~UG 1980 06:53:10.~ 62.~69N 147.943W 3 ~UG 1980 10:18:37.5 62.606~ 148.8~7W 3 ~UG 1900 18:59;01.0 62.505W 1~B.917W 3 AUG 1980 19:27:28.1 62.595N 146.92~W 3 ~UG 1980 22:21:37.0 62.614N 148.346W 4 AUG 1980 06:2<1:57.2 62,36BN 148.033~~ ~hUG 1930 13:47:56.2 62.611H 148.B90W ~ ~UG 1900 23:~2:53.5 62.600~ 14B.911W 5 ~UG 1980 01:59:02.7 62.405N 14B,OO~W 5 AUG 1980 03:08:56.3 62.611W 146.902W 5 AUG 1900 05:04:36.5 62.604N 14S.BB6W 5 AUG 1980 06:01:20.2 62.910N 149.340W 5 AUG 1980 09:10:12.7 62.609N 148.919W S AUG 19BO 12:59:21.1 63.119N 1~B.520W SL INTEN NAG SM H DIS 0 S LOCATION AN D COMMENTS <MM) (KN)(KM) 1 .42 1 . 21 0.90 0.89 0.78 2.1132 2.00 0.97 3.43 2. 71 0.59 1 • 23 2.21 1 . 34l 1. 07 0.96 0.92 1 • 3.@ 0.78 1.17 2.06 0.89 0.70 1 .98 0.67 10 17 11 1 3 8El 71 SfJ 11 14 45 55 16 141 15 16 15 15 50 16 Hi WC N~ 10,GAP= 190,D1 3 ,ID'IS;. .35,ERH= 3.6,ERZ= 6.9 WC NO~ 7,GAP= 238,D1= 17,RMS= .29,ERH= 6.0,ERZ= 11.7 WC ND= O,GAP= 140,D1= ~,RNS= .13,ERH= 2.2,ERZ= 4.3 h~ He= 7,b~P= 119,D1= 19,RMS= .10,ERH= 1 .2,ZRZ= 11 ,q WC ~ 7,GAP= 147,01= J,RMS= .OB,ERH= 1 .3,ERZ= 2.5 WC NO= 12,GAP= 271 ,D1= l4,RMS= .09,Erui= 2.1 ,ERZ= 2.1 WC ~ 13,GAP= 173,D1= S,RMS= .l2,ERH= 1 .G,ERZ= 1.8 WC NO= 9,GAP= 221 ,D1= 2,RHS= .32,ERH= ~.1 ,ERZ= 5.9 we ~XF 12,GAP= 115,01= 16,RKS= .07,ERH= 1 .2,ERZ= 1.5 WC NO= 13,GAP= 167,D1= 9,RNS= .09,ERH= 1.2,ERZ= 1.8 WC NO= 1.~~P= 191 ,D1= 3,RMS= .50,ERH= 6.5,ERZ= 14.0 we NO= 7,GThP= 297,01= 13,RMS= .07,ERH= 1 .9,ERZ= 1.5 ~C NO= 1~,GAP= 287,D1= 13,R~S= .2B,ERH: 3.7,ERZ= 3.4 t'X: NO= 13 ,Gi!P= 150,01 = 1 ,FikiS= • 14 ,ERH= 1 • 7 ,ERZ= 2. 1 we~~ 16,GAP= 159,01= ~.RnS= .37,ERH= 2.4,ERZ= 5.9 WC NO= 12,C~ 163,D1= 4,RMS= .39,ERH= 2.6,ERZ= 7.0 WC NO= B,~P= 177,D1= O,RNS= .32,ERH= 4.8,ERZ= 7.3 we NO= 12,GAP= 29B,D1= 21 ,RNS= .11 ,ERH~ 1 .4,ERZ= 1.0 WC NO= 9,G~P= 157,01= 2,RMS= .43,ERH= 4.3,ERZ= 8.7 ~~NO= 12,~P= 189,01= 4,RMS= .41 ,ERH= 4.1 ,ERZ= 7.6 WC NO= 11 ,G~P= 2BO,D1= 18,RMS= .30,ERH= 4.9,ERZ= 5.6 WC NO= S,G~P= 185,D1= 3,RMS= .29,ERH= 4.7,ERZ= 7.2 WC NO= 10,GA~ 1B7,D1= 2,RMS= .27,ERH= 3.3,ERZ= 5.7 WC ~ 12,GAP= 223,01= 22,RAS= .33,ERH= 3.6,ERZ= 0.1 WC NO=. 9,GAP= 204,D1 4,RNS= .24,ERH= 2.7,ERZ= 5.1 n 0 :z -; ...... ;z c rn 0 ----------------------------------------------------------------------------------------------------------------------------------~~ 103 104 105 106 1 07 108 109 11 0 111 11 2 113 1 15 116 117 118 119 120 1 21 122 123 124 125 126 127 5 AUG 1980 16:15:1~.1 62.598N 148.895W 6 AUG 1980 10:00:53.1 63.016N 148.766W 6 AUG 1980 11:36:50.9 62.609N 148.879W 6 AUG 1980 15:31:11 .B 62.B52W 1~B.535W 6 AUG 1980 23:50:1~.1 62.859N 1~9.306W 1 nUG 1980 07:55:00.8 62.604N 148.904W 7 ~UG 1980 09:50:30.9 62.63SN 148.865W 7 AUG 1980 14:38:55.5 62.607N 148.899W S gOG 1900 04:59:36.6 62.613N 1~8.878W Gl l'IUG 1980 07:39:(!S.fl 62.60BN 1<'J8.865W 8 ~L~ 1980 09:41:19.1 62.603N 1~9.5~7W Ell ~UG 1980 12:13:00.2 62.4\BON 148.5191-J e nuc 1seo 15:51:21.6 62.624~ 148.B74W 9 Au~ 1980 01:21':11.6. 62.B?7N 14B.987W 9 ~UG 19BO 06:16:39.2 63.129N 14B.525W 10 AUG 1990 14:28:38.9 62.751W 14B.2~3W 10 ~UG 1980 16:23:~5.5 63.035N 149.255W 11 AUG 1980 11:41:02.8 62.809N 148.364W 11 AUG 1980 12:36:31.9 62.309N 1~8.~28W 12 AUG 1980 02:15:07.0 62.370N 148.110W 12 ~UG 1900 06:25:45.5 62.B16N 149.338W 12 ~UG 1980 17:~6:46.6 62.427N 1~8.259W 12 AUG 1980 21:2~:35.7 62.B26N 1~B.326W 12 ~UG 1960 22:54:57.) 62.351N 150.1B2W 13 nuc 1soo oo:os:~7.3 62.791N 148.215W 1 . 12 1 • 32 1. 07 0.59 1 .90 0.?0 1.06 0.92 0.71' 1 • 15 1 • 01 1 • 31 1 .00 1. 46 1.11 1. 90 1.51 0.01 1. 51.! 1 • 81 1. 4\8 1. 73 1 .85 3.26 11 15 2 72 14 17 16 15 27 17 16 6 60 13 2 45 16 64 19 WC NO= 14,GAP-162,01= 3,RMS= .47,ERH= 2.7,ERZ= 7.8 WC NO= 13 ,GAP-179 ,D1"' 1 0 ,RMS= .41 ,ERH= 2.8,ERZ= 9.2 WC NO=: 14,GAP= 1BS,D1 2,RMS= .~4,ERH= 2.9,ERZ= 7.7 WC ~~ 10,GAP= 94,01= 22,RMS= .13,ERH= .7,ERZ= 23.8 DEPTH RESTRICTED DUE TO POOR RESOLUTION. ~~ ~ 11 ,GnP= 113,01= 17,RMS= .12,ERH= 2.5,ERZ= 2.0 WC NO= 7 ,GAP= 197 ,D1 = 3 ,rulS= . 17 ,ERH= 2. 8 ,ERZ= 5. 1 WC NO= B,GAP= 155,01= 2,RMS= .30,ERH= 4.3,ERZ= 7.4 WC NO= 11,GAP= 186,01= 3,RMS= .27,ERH~ 2.6,ERZ= 5.1 WC NO= 13,GAP= 184,01= 2,RMS= .36,ERH= 2.5,ERZ= 6.4 we i'OCJ= 12 ,Gru?= 219 ,o1 = 1 ,rum= • 39 ,ERH= 3. 4 ,ERZ= 6. s WC tiD= 10,GnP= 247,01= 11,RMS= .39,ERH= 6.4,ERZ= 16.2 WC ~ 14,GAP= 22~,01= 23,RMS= .32,ERH= 3.5,ERZ= 4.7 WC NO= 11 ,GAP= 188,01= 2,RMS= .30,ERH= 2.7,ERZ= 5.? WC NO= 13,~P= 100,01= 9,RMS= .33,ERH= 1.8,ERZ= 5.1 WC N~ 7,~P= 253,01= l7,RMS= ,17,ERH= 2.B,ERZ= 10.2 W~ we= 13,G~P= 105,01= 1S,RKS= .13,ERH= 2.0,ERZ= 2.2 ~~NO= e,~P= 2~1 ,D1= 42,~S= .28,ERH= 4.2,ERZ= 17.3 W'C NO= S,GAP= 14<ll,D1= 21,IDIS= .OO,ERH= .S,ERZ= 15.1 DEPTH RESTRICTED DUE TO PODR RESOLUTION. WC NO= 10,GAP= 290,01= 32,RMS= .17,ERH= 2.8,ERZ= 3.8 WC NO= 8,~ 296,D1= 21 ,RMS= ,06,ERH= 1 .2,ERZ= 1.1 WC NO= 13,GAP= 169,01= 2,RRS= .26,ERH= 1.fl,ERZ= 3.0 we NO= 12,~ 265,01"' 16,RNS= :21,ERH=o 2.7,ERZ= 3.3 WC NO= 9,GAP= 135,D1= 19,RMS= .12,&~= 2.5,ERZ= 2.5 WC NO= 12,GThP= 31B,D1= 43,RMS= .23,ERH= 3.2,ERZ= 1.7 WC ~~ 13,Gl~ 97,01= 1~,RMS= .23,ERH= 2.0,ERZ= 3.6 WOODWARD-CLYDE CONSULTANTS 0 I ...... (""") o z -1 ....... :z c::: rtl CJ PAGE 6 CAT. NO. 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 DATE TIME(GMT) LAT LONG DAY-MO-YEAR HR-MIN-·SEC 13 AUG 1980 03:32:59.1 62.662N 148.830W 13 AUG 1980 09:01:53.7 62.469N 149.928W 13 AUG 1980 14:43:58.1 62.618N 148.867W 13 AUG 1980 20:20:15.3 62.966N 149.253W 13 AUG 1980 21:01:48.5 62.873N 148.258W 14 AUG 1980 20:40:17.7 63.290N 149.497W 14 AUG 1980 21:33:02.0 62.821N 149.129W 15 AUG 1980 00:55:29.4 62.410N 148.978W 15 AUG 1980 13:13:38.4 62.447N 148.186W 15 AUG 1980 18:36:09.1 62.436N 148.314W 16 AUG 1980 11:23:28.1 62.871N 148.361W 16 AUG 1980 17:56:02.2 63.276N 148.497W 16 AUG 1980 18:36:25.7 62.891N 149.202W 16 AUG 1980 21:06:48.8 62.599N 148.890W 17 AUG 1980 13:32:54.9 62.365N 148.311W 17 AUG 1980 14:54:41.9 62.369N 149.635W 18 AUG 1980 01:41:23.5 63.019N 148.481W 18 AUG 1980 15:39:07.6 63.098N 148.915W 18 AUG 1980 17:01:27.1 62.497N 148.987W 18 AUG 1980 23:28:03.1 63.120N 148.845W 19 AUG 1980 00:25:37.2 62.640N 148.831W 19 AUG 1980 01:19:29.1 62.505N 149.300W 19 AUG 1980 10:51:59.6 62.528N 149.148W 20 AUG 1980 05:34:49.0 62.451N 148.663W 20 AUG 1980 07:14:45.9 62.406N 148.248W SL INTEN (MM) MAG SM H DIS Q S (KM)(KM) L 0 C A T I 0 N A N D C 0 M M E N T S 2.03 57 1 .90 19 0.70 14 2.03 71 0.44 64 1. 43 0.67 17 1. 34 51 3.50 56 1 . 01 51 1 . 71 60 1. 78 18 2.27 63 0.65 18 2.36 48 1 .65 16 2.15 1 .56 14 0.96 21 0.92 12 0.85 16 1 . 31 11 1. 68 15 1 . 31 15 3.40 47 we NO= 14,GAP= 84,D1= 5,RMS= .15,ERH= 1 .6,ERZ= 2.1 we NO= 14,GAP= 295,D1= 26,RMS= .29,ERH= 3.3,ERZ= 1.9 we NO= 10,GAP= 170,D1= 1 ,RI'IS= .40,ERH= 3.8,ERZ= 7.6 we NO= 11 ,GAP= 172,D1= 16,RMS= .16,ERH= 2.6,ERZ= 2.7 we NO= 8,GAP= 101 ,D1= 16,RMS= .04,ERH= .9,ERZ= 1 .6 we NO= 7,GAP= 287,D1= 37,RMS= .18,ERH= 3.7,ERZ= 99.0 DEPTH·RESTRICTED DUE TO POOR RESOLUTION. we NO= 11 ,GAP= 127,D1= 10,RMS= .35,ERH= 2.9,ERZ= 5.8 we NO= 9,GAP= 244,D1= 24,RMS= .14,ERH~ 2.6,ERZ= 2.9 we NO= 11 ,GAP= 262,D1= 13,RMS= .12,ERH= 2.2,ERZ= 3.2 we NO= 9,GAP= 267,D1= 17,RMS= .08,ERH= 1 .5,ERZ= 1.6 we NO= 8,GAP= 157,D1= 21 ,RMS= .14,ERH= 2.9,ERZ= 3.2 we NO= '10,GAP= 301 ,D1= 28,RI'IS= .26,ERH= 3.7,ERZ= 2.2 we NO= 15,GAP= 135,D1= 16,RMS= .26,ERH= 2.8,ERZ= 3.7 we NO= B,GAP= 189,D1= 3,RMS= .34,ERH= 3.6,ERZ= 4.9 we NO= 14,GAP= 263,D1= 24,RMS= .18,ERH= 2.7,ERZ= 2.7 we NO= 10,GAP= 287,D1= 22,RMS= .32,ERH= 5.0,ERZ= 1.0 we NO= 9,GAP= 167,D1= 14,RMS= .12,ERH= 1 .7,ERZ= 97.6 WC NO= 8,GAP= 237,D1= 17,RMS= .24,ERH= 4.1 ,ERZ= 9.2 we NO= 8,GAP= 248,D1= 15,RMS= .28,ERH= 9.2,ERZ= 5.1 we NO= 9,GAP= 218,D1= 19,RMS= .27,ERH= 3.7,ERZ= 9.6 we NO= 8,GAP= 115,D1= 3,RMS= .40,ERH= 9.6,ERZ= 7.8 we NO= 14,GAP= 215,D1= 10,RMS= .39,ERH= 3.7,ERZ= 6.1 we NO= 16,GAP= 191 ,D1= 16,RMS= .45,ERH= 3.1 ,ERZ= 5.2 we NO= 8,GAP= 264,D1= 21 ,RMS= .16,ERH= 2.4,ERZ= 3.7 we NO= 14,GAP= 261 ,D1= 18,RMS= .60,ERH= 10.0,ERZ= 9.7 WOODWARD-CLYDE CONSULTANTS CJ I 1--' 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 160 169 170 171 172 173 174 175 176 177 20 AUG 1980 13:41:47.8 62.962N 149.86UW 20 AUG 1980 23:43:35.2 62.416N 148.236W 21 nUG 1980 13:01:42.5 62.596N 148.900W 21 AUG 1980 14:45:20.5 62.498N 149.012W 21 AUG 1980 16:12:01.9 62.923N 149.677W 21 AUG 1980 17:04:5~.5 62.942N 148.564W 22 nUG 19BO 13:24:12.7 62.9lSN 150.107W 23 ~UG 1900 22:00:05.0 62.954N 1~9.300W 24 ThUG 1980 01:50:34.6 62.493N 140.926W 24 ~UG 1980 0~:29:43.