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Susitna-Watana Hydroelectric Project Deterministic Ground Motion for Slab Events Review Copy AEA11-022 March 10, 2014
SUSITNA-WATANA HYDRO Clean,reliable energy for the next 100 years. Technical Memorandum 14-04-TM v1.0 Susitna-Watana Hydroelectric Project Deterministic Ground Motion for Slab Events (Acknowledgement to the major contributions by Norm Abrahamson) Review Copy AEA11-022 Prepared for: Alaska Energy Authority MWH 813 West Northern Lights Blvd.1835 South Bragaw St.,Suite 350 Anchorage,AK 99503 Anchorage,AK 99508 THIS DOCUMENT IS CONSIDERED CEll CRITICAL ENERGY INFRASTRUCTURE INFORMATION DO NOT RELEASE March 10,2014 =ALASKA 13-1404-TM-031014tm) MK)ENERGY AUTHORITY THIS PAGE INTENTIONALLY LEFT BLANK The following individuals have been directly responsible for the preparation,review and approval of this Report. Dina Hunt.Senior Geotechnical EngineerPreparedby: Reviewed by:Norm Abrahamson,Engineering Seismologist Approved by: Michael Bruen,Geology,Geotechnical,Seismic Lead Approved by: Brian Sadden,Project Manager Disclaimer This document was preparedfor the exclusive use ofAEA and MWH as part of the engineering studies for the Susitna-Watana Hydroelectric Project,FERC Project No.14241,and contains information from MWH which may be confidential or proprietary.Any unauthorized use of the information contained herein is strictly prohibited and MWH shall not be liable for any use outside the intended and approved purpose. THIS PAGE INTENTIONALLY LEFT BLANK 2 ALASKA ENERGY AUTHORITY SUSITNA-WATANA HYDRO AEA11-022 , 13-1404-TM-031014 Clean,reliable energy for the next 100 years.CEll TABLE OF CONTENTS 1.SYNOPSIS 1 2.INTRODUCTION 3 2.1 PUILPOSE ......ssccscsescssencessevecessessseseceescsssossosssssesssssessceeceossscssesenseseesensssesesessssenssensenssessoseseeesaes 4 2.2 --PrOCECUI€........sesesessssesecsvssescscetssesessssccasscesssasssesessecesceasvesacesescessceaseaescessenssceasseseseesseessasensegs 4 3.RUPTURE GEOMETRIES FOR LARGE SLAB EARTHQUAKES 6 4,DETERMINISTIC GROUND MOTION FOR SLAB EVENTS 10 5.CONCLUSION 22 6.REFERENCES 26 List of Tables Table 1.Slab Events with Finite Source Inversions from Literature ReView.........cccsssssssssscssssssescescencencesceneenes 7 Table 2.Summary of Finite Fault Solutions for the Selected Intraslab Earthquakes ............ccccscsscescereeeeenes 8 Table 3.Slab Plane Parameter .............esescescesseeescescescescecesaccecsceseeseeseeeesceeceseessesesscesseececescessenseasenseaasacees 10 Table 4.Closest Approach Distances of Intraslab Seismic Source..............ssssscesessesseeeseeeeseeteceeceeeseeneecens 10 Table 5.Rupture Geometry for M7.8 and M8.0 ue sesesscssctscrecsececcsecsecsssesecsesscescsssssssscessessesssseesseenss 15 Table 6.Hypocentral Depths and Distances for M7.8 &M8.0 Events ..eccccssssccsssescssssssssssssssssessssseessnsees 18 Table 7.Comparison of Deterministic Ground Motion Computed using Different Approaches...............21 List of Figures Figure 1.Example of Rupture Geometries of Slab earthquakes,both Narrow and Wide Ruptures are shown.Based on AEIC dip angle of 25 degrees and WSN 2 sigma width of 12.3km (Fugro,2013).........4 Figure 2.Illustration of 2:1 and 1:2 Aspect Ratios (length:width).........sscsssessssssesssececeenenesstseesssesseneeseees 6 Figure 3.Slab Planes,three dimensional figure shown on the left for McKinley Block (planes 1-4)and plan view of all planes shown on the right.(FUgro,2013).....sscessssssssssssenesessseseseseenenstsesestsasatseceseseenseneness 11 Figure 4.Recorded seismicity from locally installed seismometers that show Intraslab plane in profile. (Fugro,2013).Vertical and horizontal standard location errors SHOWN........---ssssceeseeeeereressereseseeeensseaeenenes 12 Figure 5.AEI Seismicity and Location of Slab Planes,grid with correlation distance of 15km (Fugro, 2013).cssscsssssescsssssecscecsesescsesesesecscucscsssssssesosososesssssssssssssssesesseateasesensseresssssssssncsasensnssesesecesnanansnssescaoeoseenseesesey 13 Figure 6.Magnitude-Area Scaling Relationship Comparison ............ssssssscssssesssesneseesessessenssesnessanseceseesesees 14 REVIEW COPY Page i 03/10/14 Zz ALASKA ENERGY AUTHORITY AEA11-022SUSITNA-WATANA HYDRO saetana 022 Clean,reliable energy for the next 100 years.CEll Figure 7.Locations of Hypocenters on the Rupture Plane for an M8 Slab Earthquake.............cscs 15 Figure 8.Locations of Hypocenters on the Rupture Plane for an M7.8 Slab Earthquake.........ccsssesseseees 16 Figure 9.Possible Slab Ruptures for a Magnitude 8 event,red star illustrates the hypocenter with the closest distance.(Blue diamonds represent uniformly distributed hypocenters (see Figure 7)for a M8.0 Carthquake)......scececeescsessesssscesssssseessscecsssessssssssesssscsssssssssssssssssessssessessssseseesessssesessseeeseneessasenesseneesenesneaneneaes 17 Figure 10.California DSOD Consequence-Hazard Matrix ..........ccsssscsssssessssssesesseeeeeseseeeeeseerssesesesasnesnenes 23 Figure 11.Comparison to Draft Probabilistic Seismic Hazard Analysis (Fugro,2012)......ssssssssseereenees 24 Figure 12.Comparison to Draft Intraslab Sensitivity Analysis (FUgro,2013).....scsesessssessessseseseseseseseeees 25 LIST OF APPENDICES Appendix A:Finite Fault Solutions Figure A 1.2001 Geiyo Earthquake (Asano et al.,2004).......csssssssssssssscsssssssersseessssensenesseseseenssneseeseateneneens 2 Figure A 2.2001 Geiyo Earthquake (Sekiguchi and Iwata,2002)(From Mai Database)..........sssssseeeseees 2 Figure A 3.2001 Geiyo Earthquake (Kakehi,2004)(from Mai Database).........cssessssesesessseessstseeseeeseens 3 Figure A 4.2003 Off-Miyage Earthquake (Asano et al,2004)...sssssecsscrssssessssssorcsscssssssssessecesseseceeseses 3 Figure A 5.2008 North Iwate Earthquake (from Sazuki et al,2009)..........cssesssssssssssscsssscssescnsenceeeasseeessnees 4 Figure A 6.1949 Olympia Earthquake (Ichinose et al,2006)..........scesssssssessseesscesscssesstecesseneses aesceaceeeeoeees 4 Figure A 7.1997 Michoacan Earthquake (Santoyo et al,2005)......sessssssssssesssscssesssssssssesssssssessssceseeeasenees 5 Figure A 8.1999 Oaxaca Earthquake (Hernandez et al,2001)...cecssssscessessescceeessesseeeserecsessescesseeseesnees 5 Figure A 9.1999 Oaxaca Earthquake (Hernandez et al,2001)(from Mai database)...........ceesseseeseeeeseeeees 6 Figure A 10.2001 El Salvador Earthquake (Vallee et al.,2003)..........cscsessscsseceeesecceeseneesseeesccceseeeescaceetneees 6 Figure A 11.2001 Nisqually and 1965 Seattle-Tacoma Earthquake (Ichinose et al.2004)...eeeseeteeeees 7 Appendix B:Slab Geometries Figure B 1.2001 Geiyo Earthquake Earthquakes in the Philippine Sea Slab (Xu and Kono,2002)...........2 Figure B 2.2001 Geiyo Earthquake Philippine Sea Slab earthquakes with the approximate location of the 2001 Geiyo earthquake (modified from Nakajima and Hasegawa,2007).......scsssssssssssssesssessssescesssssssesssees 3 Figure B 3.2003 Off-Miyagi Earthquake Structure of the Pacific Slab from velocity and earthquakes (aftershocks and background seismicity)in the Pacific Slab (Mishra and Dapeng,2004)..........cssssesssseees 4 Figure B 4.2003 Off-Miyagi Earthquake Mainshock and aftershocks with respect to the upper Pacific Plate boundary (Okada and Hasegawa,2003)........cssssssssssssssssessssessssesscsssscsscssssssssassssscsesessssacseceseceasscsacecsess 5 REVIEW COPY Page ii 03/10/14 Zz ALASKA ENERGY AUTHORITY ;AEA11-022SUSITNA-WATANA HYDRO 43-1404-TM-031014 Clean,reliable energy for the next 100 years.CEll Figure B 5.2008 North Iwate Earthquake Mainshock and aftershocks with respect to the Pacific Slab. This is a typical downdip-extension earthquake at the lower plane of the double seismic zone in the Pacific Slab.(Suzuki et al,2009).oo...eesessscscesceseesecsseccessssesscssecseseessessessessssccessecsssessseesesseesessesassaesenees 6 Figure B 6.1949 Olympia Washington Earthquake Locations and mechanisms of the historical and modern Puget Sound intraslab earthquakes.The contours show the depth to the top of the subducting Juan de Fuca plate.(Ichinose et al,2006)............cs ssesssesesccescssceseseessssesscescceesecencceesssesssseseecnseeesecsacensesseaceeese 7 Figure B 7.1949 Olympia Washington Earthquake Juan de Fuca plate boundaries determined from seismic reflection approximately one degree north of the 1949 Olympia,Washington earthquake. (Creager et al,2002),0...ceesccsssesscessscccesescessccsesscccesssscesssscessseseesssssessesesenecsesseeceessesseceseesseessasessssnssessseates 7 Figure B 8.1997 Michoacan and 1999 Oaxaca Earthquakes Tectonic map and contours showing the depth to the top of the Cocos Plate.Cross sections show the top of the Cocos Plate with respect to the regional Intra-Slab earthquakes.(Singh et al,2002).0....sssscsssscsssccssssssersesssssesssscsseecsseeseessseesesesessseeseeseees 8 Figure B 9.1997 Michoacan Earthquake Map showing the source mechanism and a schematic of the fault plane with respect to the Cocos Plate.