~ 62.619N 140.888W 24 aUG 1900 04:30:51.5 62.626N 148.863H 24 AUG 19130 12:44:37.1 62.961N 149.14l1W 24 A~~ 1980 14:00:45.7 52.433~ 148.657W 2~ AUG 1980 16:23:06.1 62,901W 146.572W 24 AUG 1980 22:36:26.5 62.738N 148.83SH 25 ~UG 1900 04:45:35.3 62.895N 149.462W 25 AUG 1980 10:06:50.5 52.600!.'1 Hl8.El97\l 25 ~UG 1980 12:16:~0.6 62.611!.'1 148.893W 25 AUG 1980 16:17:09.~ 63.130N 149.304W 25 AUG 1900 20:10:06.6 53.070N 1~9.158W 27 AUG 1980 00:15:16.0 62.42flN 148.383W 27 AUG 1960 01:10:50.1 62.906N 148.870W 27 AUG 1960 09:10:13.1 62.839!.'1 148.388W 27 AUG 1980 10:20:31.7 62.656N 149.191W 27 AUG 1980 15:40:32.8 62.490N 149.036W 1. 70 2.20 1. 46 0.37 1. 70 0.72 1.62 1 . 06 1.15 1 .65 1. 06 2.2<2 1. 79 0.01 1. 31 2.53 1. 06 1. 04 1.31 1.40 1 .87 1. 46 1 .68 1 .48 1 • 18 16 43 15 20 59 17 10 19 17 16 76 45 2 59 11 15 16 17 65 150 61 18 WC NC= 14,GAP= 2B5,D1= 15,RMS= .32,ERH= 3.5,ERZ= 1.8 WC ~ B,GAP= 282,01= 17,RMS= .lO,ERH= 2.1 ,ERZ= 2.2 WC NO= 15,GAP= 163,D1= 3,RMS= .47,ERH= 3.3,ERZ= 7.5 WC NO= 11 ,GAP= 223,01= 15,RMS= .34,ERH= 5.7,ERZ= 2.9 WC NO= 10,GAP= 141,D1= 28,RMS= .14,ERH= 2.3,ERZ= 3.1 we~ 8,GAP= 1~1 ,01= 17,RMS= .77,ERH= 5.0,ERZ= 99.0 DEPTH RESTRICTED DUE TO POOR RESOLUTION. WC NO= 12,GAP= 303,D1= 40,RNS= .13,ERH= 1.5,ERZ= 1.1 we NO= 10,GAP= 229,D1= 33,RMS= .47,ERH= 12.3,ERZ= 10.5 WC NO= B,GAP= 295,01= 14,RMS= .22,ERH= 3.9,ERZ= 3.5 we NO= 12,GAP= 180,01= 2,RMS= .30,ERH= 2.7,ERZ= 3.1 WC NO= 12,GAP= 129,D1= 2,RMS= ,38,ERH= 3.0,ERZ= 5.3 we NO= 8,GAP= 167,D1= 21 ,RNS= .20,ERH= 6.3,ERZ= 4.5 WC h~ 10,GAP= 236,01= 23,RMS= .15,ERH= 2.6,ERZ= 2.3 WC "~ 8,GAP= 201 ,01= 25,RAS= .12,ERH= 1.1 ,ERZ= 30.1 DEPI'H RESTRICTED DUE TO POOR RESOLUTION. WC NO; 8,GAP= 185,01= ~3,RMS= .07,ERH= 1 .4,ERZ= 1.9 WC WO= l&,GAP= 127,D1= 9,RMS= .15,ERH= 2.4,ERZ= 2.1 we NO= 11 ,GAP= 188,01= 3,RMS= .47,ERH= 5.1 ,ERZ= 8.7 we NO= 12,GAP= 105,D1= 2,RMS= .39,ERH= 3.0,ERZ= 7.0 WC NO= 12,Gil.P= 244,01= 23,RM= .24,ERH= 2.9,ERZ= 2.6 we NO= 9,GAP= 213,01= 24,RMS= .12,ERH= 2.1,ERZ= 6.5 ~NO= 13,GAP= 235,01= 20,RMS= .09,ERH= 1 .2,ERZ= 1.4 WC NO= 6,GAP= 143,D1= 35,RHS= .06,ERH= 1.1 ,ERZ= 1.6 lie NO= 12,GAP= 96,01"' 23,RNS= .15,ERH= L6,ERZ= 2.6 WC NO= B,GAP= 179,01 22,RMS= .20,ERH= 5.4,ERZ= 4.9 \:K: NO= Hl ,GAP= 203,01 = 1 3 ,RMS= . 34 ,ERH= 3. 1 , ERZ= 3. 6 WOODWARD-CLYDE CONSULTANTS --i )> c:p r rn 0 I 1-' n 0 ::z --i ...... ::z c: rn 0 PAGE 8 CAT. DATE TIME(GHT) !AT LONG SL INTEN 1'11\G SN H DIS 1J S LOCl'ITION l\ N D COrii'lENTS NO. OAY-00-YEAR HR-NIN-SEC 178 27 AUG 1980 10:16:31.2 62.~95~ 149.019~ 179 27 ~UG 1980 20:3~:2~.1 62.483N 148.933W 180 28 ~UG 1980 11:30:04.2 62.592N 149.099W 161 182 183 104 185 186 187 188 199 190 191 192 193 19<2 195 196 197 198 199 200 201 202 20 ~UG 1980 19:03:42.6 62,506N 149.011W 29 ~UG 1980 09:12:28.2 62.496H 148.9~2W 29 ~UG 1980 11:56:49.7 62.500W 14B.99SW 29 AUG 1980 19:12:10.1 62.497N 1<!8.971~ 29 AUG 1980 19:55:43.6 62.~7BN 148.960W 30 AUG 1980 00:54:36.5 62.590H 149.073W 30 AUG 1980 06:33:17.3 62.616N 14B.B88W 30 ~UG 1980 08:17:33.9 62.505N 1~8.960W JO ~UG 1980 09:05:18.1 62.509N 143.960W 30 AUG 1980 11:13:15.4 62.519N 149.296W 30 AUG 1930 15:39:~8.6 62.J~1N 148.279W 30 AUG 1980 16:15:08.0 62.516N 14B.B59W 31 ~UG 1980 10:49:53.5 62.48~N 149.010W 31 AUG 1980 10:52:53.0 62.487N 14B.942M 31 ~UG 1960 15:01:30.7 62.731W 149.769W 31 ~UG 1980 22:21:12.5 62.497N 148.937W SEP 1980 01:49:29.8 62.895N 149.020W SEP 1980 19:33:08.5 62.351N 148.191W 2 SEP 1980 05:18:11.4 62.471N 149.042W 2 SEP 1980 09:39:23.7 62.477N 149.011W 2 SEP 1980 09:48:50.7 62.719N 148.327W 2 SEP 1980 13:28:09.0 62.490N 149.005W (i'lM) (KM) (Kf'l.) 0.96 1. 29 1 . 53 0.59 1 • 09 1. 20 1. 26 1.Hl 1 .67 1. 70 0.85 0.92 1. 09 1.43 0.65 1 . 12 0.61 1 • 40 0.75 0.85 1 .62 1 . 23 1 .56 2.53 0.77 21 21 55 21 19 19 18 19 56 16 19 10 10 46 15 19 19 19 17 12 15 16 51 19 WC ~ B,GAP= 199,01 12,RMS= .26,ERH= 6.0,ERZ= 2.5 DEPTH RESTRICTED DUE TO POOR RESOLUTION. WC NO= lO,GAP= 227,01= 12,RMS= .16,ERH= 2.0,ERZ= 1.9 ~NO= 13,GAP= 163,01= 11 ,RMS= .lB,ERH= 2.3,ERZ= 2.7 WC NO= B ,CAP= 192 ,Dl= 11 ,RM&:= • 34 ,ERH= 7. 2 ,ERZ= 5.1 WC WO= 10,GaP= 264,01: lO,RNS= .23,ERH= 2.6,ERZ= 2.8 WC NO= lO,GAP= 220,01= 11 ,RMS= .45,ERH= 5.6,ERZ= 5.5 WC NO= lO,Gl'IP= 213,01= 11 ,RMS= .30,ERH= 3.6,ERZ= 3.5 WC NO= B,CJIP= 277,01= 11 ,RMS= .06,ERH= .9,ERZ= .9 WC NO= 14,GAP= 161 ,01= lO,RMS= .21,ERH= 2.5,ERZ= 3.1 WC NO= 15,GAP= 108,01 4,RMS= .4B,ERH= 2.B,ERZ= 5.0 WC NO= 11 ,GAP= 212,01= lO,RMS= .24.ERH~ 2.9,ERZ= 2.7 WC NO= 12,GAP= 210,01= 9,RMS= .2B,ERH= 3.1 ,ERZ= 2.9 WC NO= 11 ,GAP= 216,01= 22,RMS= .41 ,ERH= 4.6,ERZ= 9.8 WC NO= 10,GAP= 273,01= 25,Rl'IS= .09,'ERH= 1 .6,ERZ= 1.5 WC NO= 9 ,GAP= 120 ,Dl = 4 ,RMS= . 32 ,ERH= 4. 0, ERZ= 5 . .:! WC NO= 16,Gl'!.P= 204,01= 13,Rl'IS= .32,ERH= 2.3,ERZ= 3.0 WC NO= lO,GAP= 253,01= 10,RMS= .19,ERH= 2.7,ERZ= 2.2 WC NO= B,~P= 265,01= 9,RMS= .11 ,ERH= 1 .8,ERZ= 1.1 we~ lO,GThP= 2~7,D1= lO,RMS= .19,ERH= 2.3,ERZ= 2.9 WC NO= 13,~P= 141 ,Dl= 6,RMS= .31 ,ERH= 2.4,ERZ= 3.1 WC WO= 12,GAP= 279,01= 23,Rl'IS= .05,ERH= .9,ERZ= .8 we NO= 17,GAP= 214,01= 15,RMS= .43,ERH= 3.8,ERZ= 5.6 WC NO= lO,GAP= 209,01= 13,RMS= .41 ,ERH= 3.2,ERZ= 4.0 WC NO= 11 ,GAP= 92,D1 21 ,RMS= .OS,ERH= 1 .4,ERZ= 2.6 WC NO= 14,G~P= 200,01= 12,RMS= .33,EP~= 2.8,ERZ= 3.4 ("""} 0 :z -1 ...... :z c ITl 0 GAT. Ol\TE NO. DAY-MO-YEAR 203 204 205 206 207 209 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 2 SEP 1900 23:12:08.2 62.068N 1~8.626W 3 SEP 1980 01:03:52.9 62.931N 148.132W 3 SEP 1980 05:53:34.6 62.619N 148.791W 3 SEP 1900 12:13:10.2 62.630N 149.45UW 3 SEP 1980 1~:33:08.0 62.490N 1~0.933W 3 SEP 1980 14:33:10.7 62.513N 1~8.942W 3 SEP 1980 15:06:44.0 62.95BN 148.940W 4 SEP 1980 06:43:10.5 62.521N 149.015W 5 SEP 1980 07:51:50.7 62.919N H9.040W 5 SEP 1980 12:00:13.4 63.070N 148.577W 6 SEP 1900 03:41:26.1 62.663N 148.943W 6 SEP 1980 16:15:37.8 52.~91N 149,005W 7 SEP 1900 11:28:34.3 62.882N 148.135W 7 SEP 1900 14:37:14.6 62.492H 148.920W 8 SEP 1900 06:40:34.9 62.929N 1~fl.773W 8 SEP 1980 21:52:57.4 62.713N 14B.394W 8 SEP 1980 23:29:29.1 62.846N 14lL462W 9 SEP 1980 22:48:33.6 62.954N 148.687W 10 SEP 1980 14:09:08.5 62.486N 14B.980W 10 SEP 1980 16:48:23.7 62.725N 148.252W 10 SEP 1980 22:43:22.5 62.732N 140.252~J 10 SEP 1980 23:17:19.1 62.685N 149.370W 11 SEP 1980. 01:52:22.8 62.631N 149.476W 11 SEP 1900 03:07:51.8 62.B64N 148.193W 11 SEP 1980 11 :40:38.~ 62.513N 148.969W 11 SEP 1980 12:09:53.0 62.862N 148.153W 1 .96 1.56 0.61 1. 98 1. 24 1 • 241 1 • 00 0.59 0.96 1 • 40 1 . 40 1 • 43 0. 61 1. 76 1 • 40 1 • 43 1 • 81 1 • 041 0.93 1 . 12 1 • 01 1 • oo 3.37 1 .56 2.68 16 62 61 19 16 1 5 10 6B 61 Hl 5S Hl 613 50 62 71 19 35 33 1 3 58 52 60 WC NO= 14,GAP= 121,01 6,RMS= .27,ERH= 1 .7,ERZ= 2.9 WC ~n= 7,GA~ 158,01 14,RMS= .15,ERH= 5.9,ERZ= 4.0 WC NO= 9,GAP= 120,01 6,RMS= .15,ERR= 1.6,ERZ= 3.1 WC NO= 13,GAP= 192,D1= 11 ,RMS= .15,ERH= 2.2,ERZ= 2.3 WC ~ 10,GAP= 250,01= lO,RNS= .17,ERH= 2.9,ERZ= 2.0 WC NO= 1D,GA~ 239,01= 8,RMS= WC NO= 7,GAP= 262,01= 9,lli1S= .16,ERH= 4.7,ERZ= 3.1 WC NO= 11 ,GAP= 104,01= 10,RMS= .46,ERH= 4.4,ERZ= 5.5 WC NO= 12,~AP= 194,01= B,RMS= .77,ERH= 6.B,ERZ= 13.7 WC NO= 9,GAP= 222,01 18,RMS= .07,ERH= 1 .7,ERZ~ 1.5 ~~NO= 16,GAP= 115,01= 10,RMS= .19,ERH= 1.9,ERZ= 2.6 WC ~ 17,GAP= 200,01 12,RMS= .42,ERH= 2.9,ERZ= 4.0 WC ~ 10,GA~ 133,01= 11 ,RMS= .12,ERH= 2.0,ERZ= 2.2 we~ 10,GAP= 248,01= 10,RHS= .14,ERH= 2.0,ERZ= 1.7 we~= ?,GAP= 147,01= 9,RMS= .10,ERH= 2.2,ERZ= 2.3 WC NO= 12,GAP= 128,01= 23,RMS= .09,ERH= 1.0,ERZ= 1.5 WC NO= 10,GAP= 128,01 23,RMS= .14,ERH= 2.6,ERZ= 2.7 WC NO= 9,GA~ 152,01= 14,RMS= .13,ERH= 3.6,ERZ= 3.2 WC NO= 13,GAP= 200,01= 12,RMS= ,30,ERH= J.O,ERZ= 3.2 WC NO= O,GAP= 138,01 20,RMS= .11 ,ERH= 1 .7,ERZ= 2.8 WC ~ 10.Q\P= 131 ,D1= 19,RMS= .11,ERH= 1 .2,ERZ= 2.3 WC NO= 12,GAP= 159,01= 13,RRS= .26,ERH= 1 .5,ERZ= 99.0 WC NO= 12,GAP= 197,01= 10,RMS= .26,ERH= 2.4,ERZ= 3.7 WC NO= 13,GAP= 110,01 13,RHS= .21 ,ERH= 2.B,ERZ= 3.5 WC NO= 16,GAP= 182,01= 9,RMS= .19,ERH= 2.D,ERZ= 2.3 WC NO~ 15,GAP= 116,01= 11 ,RMS= .11 ,ERH= 1.1 ,ERZ= 1.4 WOODWARD-CLYDE CONSULTANTS n 0 :z ---j 1--i :z c: rn 0 PAGE 10 CiiT. NO. 