(Hernandez et al,2001)........ee teeeseseeeeeeneeeeseeesetetseetscsesseeesessees 9 Figure B 10.2001 El Salvador Earthquake Cross section showing the preferred source solution of the El Salvador earthquake plotted with the regional seismicity and a line showing the top of the Cocos Plate. The bottom figure is a tectonic interpretation of the earthquake (Vallee et al.,2003).0.0...eesssssseeseeeeeees 10 Figure B 11.2005 Tarpaca Earthquake Cross section showing the geometry of the Nazca Plate used in the MWH (2012)hazard report.........eeecessesceseeseesesecesceseeeessesceseessessesssceesececessseccssessescesessseeseacssseseseeseeeeeeegs 11 Figure B 12.2005 Tarpaca Earthquake Cross section showing the geometry of the Nazca plate,the preferred rupture plane of the 2005 Tarpaca earthquake,aftershocks (dark blue circles),and background seismicity (light blue circles)(Peyrat et al.,2006).0...ccscsessssssssssssssssssssesssssssssessssssesessssesssseseessseeeseesers 11 REVIEW COPY Page iii 03/10/14 --Z--ALASKA ENERGY AUTHORITY -WATANA HYDR AEA11-022SUSITNA-WATA O 13-1404-TM-031014 Clean,reliable energy for the next 100 years.CEIl 1.SYNOPSIS This report documents the selection of an appropriate epsilon value for the Susitna-Watana site,and proposes the choice of a half sigma,based on the conditions at the site and the rarity of the deterministic event chosen.Seismic hazard analyses completed to date indicate that the governing seismic event will occur in the subduction zone associated with an intraslab rupture.The discussion focuses exclusively on the intraslab source and is intended to aid in the selection of design criteria for the structural analysis of the Susitna-Watana Dam.The memo explains the rationale for the selection of an epsilon value of 0.5 (69th percentile of a lognormal distribution)for a controlling intraslab event. The examination of the specific conditions at the Susitna-Watana site has been facilitated because of similar previous work performed for the Chucapaca Project Management Feasibility Study in Peru where the subduction zone conditions are very similar to those prevailing at Susitna-Watana.That analysis was well received and implemented.The conditions at Susitna-Watana are similar in that both projects are situated above and at similar locations with respect to the intraslab:the Chucapaca project has a hypocentral distance of 120 km and a hypocentral depth of 100 km,the Susitna-Watana project has a hypocentral distance of 62 km and a hypocentral depth of 60 km.MWH has therefore been able to use a substantial part of the analysis prepared by Norm Abrahamson for the Chucapaca Project. MWH has adjusted the Chucapaca analysis to address the specific conditions at the Susitna-Watana Project; In order to understand the selection of an appropriate epsilon value for the Susitna-Watana dam site,it is important to understand how the project-specific distance parameters were developed for a specific ground motion prediction equation (GMPE)and how to correctly apply them in practice. GMPEs are equations that predict the expected ground motion at a site.The three most important input parameters into a GMPE are:distance (closest distance from the site to the earthquake rupture, hypocenter,or vertical projection of the fault plane),magnitude (a measure of the strength of the earthquake),and epsilon (a statistical value).This discussion focuses on these three parameters. Magnitude of potential events can be estimated from the potential rupture area.The rupture area is calculated from the length and width of the fault (A=LxW).The length of the fault is measured from end to end as it would be indicated on a map.Although the seismic monitoring network set up for the Susitna-Watana project has provided an excellent clarification of the spatial arrangement of the subducting plate,the width/depth of the fault is more challenging to estimate because it requires that the angle of the rupture be known.A literature review to document the possible angles at which the intraslab ruptures is included in this memorandum. The GMPEs used in the study are based on hypocentral distance and hypocentral depth,instead of using the rupture distance.There can be many different hypocentral distances and hypocentral depths REVIEW COPY Page 1 03/10/14 -Z-ALASKA ENERGY AUTHORITY ;AEA11-022SUSITNA-WATANA HYDRO 43-1404-TM-031014 Clean,reliable energy for the next 100 years.CEIl for a given rupture area.Given that deterministic calculations should be the closest distance to the rupture,significantly different peak ground acceleration (PGA)values may be obtained if the hypocentral distance along the rupture plane is varied. Ground motions from a GMPE are presented as a median value and standard deviation of a lognormal distribution.Epsilon is the number of standard deviations that the natural log of a particular ground motion value is above or below the natural log of the median value.The choice of epsilon facilitates a decision on the acceptable level of risk.FERC guidelines suggest a one sigma deviation above the median,(i.e.the 84th percentile)be used for estimating the ground motions (Idriss &Archuleta,2007), but it must be recognized that this choice results in a 16%chance that there will be higher ground motions than this assumption.There are cases -for example in California -when different epsilon values are accepted.It is important to point out that the choice of epsilon does not account for the probability that a particular event will occur.Instead,it only takes into account the level of ground motions if the event does occur. It is proposed that an epsilon value of 0.5 (corresponding to the 69""-percentile values)be selected for the intraslab earthquake ground motions.The GMPEs are based on hypocentral distance and hypocentral depth,instead of using the distance to the rupture plane.One rupture plane for an intraslab event could have many different hypocentral distances and hypocentral depths.If the hypocenter is randomized on a rupture plane,then the average of the 84"percentile ground motions corresponds to the 69"percentile with the closest hypocentral distance.It is proposed in this paper that 0.5 sigma be used for the deterministic analysis for slab events if a large (M8)magnitude is used for the maximum credible earthquake (MCE).If a smaller magnitude (M7.5)is used for the MCE,then the 84th percentile is appropriate. REVIEW COPY Page 2 03/10/14 ---Z-ALASKA ENERGY AUTHORITY ITNA-WATANA HYDRO AEA11-022SUS13-1404-TM-031014 Clean,reliable energy for the next 100 years.CEI 2.INTRODUCTION There are a number of different models available for calculation of the ground motions from intraslab events. For the BC Hydro model,hypocentral distance is used as the distance metric for slab events rather than rupture distance because rupture distance was not available for most of the large magnitude slab events. For the Atkinson and Boore (2003)model and for the Zhao et al.(2006)model,the distance metrics are given as closest distances (fault distance and source distance,respectively);however,for slab events, the rupture distance is not well defined.Gail Atkinson and John Zhao were both involved in the BC Hydro ground motion study and provided their data for inclusion in the BC Hydro data set.During the BC Hydro study to update seismic understanding and prepare uniform criteria,they both indicated that the slab distances were mostly hypocentral distances. Given that the GMPEs are based mainly on hypocentral distance for slab events,there is an issue for the application of these models to large magnitude slab events in a deterministic analysis such as the Susitna-Watana case.In particular,the deterministic approach assumes that the rupture is located at the shortest distance to the site,but that does not mean that the hypocenter will be at the closest point. Figure 1 illustrates the case where the hypocenter is located at the closest point.The hypocenter may be located anywhere along the rupture.It is very unlikely that the hypocenter will be at the closest distance to rupture. To evaluate the ground motion for a minimum rupture distance,the ground motion can be computed for a suite of hypocenter locations randomly located on the rupture plane.This leads to an average hypocenter distance that will be larger than the rupture distance.This approach is dependent on the rupture dimension (length and width). For interface earthquakes,the rupture plane is along the top of the slab at the interface between the subducting slab and the overriding continental crust (Figure 1).The rupture geometry of large interface earthquakes is straightforward with a rupture width set from the trench to bottom of the interface (about 50 km depth).In contrast,for slab events,the rupture geometry is not obvious from just the slab geometry.The rupture orientation could be near vertical with a narrow rupture width or the rupture could have a shallower dip with a wide rupture width (see Figure 1). To understand how large intraslab events rupture (narrow or wide),rupture geometries for past slab events around the world were compiled. REVIEW COPY Page 3 03/10/14 Zz ALASKA ENERGY AUTHORITY SUSITNA-WATANA HYDRO AEA11-022 13-1404-TM-031014 Clean,reliable energy for the next 100 years.CEIl Surface A Hypocentral Depth Interface Intraslab Possible Slab Ruptures Figure 1.Example of Rupture Geometries of Slab earthquakes,both Narrow and Wide Ruptures are shown.Based on AEIC dip angle of 25 degrees and WSN 2 sigma width of 12.3km (Fugro,2013). 2.1 Purpose For the intraslab event a single rupture plane could initiate from any one point located on that plane,it does not necessarily have to be the location closest to the project site.Given the significant rupture dimensions for a large magnitude event ( 10,000 km?)it would be very rare that the slab would rupture at the exact point located at the closest distance to the project site.The purpose of this technical memorandum is to illustrate the inconsistences between the distance metrics used as input into the GMPEs for an intraslab event.The various ground motions resulting from a single rupture surface will be analyzed to develop a consistent approach in selecting appropriate ground motions which fit into the well-established deterministic framework. 