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 245 246 247 248 249 250 251 252 253 254 DATE TIME(GMT) !AT VJNG DAY-AO-YEAR HR-HIN-SEC 11 SEP 1980 14:13:30.6 62.844N 149.408H 11 SEP 1980 21 :15:3~.6 62.583N 14B.757W 12 9EP 1900 03:37:45.9 62.842N 148.9B2W 12 SEP 1960 04:27:59.4 62.779N 149.432W 12 SEP 1980 05:48:35.6 62.587N 149.397W 12 SEP 1980 20:27:21.2 62.592N 14B.903W 14 SEP 1980 00:19:28.6 62.517N 149.619W 14 SEP 1980 17:57:15.7 62.804N 149.2B3W 15 SEP 1980 23:02:45.0 62.776N 148.35GW 16 SEP 1980 01:19:53.4 52.608N 148.889H 17 SEP 1980 02:57:31.8 62.662N 1~9.551W 11 SEP 1980 03:30:05.9 62.971N 149.152U 11 SEP 1980 15:19:14.5 62.759N 149.349~1 11 SEP 1980 19:56:57.8 63.056N 1<39.225H 10 SEP 1980 08: 33: 12. 6' 62. 490N 1 138. 4401~ 18 SEP 1980 14:52:44.7 62.833N 14B.615W 19 SEP 1980 11:09:03.3 62.B05N 149.576W 20 SEP 1980 10:50:16.7 62.964N 1~9.396W 21 SEP 1980 06:59:06.1 62.829W 148.408W 21 SEP 1980 09:41:52.8 62.709N 140.664W 21 SEP 1980 13:47:52.8 62.375N 148.774W 21 SEP 1980 23:13:07.8 62.607N 149.5~1W 22 SEP 1980 10:10:1~.2 62.977N 149.020W 22 SEP 1980 11:49:10.0 62.619N 1~9.530W 22 SEP 1980 21:59:52.8 62.~13N 148.760W 23 SEP 19BO 03:42:01.5 62.67~N 149.~17W SL INTEN (l'lM) MAG SN H DIS Q S (KM)(KM) L 0 C A T I 0 l:l 1l N 0 C 0 M M E N T S 1 . 03 15 1 . 51 56 1 . 60 63 1 .70 15 1 . 09 0.50 16 2.3~ 60 0.39 2.43 66 0.70 14 1 .79 15 1 • 0 3 HI 0.65 13 1 . Jll 1 1. 29 23 2.11 60 1 .15 12 0.05 10 1.26 67 2.66 53 1 • ll2 48 0.02 10 1 . 31 11 B 1 . '5 20 1 .oo 62 WC NO= 11 ,GAP= 117,01= 5,RMS= .21 ,ERH= 1 .7,ERZ= 2.5 WC ~ 14,GAP= 90,01= 6,RMS= .09,ERH= 1 .O,ERZ= 1.3 WC NO; 12,GAP= 117,01= G,RMS= .17,ERH= 2.6,ERZ= 3.0 WC ~ 19,G~P= 118,D1= B,RMS= .36,ERH= 2.0,ERZ= 3.5 WC NO= 12,GAP= 224,01= 16,RMS= .27,ERH= 2.6,ERZ= 99.0· WC ~ 10,GAP= 134,01= 2,RRS= .30,ERH= 2.4,ERZ= 3,6 WC N~ 6,GAP= 282,D1= 20,RMS= .13,ERH= S.B,ERZ= 4.6 OC NO= 6,GAP= 105,01= 21 ,RMS= ,05,ERH= .1 ,ERZ"' 35. ·7 WC N~ 15,GAP= 80,01= 22,RMS= .14,ERH= 1 .5,ERZ= 1.9 WC NO= 13,GAP= 127,01= 18,RMS= .25,ERH= 1 .6,ERZ= 4.7 WC NO= 13,GAP= 198,01= 5,RMS= .20,ERH= 1 .B,ERZ= 3.2 WC NO= 9,GAP= 172,01= 16,RMS= .20,ERH= 3.4,ERZ= 5.2 WC NO= ?,GAP= 17B,D1= 15,RMS= .19,ERH= 4.B,ERZ= 5.8 WC NO= 16,GAP= 212,01 20,RMS= .25,ERH= 1 .B,ERZ= 6.8 WC NO= 13,GAP= 190,01= 17,RMS~ .17,ERH= 1 .4,ERZ~ .9 tie NO= 7,~~P= 1~9,D1= 16,RMS= .2~,ERH= 5.3,ERZ= 6.1 WC NO= S,GAP= 2~8,01= 13,RMS= .19,ERH= 2.6,ERZ= 3.6 OC NO= ?,GAP= 205,01= B,RMS= .1S,ERH= 2.1 ,ERZ= 3.7 WC NO= 9,GAP= 167,01= 24,RMS= .06,ERH= 1 .B,ERZ= 1.3 we NO= 16 ,GAP= B<J ,01 = 1 4 ,RMS= . 17, ERH= 1 . 4 ,ERZ= 2 ') ~VC NO= 13,GAP= 270,D1= 9,RMS= .15,ERH= 2.0,ERZ= 2.3 WC WOe B,GAP= 266,01= 10,RMS= .1 0 ,ERH= 1 .6 ,ERZ= 2 ') . ~ WC NO= 11 ,GAP= 171 ,01= 12,RMS= .30,ERH= 2.1 ,ERZ= 4. l WC NO= 13,GAP= 219,01= 9,RMS= .17,ERH= 1 .7,ERZ= 3.0 WC NO= 14,GAP= 26<J,D1 5,RMS= .22,ERH= 2.1,ERZ= 1.4 WC NO= 11,GAJ>.; 171,01= lO,Rl'lS= .24,ERH= J.B,ERZ= 3.7 -l p co r rn 0 I ,_.. n 0 z -l ........ z c:: rn CJ Cl\T. Dl\TE TIME ( G.M'r) Ll\T LONG SL INTEN MAG SM H DIS Q c• Q L 0 C A •r I ON AND COM1'\Et1T s llO. DAY-/10-YEJ\R IIH-MIN-SEC (/1M) (Kl'l) ( KM) -------------------------------------------------------------------------------------------------------------·-·--------------------------1 p 255 23 SEP 1980 23:51:58.3 62.972N 148.359W 1 .96 10 we NO= l5,GI\P= 126,01= 12,11MS= . 30 ,ERH= 1 . 7 ,ERZ= CD 4.6 ' rrl 256 24 SEP 1980 00:34:32.2 62.671N 148.944W 1 .96 60 we NO= IO,GAP= 116,01= 23,RMS= .10,ERH= 1 .6,ERZ= ?..1 CJ I 1-' 257 24 SEP 1980 05:15:55.3 62.975N 148.3471'1 1 .56 10 we NO= B,Gl\P= 143,01= 11 ,RMS= .13,ERH= 1.1 ,ERZ= 3.2 n 258 24 SEP 1980 05:18:16.2 62.307N 148.148W 1 .68 18 we NO= 13 ,GAP= 288,01= 36,RMS= . 25 ,ERH= 2.9,ERZ= 1 .6 C> :z: -1 259 24 SEP 1980 07:50:04.7 62.525N 149.176W I .48 54 we NO= 8,Gl\P= 242,01= 16 ,RMS= .17 ,ERH= 4.1 ,ERZ= 4.0 >---< :z: c:: 260 2'.1 SEP 1980 12:02:00.3 62.564N 149.164W 2.16 57 we NO= 12 .GAP= 183,01= 15,RMS= .07,ERII= 1 .1 ,ERZ= 1.1 rn CJ 261 24 SEP 1900 12:18:04.8 62.972N 148.928W 1 .42 58 we NO= 6,G71P= 167,01= 32,Rl1S= .12,ERH= 6.0,ERZ== 6.6 262 25 SEP 1900 03:44:52.7 62.489N 148.9941'1 1.98 20 we NO= 15,Gl\P= 200,01= 12,RMS= .29,ERH= 2.7,ERZ= 2.1 263 25 SEP 1980 21:05:29.3 62.903N 149.093W 2.00 10 we NO= 16 ,GAP= 176,01= 15,RMS= . 30 ,ERH= 1 .8,ERZ= 7.4 264 26 SEP 1980 00:41:00.9 63. 278N 148.927W 1 . 62 3 we NO= 9,Gl\P= 263,01= 43 ,RMS= .11 ,ERH"" 3.0,ERZ= 35.0 DEPTH RESTRICTED DUE TO POOR RESOLUTION. 265 26 SEP 1900 02:11:13.2 62.441N 148.680W 1. 28 14 we NO= 14,GAP= 228,01= 4,RMS= .22,ERH= 2.0,ERZ= 2.3 266 27 SEP 1980 20:05:18.0 63.050N 148.950W 1. 07 1 3 we NO= 9,GAP= 272,01= 19,RMS= .39,ERH= 6.2,ERZ= 14.6 267 27 SEP 1980 21:57:24.7 62.733N 148.941W 1 .60 61 we NO= 8,GAP= 196,01= 16,RMS= .04,ERH= 1.1 ,ERZ= 1. 0 268 28 SEP 1980 07:40:21.5 62.460N 148. 707W 1 .06 19 we NO= O,GAP= 283,01= 16 ,RMS= .14,ERH= 2.2,ERZ= 3.1 WOJDWARD-CLYDE CONSULTANTS APPENDIX E -·ESTIMATION OF PRELIMINARY MAXIMUM CREDIBLE EARTHQUAKES E.l -Introduction The approach to estimating the preliminary maximum credible earthquakes (PMCEs) in a region 9 and thereby to establishing a basis for estimating the ground motion at a specific site 9 is based on the premise that significant earthquake activity is associated with faults with recent displacement. The evaluation of the PMCE that may be associated with a given fault is closely related to the tectonic, geologic, and seismologic evaluations of fault activity in the region of the site. Therefore. it is necessary to identify and describe the characteristics and behavior of the faults which have had recent displacement in the region that may be significant to the site even though they may not pass through the site. After the faults significant to a site have been identified, the PMCE for these sources can be estimated. The term preliminary maximum credible earthquake as it is used in this report is Woodward-Clyde Consultants' preliminary estimate, based on limited available data, of the maximum credible earthquake that can occur along a fault with recent displacement. Additional geologic and seismologic studies need to be conducted to refine judgments regarding the size of the maximum credible earthquake that can occur along these faults. Until these additional studies are conducted, the maximum credible earthquakes described in this report are considered preliminary in nature and are so designated. Estimates of the PMCE that can occur along a given fault consider one or more aspects of the relative behavior between faults. Those aspects of behavior--fault parameters--can be compared among faults being evaluated to establish a relative fault ranking with respect to themselves and E - 1 with respect to other faults from around the world. Within the ranking, various faults having similar fault parameters are expected to behave like one another (within rational limits) and, thus~ have similar earthquake potential. Hence, the predictive capabilities of the geologist/seismologist in estimating PMCEs depend largely upon the available data on the fault(s) being evaluated. The principal fault parameters used in evaluating fault behavior in- clude: 1) tectonic setting; 2) geologic-structural setting; 3) style of faulting; 4) physical geometry and mechanical properties of the fault; 5) geologic history of the fault; 6) geologic strain or slip rate; 7) the size, periodicity, and energy of seismic events; B) histor- ical seismicity; 9) fault rupture length; and 10) slip per fault-rupture event. While it would be most desirable to use all of these fault parameters together in an evaluation of maximum magnitude, in actual practice, only a few of the parameters are available for most individual faults. Of these fault parameters, rupture length and slip per event are most fre- quently used by themselves to estimate directly the potential earthquake magnitudes. Empirical relationships have been used relating historical rupture lengths and slip per event to magnitude. By selection of an appropriate rupture length or by use of geologic evidence of slip per event, a corresponding maximum magnitude can be derived from the empiri- cal relations. Such techniques, when used by themselves, can provide results with large errors because they fail to consider the complexities of fault behavior. For example, strike-slip faults in Japan often rupture 100 percent of their length whereas faults in California rupture approximately 30 per- cent of their lengths during the largest earthquakes. Although rupture length is the single most widely used parameter to estimate magnitudes of earthquakes (primarily because fault rupture length appears to be an E - 2 easy parameter to estimate)~ there are no consistent or reliable guide- lines for selection of the appropriate length of rupture that considers fault behavior. The rather arbitrary se 1 ect ion of a rupture 1 ength, such as 50 percent or 100 percent of fault length, without consideration of other fault parameters affecting fault behavior, should be considered preliminary and the magnitude estimates should be used for comparison purposes only. The most rational approach in estimating maximum credible magnitude considers both qualitative and quantitative ( i. e .• empirical} para- meters for ranking faults and characterizing maximum credible earth- quakes. Estimates resulting from the various techniques should be consistent among themselves as well as reasonable according to qualita- tive factors of the evaluation. For this preliminary study, because of the lack of more detailed infor- mation, the PMCE for the crustal faults and lineaments was estimated using fault rupture length. It is recognized that this can result in an unrealistically large earthquake being hypothesized for a given fault. However, the relatively uniform availability of data for this parameter allows an equal basis for comparison of earthquake potential, In addition to the known faults, estimates of PMCEs for the candidate significant features and significant features have been estimated to provide an understanding of the potential impact of these features should they be shown to have recent displacement. Thus, the estimates presented here are not intended as a final assessment of the maximum credible earthquake for these sources but are preliminary in nature, A review of the method is presented below. E.2 -Fault Parameter Method--M itude versus Empirical correlations based primarily on geologic effects resulting from the release of strain (or energy) from an earthquake-generating E -3 volume were initialy proposed by Tsuboi (1956). Tocher (1958) used this concept to formulate relationships of surface-rupture length and dis- placement to magnitude for specific faults in the California-Nevada re- gion. The method was further refined by several workers including Bonilla and Buchanan (1970) who prepared a compilation of the relation- ships of length, magnitude, and displacement. Their formulations and graphs have often been used in estimating maximum credible earthquakes for active fault zones. Slemmons (1977) has updated and revised many of the relationships. Other workers, such as Wyss (1979), have proposed using the area of fault rupture in the subsurface to estimate maximum magnitude. Slemmons' (1977) empirical relationships have been used during this study to estimate maximum credible earthquakes from feature 1 engths. The judgments used to apply Slemmons' relationships to the features are discussed below. It is important, however, to discuss some of the con- straints associated with this method. These constraints include the fact that we know very little about predicting future rupture lengths on faults. We do know that most surface faulting in the western United States ruptures only a small fraction of the total length of the entire fault zone. This fractional rupture-length behavior of faults led to the proposal by Wentworth and others (1969) that future faulting should be assumed to occur along one-half the total fault length. Although this is perhaps reasonable for the western United States, application of this criterion may not be appropriate elsewhere in the world. Another significant problem in using this method is estimating the total length of the fault zone because many faults have complex branching (en echelon or other patterns), and portions of a fault may be concealed. It is clear that judgments of fault length can have significant impact on the half-length criterion for rupture suggested by Wentworth and others ( 196 9) . E - 4 The judgments used to estimate the PMCEs during this study include: a) The obser.ved length of the fault or lineament is assumed to repre- sent the length of fault that could rupture during a single event. In concept, this is different from the half-fault length method of Wentworth (1969), but, when dealing with features of poorly defined length, it is probably a conservative approach. In effect, it is assumed that the observed length of fault is at least half of its total length; thus, many of the length estimates used for the magnitude estimates during this study are probably conservatively long when compared to the half-length method. b) The exception to (a) is the Oenal i fault. The extreme length of this fault, more than 1,250 miles (2,000 km) makes it extremely unlikely that the entire length would rupture during a single event. For the purposes of this preliminary investigation. it is assumed that up to one third of the observed length could rupture during a single event. This fraction of the total fault length is consistent with other worldwide observations of ruptures on long strike-slip faults. It is still a conservative approach, as only the Alaskan earthquake of 1964 and the Chilean earthquake of 1960 are known to have had rupture lengths greater than 415 miles (665 km) and neither of these ruptures occurred along strike-slip faults (Slemmons, 1977). The maximum surf ace rupture 1 ength during the 1906 earth- quake along the San Andreas fault was 270 miles, (432 km) (Streitz and Sherburne, 1980). c) Slemmons' (1977) equations for estimating PMCEs were used. These equations are: Thrust fault Mmax = 4.145 + 0.717 Log L Normal fault Mmax = 1.845 + 1.150 Log L Strike-Slip fault r~max = 0.597 + 1.351 Log L Reverse-Oblique fault Mmax :: 4.398 + 0.568 Log L Worldwide faults Mmax = 1.606 + 1.182 Log L Where Mmax is the maximum credible earthquake and L is the length in meters. E - 5 Where the specific fault type is known, the appropriate equation was used. For lineaments and faults for which the fault type was not known, the equation for worldwide faults was used. These equations are mean values calculated by Slemmons (1977). To provide an independent assessment of the conservatism of these equa- tions, Wyss's (1979) relationship for magnitude versus fault rupture area was used, that is Wyss's method replaced the method of taking plus or minus one standard deviation for Slemmons' (1977) relation- ships. This also permitted an assessment of recent discussions in the scientific community (e. g., Mark, 1977; Mark and Bonilla, 1977, Wyss, 1979, 1980; Bonilla, 1980, among others) about how various methods of calculation of maximum credible earthquakes affect the conservatism involved in estimating maximum credible earth- quakes. d) Wyss (1979; 1980) advocates the use of source area versus magnitude as an empirical relation to estimate magnitudes of future earth- quakes. Theoretically, this method could provide a more accurate means for estimating maximum magnitude because it takes into account both the rupture length at depth and the width of the rupture area. However, the means of obtaining these values and the utility of this method in contrast to the rupture-length method is a topic of con- tinuing discussion (see for instance, Bonilla (1980)). For this study, as discussed above, Wyss's relationship is used as an inde- pendent check on the results obtained using Slemmons' (1977) mean value relationships. The Wyss relationship is: Mmax =Log A+ 4.15 Where A = LW L = half length of the fault W = the down dip length of the fault W< 2/3 L and generally should be 3 to 12 miles (5 to 20 km) E - 6 For comparing results of the two methods, the following assumptions were made in the Wyss relationship: 12 miles (20 km) is used for W where the length is greater than 19 miles (30 km) and W < 2/3 L is used for W where the length is less than 19 miles (30 km). The results compare quite con- sistently for events of magnitude (Ms) greater than approximately 7.0. For magnitudes (Ms) less than 7.0, the Wyss relationship gives a smaller magnitude compared to the results using Slemmons' (1977) relationship. E.3 -Results PMCEs were estimated for the boundary faults using Slemmons' (1977) relationships