2.2 Procedure The procedure for selection of an appropriate level of ground motion for the project is as follows: °Literature review to determine dimensions of previous intraslab ruptures fe)Dip with respect to intraslab °Aspect ratio REVIEW COPY Page 4 03/10/14 ,ALASKA ENERGY AUTHORITY SUSITNA-WATANA HYDRO AEA11-022 13-1404-TM-031014 Clean,reliable energy for the next 100 years.CEll °Consideration of maximum magnitude °Selection of magnitude-area relationship °Calculations to determine rupture area and geometry to model rupture on intraslab °Hypocentral distance and depth calculations for three potential rupture planes with uniformlydistributedhypocenterslocateddirectlybeneathprojectsite e Calculations of peak ground acceleration resulting from various hypocenters identified in the bullet above. °Comparison of peak ground acceleration and recommendation for appropriate ground motion level (epsilon). REVIEW COPY Page 5 03/10/14 -Z-ALASKA ENERGY AUTHORITY ;AEA11-022SUSITNA-WATANA HYDRO 43-1404-TM-031014 Clean,reliable energy for the next 100 years.CEI 3.RUPTURE GEOMETRIES FOR LARGE SLAB EARTHQUAKES Finite-source inversions are routinely estimated for larger magnitude earthquakes,but source inversions are less common for large slab earthquakes.An initial literature review discovered a total of nine large magnitude slab earthquakes with both finite-fault solutions as well as information on the subducting slab geometry readily available (Table 1).For some earthquakes,there are multiple source inversions published so they are entered in the table more than once. The inverted rupture planes of these earthquakes were reviewed to determine how intraslab earthquakes rupture the slab.Table 2 summarizes the finite-fault solutions.The finite-fault solutions are summarized in Appendix A,and figures illustrating the slab geometries are given in Appendix B. The maximum rupture width is controlled by the dip of the earthquake and the dip of the slab.For example,if the slab dip is 50 degrees and the earthquake dip is 90 degrees,then the rupture will be at 40 degrees with respect to the slab dip,leading to a narrow rupture.In contrast,if the slab dip is 50 degrees and the earthquake dip is 60 degrees,then the rupture will be at 10 degrees with respect to the slab,leading to a wide rupture width.Because the slab dips will vary for different subduction zones, the fault plane dip is not enough information.Therefore,Table 2 includes a column labeled "Dip with respect to slab"which gives the estimates of the fault plane dip with respect to the dip of the slab in the earthquake depth region.These values range from 15 to 77 degrees,with an average of about 45 degrees. In addition,the aspect ratio (length:width)of the rupture surface should be considered.Table 2 includes a column for the aspect ratio and it can be seen that this value ranges from 0.5 to 2.0,with an average of 1.3.Based on the available data the width or length is no larger than about twice as large as the opposite dimension (illustrated by Figure 2). Length WidthFigure 2.[lustration of 2:1 and 1:2 Aspect Ratios (length:width) REVIEW COPY Page 6 03/10/14 ALASKA ENERGY AUTHORITY SUSITNA-WATANA HYDRO AEA11-022 13-1404-TM-031014 Clean,reliable energy for the next 100 years.CEIl Table 1.Slab Events with Finite Source Inversions from Literature Review Event DATE |MAG LAT LON (an),EQNAME |SLABINFO REGION |srzaiot |6.7 |34.129°N |132.696°E |46.46 |2001Geiyo |PhMPpine Seay Japan 1 |3eaio1 |68 |3413°|132.7°|46.46 |2001 Geiyo |PnMppme Seal Japan seaon |67 #546 |aaor cee PMPRE S|Jepan °°2003 Off-i Northeastern2|5/26/03 |7.1 |38.818°N |141.654°E |72.03 'Miyagi Pacific slab |tionshu,Japan ae |.oo |aaa evo ln aan 2008 North |4. |Northern Iwate,3 |reams |69 |so.739°|14167)|115 |"ivate |Pacific Slab |NOT ..|Puget Sound . °©1949 Olympia,Cascadia4|413/49 |68 47.1 122.7 60 Washington |!Mttasiab ---|susquction zoneJuandeFuca 5 |497.|.7.1..|18.219°|-102.756°|35.|,,1997 |Cocos Plate,|Michoacan,-wea].-Tae |e rg Pe cee Seen Michoacan,|)Intraslab -|- .»Mexico "= 9/30/99 |7.5 |16.059°|-96.931°45 |1999 Oaxaca,|Cocos plate,|g,aca,Mexico 6 Mexico intraslab 9/30/99 |7.5 49 |1999 Oaxaca,|Cocos plate,|gs,aca,MexicoMexicointraslab ae ae go fo of By.2001 El...|Cocos plate,.|eeeOTe113/01 7.7 |13.04%88.66 Les 54.