described above in Section E.2. In addition, a pre- 1 iminary maximum credible earthquake of magnitude (Ms) 8.5 has been assigned to the Benioff zone using the 1964 magnitude (Ms) 8.4 event as a basis. A summary of these results is presented in Section 11. E - 7 APPENDIX F -QUALITY ASSURANCE Woodward-Clyde Consultants maintains a company-wide program of quality assurance pertaining to all aspects of its professional~ technical, and support services. The objective of the program is to maintain the quality of company activities including the implementation and comple- tion of a large project such as the seismic studies being conducted for the Susitna Hydroelectric Project. For the purposes of this program, quality assurance is defined as: A management program of planned and systematic actions, having the objec- tive of providing adequate confidence that services are performed in accordance with standards of professional practice and the require- ments of the Client (Acres American Inc.). The essential components of the quality assurance program are: to establish lines of responsibility, authority, and accountability; to provide a qualified staff; to define the method of operation and to provide documentation of activities; to establish internal review (peer review) procedures; and to provide procedures for auditing. F.l -Responsibility, Authority, and Accountability Dr. Ulrich Luscher is the Principal-in-Charge of the seismic studies conducted for the Susitna Hydroelectric Project. He is responsible for all aspects of the project. George Brogan is the Project Manager who is responsible to the Principal-in-Charge for completion of the scope of services defined in the contract between Acres American Inc. and Woodward-Clyde Consultants. F - 1 Professional and technical staff have performed the services required by the Project under .the direction of the Project Manager. Outside con- sultants have also worked under the direction of the Project Manager as part of the professional staff. F.2 -Methods of Operation The methods of ope rat ion have been estab 1 i shed to meet the scope of services in a timely, cost-effective, repeatable manner. They are intended to provide a product that meets the level of quality commen- surate with standards of professional practice, the Project, and Acres American Inc. The components of the method are summarized below. Work Plan The initial effort on the Project was to prepare a work plan. The plan was based on the Task 4 contractual agreement and describes subtask objectives, task descriptions, time schedules, and budgets. T h e w o r k p 1 an i d e n t i f i e's t h e p 1 a n f o r s t a f f i n g of t h e p r o j e c t , including the Principal-in-Charge, the Project Manager, and key professional staff members. In addition, the work plan identifies the review staff, project consultants, subcontractors, other firms with whom services must be coordinated, and areas of potential difficulties and/or delays. The completed work plan was approved by the Project Manager and served as the basic guide for providing services on the Project. Woodward-Clyde Consultants assigned an identification number (14658A) to the Project. A master file is located in the Orange, California, office of Woodward-Clyde Consultants. Upon completion of the project, the file will be kept, abstracted, or disposed of according to the F - 2 policies established by Acres American Inc. and/or by the Regional Managing Principal of ~Joodward-Clyde Consultants. All significant information, including the location and content of secondary project files (such as specialized discipline files) are contained in the master file. Data Acquisition Data were acquired as outlined in the work plan. Data acquisition was accomplished using methods described in Section 2.5 and in Appendices A and B. Data were acquired with the objective of obtaining results that are objective, true, repeatable, and of known accuracy. Data Anal is All data analyses and interpretations are based on logical, systematic procedures. Where it has been appropriate to the project, background considerations and technical concepts utilized in each analysis have been recorded as the analysis was performed, in order that the analytical process could be reconstructed by a knowledgeable reviewer. Only certified or cross-checked computer programs have been used in connection with project c.alculations and analyses. Certification of project computer programs, such as the Woodward-Clyde Consultants' Earthquake Data Bank, has been conducted in the past and accepted for previous major projects for federal agencies and/or utility clients. Development of opinions, recommendations, and conclusions has been the major purpose of the project activities. All opinions, criteria, designs, specifications, drawings, recommendations, and conclusions which have been developed are the professional responsibility of the Project Manager. The Project Manager has reviewed the profess ion a 1 s under his responsibility to verify that they have the required capabilities to analyze data and to develop opinions, recommenda- tions, and conclusions commensurate with the needs of the Susitna Hydroelectric Project Task 4 scope of services. F - 3 Statement of Opinions~ Recommendations~ and Conclusions At appropriate stages~ indicated results~ conclusions, and recommen- dations have been discussed with Acres American Inc. Formal discus- sions have were held on 10 June 1980 prior to initiation of the field studies~ on 21 through 23 August 1980 at the conclusion of the field program, and on 22 through 24 October 1980 midway through the data analysis portion of the investigation. This report constitutes the formal presentation of opinions, recom- mendations, and conclusions for the 1980 work plan. A similar report will be prepared at the conclusion of the 1981 work plan after project feasibility has been evaluated. Opinions, recommendations, and conclusions occasionally have been pro- vided orally. Where appropriate, these opinions, recommendations, and conclusions have been documented in the project file. Peer Review Review is an integral part of all professional services rendered by Woodward-Clyde Consultants. It consists of requiring that one or more peers review opinions, recommendations, and conclusions to determine their adequacy on the basis of the data which have been acquired and the analysis which has been done. The Project Manager is responsible for the selection of peer reviewers, for assuring that the peer review is made and documented, for verifying that the peer reviewer has the necessary knowledge and skill to perform the review adequately (and is not directly involved in the activity reviewed), and for seeing that the results of the peer review are incorporated in the study. For this project, peer review was supplemented by a formal review board composed of experts in the field of seismic geology. These experts include members of Woodward-Clyde Consultants and an outside con- sultant described below in Section F.4. F - 4 F.3 -Documentation of Activities Activities including data acquisition and analysis, which are key parts of the study and which lead to the opinions, interpretations, and conclusions upon which this report is based, have been documented in accordance with procedures described in Sections 2.5 and 12 and in Appendices A and B of this report. Documentation is summarized as appropriate in this report. Additional documentation of activities which are important to providing repeatability of results, accurate results, and results that can be adequately reviewed by an independent review are filed in the project master file in the Orange~ California, office of Woodward-Clyde Consultants. Supervision of adequate docu- mentation procedures has been the responsibility of the Project Manager. This responsibility has been delegated to key professional members of the project team when appropriate. F.4 -Internal Review Procedures As summarized in Section F.2. internal review procedures for this pro- ject have included review by the project peer reviewers and by an internal review board (designated the Internal Review Panel). Project peer reviewers were members of the Internal Review