=Galvador |intraslab'%El Salvador- 6/13/05 |7.7 |-19.934°|-69.028°|90--115 |arapaca,Nazca,Chile 8 Chile Intraslab 6/13/05 |7.7 |-20.168°|-69.264°97.6 Tarapaca,Nazca,ChileChileIntraslab 9 |2st |6.8 |47.14°N |122.71°;W |56 {2001 Nisqually}Intrastab-|CascadiaeeeaeeecoePogoaoe|Juan de Fuca nd on zene Puget Sound .10 |4/2965 |66 |47.38°N |122.31°w |60 1988 Seattle Intrasiab-|«cascadaJuandeFucaubductionzone REVIEW COPY Page 7 03/10/14 SUSITNA-WATANA HYDRO Clean,reliable energy for the next 100 years. ALASKA ENERGY AUTHORITY AEA11-022 13-1404-TM-031014 CEIl Table 2.Summary of Finite Fault Solutions for the Selected Intraslab Earthquakes Eqk#EQ NAME LENGTH (km) WIDTH (down dip)(km) AREA (km42) Aspect Ratio Length:Width Top of Rup (km) DIP DIP (WRT Slab)STRIKE REFERENCE 2001 Geiyo 05 =00 AZ 36.46 ©57W NIS1E>_.Asano,lwata,. and Irikura (2004) |2001 Geiyo 30 21 630 1 40 58.5W 180 |_Mai Database: Sekiguchi and "[wata (2002)> 2001 Geiyo.30.18.640.40 "60W ATO _Mai Database:- ©Kakehi (2004) 2003 Off- Miyagi 28 30 840 0.9 63.03 90 (top 9 km),then 69W degrees 40 N190E Asana,Iwata, and Irikura (2004) 2008 North ee Iwate :"SEG1:14SEG2:16 -SEG2: SEG | : 900.30° 30:: os |-e a SEG1:=."saw oe SEG2:. 65W +SEG1: ON179E - 'SEG2: N223E °° "Sezuki,Aoi,and.Sekiguchi (2009) 1949 Olympia, Wash 36 33 1188 1.1 44 15 NOE Ichinose,Thio, and Sommerville (2006) 1997 Michoacan, |:Mexico |50 -30.1500 ee 20 89 M77 105 ae "Santoyo,Singh,_.and Mikumo |. "(2005)" 1999 Oaxaca, Mexico 90 45 4050 2.0 25 50NE 295 Hernandez et al., (2001) 1999 Oaxaca, Mexico 90 45 4050 2.0 22 50NE 295 Mai database: Hernandez et al (2001) REVIEW COPY Page 8 03/10/44 -zy ALASKA ENERGY AUTHORITY SUSITNA-WATANA HYDRO AEA11-022 13-1404-TM-031014Clean,reliable energy for the next 100 years.CEII WIDTH .Top ofLENGTHAREAAspectRatio DIP (WRTEqk#|EQNAME (down ae Rup DIP STRIKE REFERENCE(km)dip)(km)|(*™*2)Length:Width (km)Slab) 2b 901 EP |oe ee ee Se aa 4 |.-Vallee,Bouchon,ST Se "70 60°|42000:|1.2 20.58NE |. 15.-297.|and Schwartz:Salvador :oe eS ae whe ,- ve : ee =(2003)© Tarapaca,50 40 2000 1.3 100 |15W 35 175 Delouis and 3 Chile :Legrand (2007) Tarapaca,-.Peyrat et al.Chile 60 30 1800 2.0 90 24W 44 189 (2006) -1 =20017 en BRE ci'.|Sg : de en .as .Ichinoseet8|Nisqually fo BQ fA A988 PAB BB |15 |755 350.|.al(z004) 1965 10 Seattle-30 20 248 1.5 60 15 55 344 31 (0004),Tacoma . REVIEW COPY Page 9 03/10/14 Zz ALASKA ENERGY AUTHORITY SUSITNA-WATANA HYDRO sata0annn4-022 Clean,reliable energy for the next 100 years.CEIl 4.DETERMINISTIC GROUND MOTION FOR SLAB EVENTS Consideration of Maximum Magnitude The maximum magnitude (Mmax)of Mw 7.5 for intraslab events used in Wesson et al.(2007)and adopted in the Fugro (2012)seismic hazard analysis was too low,given the known occurrence of larger events.This study considers a Mmax for the intraslab equivalent to a 7.8 and 8.0.Additional details on this topic can be found in the Fugro (2013)report titled "Revised Intraslab Model and PSHA Sensitivity Results”. Estimated Rupture Area The project site lies above the McKinley Block,which shows evidence of being physically detached from the Kenai Block (Ruppert and Hansen,2002).The McKinley Block clearly shows a moderately dipping upper section between 50 and 90 km,a generally a more steeply dipping section between 90 and 150 km depth.The parameters for the slab are included in Table 3 and Table 4 below and also shown in plan view and profile view in Figure 3 and Figure 4 (Fugro,2013). Table 3.Slab Plane Parameters Plane Depth Slab SlabNumberLocationRange|Strike |Dip |Thickness:Thickness: .(in)lo(km)=o(km) 1 McKinley Block (AEIC)35.90 58}35 45 9.0 i McKinley Block (WSN)35-90 63 |2 6.2 123 2 Mckunley Block 90-150 52 |50 5.5 10.9 3 McKinley Block 90-115 50 |32 36 7.2 4 McKinley Block 115-150 50 |63 40 19 5 Kenai Block North 40-100 17 |27 78 15.6 6 Kenai Block North 100-150 lif 32 9.2 18.4 7 Kenai Block South 50-200 26 =|46 92 18.3 Table 4.Closest Approach Distances of Intraslab Seismic Source Plane Nearest Distance to Plane Vertical Distance to (km)Plane(km) Best Fit $7.1 62.9 +1 Sigma 54.0 59.5 +2 Sigma 50.9 56.1 REVIEW COPY Page 10 03/10/14 a ALASKA ENERGY AUTHORITY SUSITNA-WATANA HYDRO AEA11-022 13-1404-TM-031014 Clean,reliable energy for the next 100 years.CEIl ppeaigg Theat g TEABODE PHN -F T T T T T T T T a ne 4 -McKinley:3-McKinley:NE 116-150km NE 90-115km 209290 2-McKinley:. SY!90-160km d Reson 6 -Kenai North: een!below 100km Project Site aD teed - ra abeAMIELTENDGrande pong CoeTISESDEwevewatt"gescbuc aout ees Par22800ganna View looking NNE.1 i 1 3 L 4 rt '3154183152"154 -150 140 "149 "147 o14€ Longitude Figure 3.Slab Planes,three dimensional figure shown on the left for McKinley Block (planes 1-4)and plan view of all planes shown on the right.(Fugro,2013) REVIEW COPY Page 11 03/10/14 2 ALASKA ENERGY AUTHORITY SUSITNA-WATANA HYDRO AEA11-022 ;13-1404-TM-031014 Clean,reliable energy for the next 100 years.CEll A x Dam Site ; & %*nPfxzoeLtFyLene2fidABEL| *-"° e eke Si L Depth(km)eo2'eet;on7+.-%as*100 T T 0 20 40 60 80 100 120 140 Figure 4.Recorded seismicity from locally installed seismometers that show Intraslab plane in profile.