Panel and were not involved with the technical production of the portion of the study for which they were providing peer review. The Internal Review Panel consisted of the peer reviewers, senior members of the Susitna Hydroelectric Project team experienced in seismic studies and Alaska geologic and seismologic conditions 9 and an outside consultant--Bob Forbes, Professor Emeritus of Geology 9 University of Alaska at Fairbanks. Table F-1 lists the peer reviewers, the Internal Review Panel members, and their respective review responsibilities. The peer reviewers possess the technical qualifications, practical exper- ience. and professional judgment, in the opinion of the Project Manager F - 5 and the Principal-in-Charge, to conduct the review of the project. The discuss ion be 1 ow presents the deta i 1 s of the review process and the documentation of the results. The review process included a critical evaluation of the basis and validity of all significant conclusions, opinions, evaluations, recom- mendations, designs, and other material required as an end result of the project services. The review (including peer review) did not include a complete check of detailed calculations, but emphasized establishing the validity of the technical approach and other procedures used to form an opinion of the suitability of the end result. Specific items considered in the review were: -Verification of scope and objectives -Validity of the technical approach -Validity of data used in analysis of evaluations -Thoroughness and completeness of the services -Validity and suitability of end results -Clarity of presentation, including sketches, drawings, and reports -Clarity of statement of limitation -Fullfilment of agreement between Woodward-Clyde Consultants and the Client (Acres American Inc.) As a final step in their review, the reviewers (including peer re- viewers) discussed their findings with the originators and resolved or defined any items of disagreement. When differences remained between originator and reviewers, they were resolved under the direction of the Project Manager or the Principal-in-Charge prior to completion of the review process. F - 6 The review process involved the following: (a) A review was conducted by one peer review member and two members of the Internal Review Panel of the status of the investigation immediately prior to the geologic field reconnaissance study. This review included evaluation of the planned field reconnaissance study. The review was conducted on 27 June 1980. Results of the review were incorporated into the field study. document the results of the review. I nforma 1 notes (b) A peer review was conducted midway through the geologic field reconnaissance study. This review was conducted by a peer reviewer from 29 through 31 July 1980. A memorandum summarizing the results of the review are on file in the master project file. (c) A review of the geologic field reconnaissance study was conducted by peer reviewers and by the Internal Review Panel members in the field at the conclusion of the field study. The review was conducted from 22 through 24 August 1980. A memorandum summarizing the results of the review are on file in the master project file. (d) A review of the short-term seismologic monitoring program was conducted by a member of the Internal Review Panel during operation of the network. The review was conducted from 2 through 24 August 1980. Rev i evi comments were incorporated into the network opera- tions. (e) A review of the draft report was made by peer reviewers and by the members of the Internal Review Panel. This review was conducted between 1 and 5 December 1980. Written comments on the reports were incorporated into the final report issued to Acres American Inc. Peer review statements (Figure F-1) were completed by the appro- priate peer reviewer and filed in the master project file. F - 7 F .5 -Audits The Quality Assurance Officer in the Orange, California, office of Woodward-Clyde Consultants monitors proper conduct of peer review pro- cedures for projects such as Task 4 of the Susitna Hydroelectric project. In addition, the Quality Assurance Officer of the Western Region of Woodward-Clyde Consultants periodically holds quality assur- ance audits to verify the pr~per conduct of the peer review procedures. Procedures for audits are covered in the Woodward-Clyde Consultants Quality Assurance Manual. F - 8 TABLE F -1 ECT PEER REVIEW AND INTERNAL REVIEW PANEL MEMBERS Subtask Review Responsibility Review Member Affiliation Peer Internal Review Panel Or. Duane Packer Woodward-Clyde 4.01, 4.03, 4.01 through 4.06 Consultants 4.05, 4.06 Dr. Tom Turcotte Woodward-Clyde 4.02, 4.06 None Consult ants U. Savage Woodward-Clyde 4.04 4.02, 4.04, 4.06 Consultants George Brogan Woodward-Clyde None 4.01 through 4.06 Consultants Dr. Robert Forbes University of None 4.05, 4.06 Alaska, Fairbanks Or. I. M. Idriss Woodward -C 1 yde 4.07, 4.08 None Consu 1 t ants Subtask descriptions are: 4.01-Review of available data 4.02 -Short-term seismologic monitoring 4.03-Preliminary evaluation of reservoir-induced seismicity 4.04 -Remote sensing analysis 4.05 -Seismic geology reconnaissance 4.06 -Evaluation and reporting 4.07 -Preliminary ground motion studies 4.08 -Preliminary analysis of dam stability PEER REVIE~ DOCUMENTATION --------------------------------------------No. _________ _ Specified Scope of Review ____________________________ _ REVIEWER'S STATEMENTS A. 1 have reviewed the above-referenced project in accordance with the speci- fied scope. My conclusions are ~s follows: 1. Conformation to required scope and definition of service 2. Basic field and laboratory data 3. References, documents, and correspondence in files 4. Assumptions, technical approaches, .lind solutions 5. Checking of calculations, drawings, graphs, and tables 6. Specifications, opinions, judg- ments, conclusions, ~nd recommendations 7. Organization, clarity, and completeness of report 8. Others _________ _ Satis-See Comment Not factory Number Applicable Ccmments: ____________________________________________ __ Attached are additional comments Nos. ________________ _ Reviewer ____________ Date ________ _ B. I have discussed my corrments with the originator, _________ _ and all have been resolved as described in ~ttachments _________ ___ exc2pt Nos. __________________________________ __ Rev1 ewer _____________ Date. ______ _ Comments not resolved by reviewer discussions with originator have been resolved as described in Responsible Pri ·------------Date'-------- Rev. No. 0 Date 20 Dec 1977 I~R Peer Review Procedure Page 5 WOODWARD·CL YDE CONSULTANTS 14658A December 1980 FIGURE F-1 APPENDIX G -GLOSSARY Allochthonous Aleutian Megathrust Amygdaloidal Anastomosing Stream Anelasticity Aseismic Batho 1 ith Formed or occurring elsewhere than in place; of foreign origin or introduced. The major collision boundary between the Pacific and North American Plates where the Pacific Plate is descending into the earth's mantle. Gas cavities in igneous rocks that have been filled with secondary minerals such as quartz, calcite, chalcedony, or zeolite. A stream that divides into or follows a complex network of several small, branching and reuniting shallow channels separated from each other by islands or bars, resembling in plan the strands of a complex braid. The effect of attenuation of a seismic wave; it is symbolized by Q. An area of generally low seismicity that can have tectonic deformation which is not accompanied by earthquakes. A large, generally discordant mass of igneous rock which was intruded originally at depth and now has more than 40 square mi 1 es (104 km2) in surface exposure. It is composed predominantly of medium to coarse grained rocks, often of granodiorite com- position. G - 1 Benioff zone Candidate Feature Candidate Significant Feature Cat ac 1 as tic Consanguineous Crag and Tail Seismicity associated with plates of the earth's crust which are sinking into the ·upper mantle. In Alaska, the Benioff zone is associated with underthrusting of the Pacific plate beneath the North American plate. A term used in this study to identify faults and lineaments that may affect Project design cons ide rat ions based on the application of length-distance screening criteria prior to field reconnaissance studies. A term used in this study to identify faults and lineaments that may affect Project design considerations based on length-distance screening criteria and a preliminary assess- ment of seismic source potential and poten- tial surface rupture through either site using the results of the field reconnaissance studies. The granular fragmental texture induced in rocks by mechanical crushing. The relationship that exists between igneous rocks that are presumably derived from the same parent magma. An elongate hill or ridge resulting from glaciation. The crag is a steep face or knob of ice-smoothed, resistant bedrock at the end of the ridge from which glacial ice came. The tail is a tapering, streamlined, gentle G - 2 Dextral Fault Drift Drumlin Ductile Dynamometamorphism End Moraine Fault Fault with Recent Displacement slope of intact weaker rock and/or till that was protected in part from the glacial ice by the crag. A strike-slip fault along which, in plan view, the side opposite the observer appears to have moved to the right. All rock material transported by a glacier and deposited directly by or from the ice or by meltwater from the glacier. An elongate or oval hill of glacial drift. A rock that is able to sustain, under a given set of conditions, 5 to 10 percent deforma- tion before fracturing or faulting. The alteration of rock characteristics primarily by mechanical energy (pressure and movement). A ridge of glacial sediments deposited at the margins of an actively flowing glacier. A surface or zone of closely spaced fractures along which materials on one side have been displaced with respect to those on the other side. As defined for this study, a fault which has had displacement within approximately the last 100,000 years. G - 3 Flysch Geosyncline Glacial Scour Gouge Hypocenter Intercalated Kame A thick and extensive deposit largely of sandstone that is formed in a marine environ- ment (geosyncline) adjacent to a rising mountain belt. A mobile downwarping of the crust of the earth, either elongate or basin-like, that is subsiding as sedimentary and volcanic rocks accumulate to thicknesses of thousands of meters. GeosynGlines are usually measured in scores of kilometers. The eroding action of a glacier, including the removal of surficial material and the abrasion, scratching, and polishing of the bedrock surface by rock fragments dragged along by the glacier. Soft clayey material often present between a vein and a wall or along a fault. That point within the earth that is the center of an earthquake and the origin of its elastic waves. A material that exists as a layer or layers between layers or beds of other rock; interstratified. A short ridge, hill, or mound of poorly stratified sediments deposited by glacial meltwater. G - 4 Kettle Klippe Lee Lineament L it-par-1 it Magnitude Consultants A steep-sided, usually basin-or bowl-shaped hole or depression without surface drainage in glacial deposits. An outlying isolated remnant of an overthrust rock mass. T he s i d e of a h il l , k n o b , o r prom i n en t roc k facing away from the direction from which an advancing gl~cier or ice sheet moved; facing the downstream side of a glacier. A linear trend with implied structural control (including but not limited to fractures, faults, etc.) typically identified on remotely sensed data. Having the characteristic of a layered rock, the layers of which have been penetrated by numerous thin, roughly parallel sheets of igneous material. Magnitude is used to measure the size of instrumentally recorded earthquakes. Several magnitude seal es are in common usage (Richter, 1958). The differences in these magnitudes are caused by the way in which they are each calculated, specifically, the periods (frequency) of the waves which are used in each measurement. ML is the original Richter magnitude which was devel- oped for Southern California earthquakes recorded on Wood-Anderson seismometers (free G - 5 Metabasalt Microearthquake Migmatite Miogeosyncline Modified Mercalli Scale Noncomformity period 0.8 second) at distances of 372 miles (600 km) or less. Ms and Mb use signals recorded at teleseismic distances 1,240 miles (2,000 km or greater). Ms measures the amplitude of surface waves with periods of 20 seconds and the Mb is a measure of the 1 second body waves. The variations in the magnitude calculations are due in part to the fact that different size earthquakes generate relatively different amounts of energy in these frequency bands. Volcanic rock (basalt) altered by temperature and pressure to a metamorphic rock. An earthquake having a magnitude (ML) of three or less on the Richter scale; it is generally not felt. A rock (gneiss) produced by the injection of igneous material between the laminae of a schistose formation. A geosyncline in which volcanism is not associated with sedimentation. An earthquake intensity scale, having twelve divisions ranging from I (not felt by people) to XI I (damage nearly total). A substantial hiatus in the geologic record that typically implies uplift and eros ion. The gap occurs between older igneous or metamorphic rocks and younger sedimentary rocks. G - 6 Normal Fault Pluton Pyroclastic Rejuvenation Reservoir-Induced Seismicity Reverse Fault Significant Feature A fault along which the upper (hanging) wall has moved down relative to the lower wall (footwall). An igneous intrusion formed at great depth. Formed by fragmentation as a result of a volcanic explosion or aerial expulsion from a volcanic vent. Renewed downcutting by a stream caused by regional uplift or a drop in sea level. The phenomenon of earth movement and resul- tant seismicity that has a temporal an.d spatial relationship to a reservoir and is triggered by nontectonic stress. A fault in which the upper (hanging) wall appears to have moved up relative to the lower wall (footwall). A term used in this study to identify the faults and lineaments that are considered to have a potential effect on Project design considerations pending additional studies. Selection of these features was made on the basis of length-distance screening criteria and final assessment of their seismic source potential and potential for surface rupture through either site using the results of the field reconnaissance studies. G - 7 Slickensides Solifluction Stade Stoss Stoss and Lee Topography Stratovolcano A polished and smoothly striated surface that results from friction during movement along a fault plane. The slow (0.2 to 2 inches/yr (0.5 to 5 cm/yr)) creeping of wet soil and other saturated fragmental material down a slope, especially the flow initiated by frost act ion and augmented by meltwater from· alternate freezing and thawing of snow and ground ice. A substage of a glacial stage; time repre- sented by glacial deposits. The side or slope of a hill, knob, or prominent rock facing the direction from which an advancing glacier or ice sheet moved; facing the upstream side of a glacier. An arrangement, in a strongly glaciated area, of s m a 11 h i 1 1 s or prom i n en t rocks h a v i n g gentle slopes on the stoss side, and somewhat steeper, plucked slopes on the lee side. A volcano composed of explosively erupted cinders and ash interbedded with occasional lava flows. G - 8 Talkeetna Terrain Thrust fault Whal eback Region (including the Project) of relatively uniform response within the current stress regime. The Terrain has the follo111ing boundaries: the Oenal i-Totschunda fault on the north and east, the Castle Mountain fault on the south, a broad zone of deformation and volcanoes on the west and the Benioff zone at depth. The Terrain is inferred to be a relatively stable tectonic unit with major strain release occurring along its boundaries. A low angle reverse fault. A small, elongate, protruding knob or hillock of bedrock, most commonly granitic, sculp- tured by a large glacier so that its long ax i s i s or i e n ted i n t h e d i r e c t i on of i c e movement. It is characterized by an upstream side that is gently inclined and smoothly rounded but striated and by a downstream side that is steep and rough. G - 9 APPENDIX Acres American Inc., 1980, Design transmittal-nitial version--Prelimi- nary licensing documentation: Alaska Power Authority, Anchorage, Alaska Task, 10.2. 