(Fugro,2013).Vertical and horizontal standard location errors shown. REVIEW COPY Page 12 03/10/14 Ze ALASKA ENERGY AUTHORITY AEA11-022SUSITNA-WATANA HYDRO sataoa nh 022 Clean,reliable energy for the next 100 years.CEIl 6 100 206 306 Figure 5.AEI Seismicity and Location of Slab Planes,grid with correlation distance of 15km (Fugro,2013) Determination of potential slab rupture planes requires that the geometry of past intraslab ruptures be evaluated.The aspect ratio (length:width)is included in Table 2.The average aspect ratio from those events listed in Table 2 is 1.3,with a maximum ratio of 2 and a minimum ratio of 0.5.An aspect ratio of 1.5 was selected to be a reasonable value for this analysis.The length of the McKinley Block is approximately 200 km (see Figure 5).Even if the highest aspect ratio of 2 is used to estimate size of the rupture plane,the proposed rupture would not extend through the McKinley Block In order to model the rupture plane a dip with respect to the slab must also be selected.The average value from those included in Table 2 is 45 degrees,with a maximum dip with respect to the slab of 77 degrees and a minimum value of 15 degrees.A value of 45 degrees for the dip with respect to the slab was selected for this study. REVIEW COPY Page 13 03/10/14 Zz ALASKA ENERGY AUTHORITY ;AEA11-022SUSITNA-WATANA HYDRO 43-1404-TM-031014 Clean,reliable energy for the next 100 years.CEIl The maximum area can be calculated for a magnitude 7.8 and 8.0 using the following rupture area- magnitude relation proposed by Abe (1981): Log(A)=M -3.95 The Abe (1981)relationship was compared to Wells &Coppersmith (1994)for all fault types and also a Geomatrix (1993)relationship developed by Youngs for large subduction zone events.The empirical relationships are plotted in Figure 6 against the data obtained in Table 2.Figure 6 illustrates that,for a magnitude of 7.8 to 8.0,the Abe (1981)relationship falls in between the Wells &Coppersmith (1994) and the Youngs relationship (Geomatrix,1993).At the magnitude range used in this study,there is very little sensitivity to the relationship selected to estimate rupture area.The Abe (1981)relationship was selected for use in this study. 8.50 8.00 Ye r)A7.50 Y XKMagnitudeo7.00 araosHale @ Earthquakes in Table2 e|2 -Abe 1981 6.50 ==Youngs ome \WC94 6.00 LU ||Titi 100 1000 10000 100000 Area (km2) Figure 6.Magnitude-Area Scaling Relationship Comparison Using the Abe (1981)relationship for a magnitude 7.8 event,the rupture area would equate to 7,080 km?.Then applying a length:width aspect ratio of 1.5,along with a dip with respect to the slab of 45 degrees the length and width are calculated to 103 km and 69 km,respectively.It should be noted that the down dip rupture width of 69 km would rupture through the width of the zone of small earthquakes in Table 3 for the WSN McKinley Block equal to 12.3 km for 2c. REVIEW COPY Page 14 03/10/14 Zz ALASKA ENERGY AUTHORITY SUSITNA-WATANA HYDRO AEA11-022 . 13-1404-TM-031014 Clean,reliable energy for the next 100 years.CEI If the same approach is taken for a magnitude 8.0,the area would equate to 11,200 km'with a length | equal to 130 km and down-dip rupture width of 86 km. Table 5.Rupture Geometry for M7.8 and M8.0 WIDTH :Closest DIPMagnitudemesh(down dip)(emr2)ASP anes Distance to Site (WRT (km)engin-Wi (km)'Slab) TB 103 3 69}7080 >1.5.ae 50.9 45 8 130 86 11200 1.5 50.9 45 Notes:1:Taken from Table 4 for +2 sigma. For a deterministic analysis,the closest rupture distance for an earthquake is used;however for the intraslab GMPEs,the closest rupture plane distance is not included in the model,only the hypocentral distance and hypocentral depth.Because the location of future hypocenters on the fault cannot be predicted,it is necessary to distribute potential hypocenters uniformly on potential fault planes. Therefore,magnitude 7.8 event and a magnitude 8.0 event were evaluated by placing potential hypocenters on three potential fault planes with a dip with respect to the slab equal to 45 degrees and hypocenters distributed over the rupture plane for three depths (1/6,1/2,and 5/6 of the rupture width) and for nine locations along strike between 10%and 90%of the rupture length (Table 6,Figure 7 and Figure 8).The rupture plane is overlaid on Figures 7 and 8,for added clarity Rupture Scenarios for a M8.0 event 80.0 ror ere __70.0 {ol |le |Ie ollie tid §00 a B 50.0 =Fao 1ell oi @ lie |io!