60 p., 3 appendices. Adams, R. D., Gough, D. I., and Muirhead, K. J., 1973, Seismic surveil- lance and artificial reservoirs: UNESCO Working Group on Seismic Phenomena Associated with Large Reservoirs, Annexure 1. Third Meeti , London, England, Report, 8 p. Agnew, J. D .• 1980, Seismicity of the Central Alaska Range, Alaska, 1904 978: ster s Thesis, University of Alaska, Fairbanks, Alaska, 95 p. Albee, A. L. fault act ed s .• E Engineer ith. J. L .• 1966, Earthquake aracteristics and ity in southern i ia, in Lung. R .• and Proctor, R. ineeri geology in southernCalifornia: Associated log sts, Glendale. i ia. p. 9-33. Anderson, J. G., • Est ing ture for seismic-risk studies: seismici from geological struc- Bullet n of the Seismological 58. Society of Jl.mer a, v. s p, Andreason, G. E., Grantz, A .• Zietz. I., and Barnes. D. F., 1964, Geol ic i at gravity data in the Copper River si Paper -H • Ambrasseys, N. N .• 1 • 0 • Biaz, ran, earthquake N , v. • p. 903-904. Augu 1968: , Latera mantle above variations seismic-Baraz i. M.. and I sac wave attenuation zone of the Journal a Is 1 • deep i ined earthquake the upper mantle: ical Research, v. Barnes. F. F,. and P • T. G .• Hill District, Survey Bulletin a 1016. 85 p, 1 Field, a: Beikman~ H. east Fi d 1978. Bell, M, L., ad Nut~, i pressure ogical ,000' 1 ic map of r~ i south- laneous ic m of Alaska: U. S. Geological sheets. 1978, Strength changes due to reservoir stresses applications to Lake Oroville: • p. -4483. H 1 Bhattacharya, B., and Biswas, N. N., 1979, Implications of North Pacific tectonics in central Alaska: Focal mechanism of earthquakes: Tectonophysics, v. 19, p. 361-367. Bishop, E. E., Eckel, E. B., and Others, 1978, Suggestions to authors of the U.S. Geological Survey (6th ed.): Washington, D.C., U. S. Government Printing Office, 273 p. Biswas. N. N., 1973, P-wave travel time anomalies, Aleutian Alaska region: Tectonophysics, v. 19, p. 361-367. Biswas, N. N., 1980, University of Alaska Geophysical Institute, Fairbanks, Alaska, Personal Communication. Biswas, N. N., and Bhattacharya, B., 1974, Travel-time relations for the upper mantle P-wave phases from central Alaskan data: Bulletin of the Seismological Society of America, v. 64, p. 1953-1965. Bonilla, M. G., 1970, Surface faulting and related effects in earthquake engineering, in Wiegel, R. L., ed., Earthquake engineering: Engle- wood Cliffs, New Jersey, Prentice Hall, p. 47-74. 1979, Historic surface faulting--map patterns, relation to sub- surface faulting, and relation to preexisting. faults, in Evernden, J. F., convener, Proceedings of Conference VIII--Analys1S of actual fault zones in bedrock: U. S. Geological Survey Open-File Report 79-1239, p. 36-65. 1980, Comment and reply on 11 Estimating maximum expectable magni- tudes of earthquakes from fault dimensions 0 : Geology, v. 8, p. 162-163. Bonilla, M. G., and Buchanan, J. M., 1970, Interim report on worldwide historic surface faulting: U. S. Geological Survey Open-File Report, 31 p. Boucher, G. C., and Fitch, T. J., 1969, Microearthquake seismicity of the Denali fault: Journal of Geophysical Research, v. 74, p. 6638-6648. Bruhn, R. L., 1979, Holocene displacement measured by trenching the Castle Mountain fault near Houston, Alaska: Alaska Division of Geological and Geophysical Surveys, Geology Department 61, p. 1-4. Cady, W. M., Wallace, R. E, Hoare, T. M., and Webber, E. J., 1955, The central Kuskakwim region, Alaska: U. S. Geological Survey Profes- sional Paper 268, 132 p. California Division of Mines and Geology, 1976, Active fault mapping and evaluation program: Ten year program to implement Alquist-Priolo special studies zones act: Special Publication 47, 42 p. Carder, D. S., 1945, Seismic investigations of the Boulder Dam area, 1940-1944, and the influence of reservoir loading on earthquake activity: Bulletin of the Seismological Society of America, v. 35, p. 175-192. H - 2 1970, Reservoir loading and local earthquakes, J!l Adams, W. M., ed., Engineering geology case histories number 8: Engineering seismo1ogy: The works of man: Boulder, Colorado, Geological Society of America, p. 51-61. Chase, C. G., 1980, University of Minnesota. Minneapolis, Personal Commun ica.t ion. Cluff, L. S., Packer, D. R .• and Moorhouse. D. C .• 1977, Earthquake evaluation studies of the Auburn Dam area--Volume 1--Summary re- port: U. S. Bureau of Reclamation. Denver, Col or ado, Contract 6/07/DS/72090, 87 p. Cluff, L. S., Tocher·. D .• and Patwardhan, A. S., 1977, Approach to probability evaluation of design earthquakes for nuclear power plants: World Conference on Earthquake Engineering, Sixth. New Delhi~ India, Proceedings, v. 3~ p, 2587-2593. Cormier, V .• 1975, Tectonics near the junction of the Aleutian and Kuril-Kamchatka areas. and a mechanism for middle Tertiary mag- matism in the Kamchatka Basin: Geological Society of America Bulletin, v. 86~ p. 443-453. Crouse, C. B •• and Turner. B. E.. 1980~ Processing and analysis of Japanese accelerograms and comparisons with U. S. strong motion data: World Conference on Earthquake Engineering, Seventh. Istan- bul, Turkey~ v. 2, p. 419-426. Csejtey, B •• Jr., • Reconnaissance geologic investigations in the Talkeetna Mountains, Alaska: U. S. Geological Survey Open ile Report 74-147. 48 p. 1976, Tectonic impl ations of a late Paleozoic volcanic arc in the Talkeetna Mountains, south-central Alaska: Geology~ v. 4. p. 49 2. ----1980, U. S. Geological Survey, Menlo Park, California, Personal Communication. Csejtey, B., Jr .• Nelson, W. H., Jones~ D. L., Silberling~ N.J., Dean, R. M., Morris, M. S, Lanphere. M. A .• Smith, J. G .• and Silbermen, M. L., 1978, Reconnaissance geologic map and geochronology, Talkeetna Mountain Quadrangles northern part of Anchorage Quad- rangle. and southwest corner of Healy Quadrangle. Alaska: U. S. Geological Survey Open-File Report 78-558-A. 62 p. Csejtey, B.~ and iscom, A.~ 1978, Preliminary aeromagnet inter- pretative map of t Talkeetna Mountains quadran 1e? Alaska: U.S. Geological Survey Open File Report 78-558 , sc e 1:250,000, 14 p., 2 ates. Dames and Moore, 1975, Subsurface geophysical exploration--proposed Watana Damsi on the Susitna River: U. S. Army Corps of Engi- neers, Alaska District, unpublished report, 12 p .• 2 appendices. H - 3 Davies, J. N., 1975, Seismological investigations and plate tectonics in southcentral Alaska: Ph.D. dissertation, University of Alaska, Fairbanks, Alaska, 192 p. 1978, Report summary; Operation of a seismic data collection and analysis center in Alaska, in Seiders, W., and Thomson, J., compilers, Nat i anal Earthquake Hazards Reduct ion Program--Summaries of technical reports, Volume 7: U. S. Geological Survey, Menlo Park, California, p. 393-394. Davies, J. N., and Berg, E., 1973, Crustal morphology and plate tecton- ics in south-central Alaska: Bulletin of the Seismological Society of America, v. 63, p. 673-677. Davies, J. N., and House, L., 1979, Aleutian subduction zone seismicity, volcano-trench separation, and their relation to the great thrust- type earthquakes: Journal of Geophysical Research, v. 84, p. 4583-4591. Davis, T. N., 1964, Seismic history of Alaska and the Aleutian Islands: Bibliographical Bulletin of American Geophysics and Oceanography, v. 3, p. 1-16. Davis, T. N., and Echols, C., 1962, A table of Alaskan earthquakes 1788-1961: University of Alaska, Geophysical Institute Research Report No. 8, 2 p. Detterman, R. L., Plafker, G., Hudson, T., Tysdal, R. G., and Pavoni, N., 1974, Surface geology and Holocene breaks along the Susitna segment of the Castle Mountain fault, Alaska: U. S. Geological Survey Miscellaneous Field Studies Map MF-618, scale 1:24,000, 1 sheet. Detterman, R. L., Plafker, G., Tysdal, R. G., and Hudson, T., 1976, Geology of surface features along part of the Talkeetna segment of the Castle Mountain-Caribou fault system, Alaska: U. S. Geological Survey Miscellaneous Field Studies Map MF-738, scale 1:63,360, 1 sheet. Dewey, J. F., 1972, Plate tectonics, in Wilson, J. T., compiler, Continents adrift and continents aground: San Francisco, Freeman and Company, p. 34-45. Dobry, R., Idriss, I. 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