|wl |lei lea @ 30.0 £ §20.0 a 10.0 tg »>¢¢¢¢¢ 0.0 -60.0 -40.0 -20.0 0.0 20.0 40.0 60.0 Distance Parallel to Trench (km) Figure 7,Locations of Hypocenters on the Rupture Plane for an M8 Slab Earthquake REVIEW COPY Page 15 03/10/14 yw SUSITNA-WATANA HYDRO Clean,reliable energy for the next 100 years. ALASKA ENERGY AUTHORITY AEA11-022 13-1404-TM-031014 CEll Rupture Scenarios for a M7.8 Event 80.0 PEt RRR __70.0§60.0er Teo ee eT ie ey lel Q 50.0 £ 2 40.0a)o/)oO io]m1]ie ol ie)@230.0 :S§20.0 ;”10.0 %|©$f PH o] 0.0 aes ee +rf it -60.0 -40.0 -20.0 0.0 20.0 40.0 Distance Parallel to Trench (km) 60.0 Figure 8.Locations of Hypocenters on the Rupture Plane for an M7.8 Slab Earthquake Two-thirds of the rupture down-dip width (5/6-1/6)and 80%of the rupture length is used to uniformly distribute the hypocenters.The rupture plane is located at three locations (at the closest hypocentral distance to the site,and shifted +30 or +25 km up and down the slab),illustrated in Figure 9 for a magnitude 8.0 event.A magnitude 7.8 event would have a smaller rupture plane and in order to place them end to end a smaller distance of 25 km was used,compared to 30 km for a magnitude 8.0. REVIEW COPY Page 16 03/10/14 -Z-ALASKA ENERGY AUTHORITY AEA11-022SUSITNA-WATANA HYDRO sactana ett 022 Clean,reliable energy for the next 100 years.CEIl Surface A Site ' \ 'Hypocentral Depth' ' ' t ( ( ( t 't Hypocentral Distance \t i i t ' t } t 7]t i} Possible Slab Ruptures NOT TO SCALE Figure 9.Possible Slab Ruptures for a Magnitude 8 event,red star illustrates the hypocenter with the closest distance.(Blue diamonds represent uniformly distributed hypocenters (see Figure 7)for a M8.0 earthquake) Using the BCHydro GMPE with a Vs39=1080 m/s and the single-station sigma of 0.58,the 84th percentile PGA was computed for each magnitude,dip,and hypocenter for the Watana site.Assigning equal weight to each hypocenter,the average 84th percentile PGA for a M8.0 event is 0.81 g.For comparison,putting the hypocenter at the closest distance results in an 84th percentile PGA of 1.15 g. Using 0.5 sigma,with the hypocenter at the closest distance,results in a PGA of 0.86g.Using the same approach for a magnitude 7.8,the 84"percentile PGA with equally weighted hypocenters would be 0.80g,the 84"percentile PGA at the closest distance is 1.09 g,and the 69"percentile at the closest distance is 0.81 g.For comparison,using a smaller magnitude of M7.5 for the deterministic source, which was common practice previously,leads to a PGA of 0.76 g.All results are summarized in Table 7. REVIEW COPY Page 17 03/10/14 ym SUSITNA-WATANA HYDRO Clean,reliable energy for the next 100 years. ALASKA ENERGY AUTHORITY AEA11-022 13-1404-TM-031014 CEIl Table 6.Hypocentral Depths and Distances for M7.8 &M8.0 Events Rupture Magnitude 7.8 Magnitude 8.0Plane'Distance Distance Hypocentral Rupture Hypocentral Median Distance Distance Hypocentral Rupture Hypocentral Median Down-Paraifle!to Depth (km)*Distance Distance Ground Down-Parallel Depth Distance Distance Ground Dip Trench (km)*(km)*Motion Dip to (km)4 (km)*(km)¢Motion (km)?along Slab (g)(km)?Trench (a)Strike(km)*(km)? 11.4 41.2 45.9 57.1 74.1 0.36 14.4 51.9 45.9 60.5 83.2 0.33 11.4 30.9 45.9 57.1 68.9 0.40 14.4 38.9 45.9 60.5 75.8 0.37 11.4 20.6 45.9 57.1 65.0 0.44 14.4 25.9 45.9 60.5 70.1 0.42 11.4 10.3 45.9 57.1 62.5 0.46 14.4 13.0 45.9 60.5 66.4 0.45 11.4 0.0 45.9 57.1 61.6 0.47 14.4 0.0 45.9 60.5 65.1 0.46 11.4 -10.3 45.9 57.1 62.5 0.46 14.4 -13.0 45.9 60.5 66.4 0.45 11.4 -20.6 45.9 57.1 65.0 0.44 14.4 -25.9 45.9 60.5 70.1 0.42 11.4 -30.9 45.9 57.1 68.9 0.40 14.4 -38.9 45.9 60.5 75.8 0.37 %E 11.4 -41.2 45.9 57.1 74.1 0.36 14.4 -51.9 45.9 60.5 83.2 0.33 ce 34.3 41.2 67.5 57.1 85.8 0.38 43.2 51.9 73.0 60.5 96.6 0.37 ge 34.3 30.9 67.5 57.1 81.3 0.42 43.2 38.9 73.0 60.5 90.3 0.41 RS 2 34.3 20.6 67.5 57.1 78.0 0.44 43.2 25.9 73.0 60.5 85.5 0.45 oer 34.3 10.3 67.5 57.1 75.9 0.46 43.2 13.0 73.0 60.5 _82.5 0.47 65 34.3 0.0 67.5 57.1 75.2 0.47 43.2 0.0 73.0 60.5 81.5 0.48 Bo 34.3 -10.3 67.5 57.1 75.9 0.46 43.2 -13.0 73.0 60.5 82.5 0.47 rn S 34.3 -20.6 67.5 57.1 78.0 0.44 43.2 -25.9 73.0 60.5 85.5 0.45 z=34.3 -30.9 67.5 57.1 81.3 0.42 43.2 -38.9 73.0 60.5 90.3 0.41 EE 34.3 41.2 67.5 57.1 85.8 0.38 43.2 -51.9 73.0 60.5 96.6 0.37 re 3 57.2 41.2 89.0 57.1 101.3 0.39 72.4 51.9 100.1 60.5 115.8 0.40 ro 57.2 30.9 89.0 57.1 97.6 0.42 72.1 38.9 100.1 60.5 110.6 0.43 57.2 20.6 89.0 57.1 94.8 0.44 72.4 25.9 100.1 60.5 106.7 0.45 57.2 10.3 89.0 57.1 93.1 0.45 72.1 13.0 100.1 60.5 104.3 0.47 57.2 0.0 89.0 57.1 92.5 0.45 72.1 0.0 100.1 60.5 103.5 0.48 §7.2 -10.3 89.0 57.1 93.1 0.45 12.1 -13.0 100.1 60.5 104.3 0.47 57.2 -20.6 89.0 57.1 94.8 0.44 72.1 -25.9 100.1 60.5 106.7 0.45 57.2 -30.9 89.0 57.1 97.6 0.42 72.1 -38.9 100.1 60.5 110.6 0.43 57.2 -41.2 89.0 57.4 101.3 0.39 72.1 -51.9 100.1 60.5 115.8 0.40 REVIEW COPY Page 18 03/10/14 Zz ALASKA ENERGY AUTHORITY ;AEA11-022SUSITNA-WATANA HYDRO 43-1404-TM-031014 Clean,reliable energy for the next 100 years.CEIl Rupture Magnitude 7.8 Magnitude 8.0 Plane'Distance Distance Hypocentral Rupture Hypocentral Median Distance Distance Hypocentral Rupture Hypocentral Median 2 Down-Parallel to Depth (km)®Distance Distance Ground Down-Parallel Depth (km)?Distance Distance Ground Dip Trench (km)?(km)*Motion Dip to (km)?(km)*Motion (km)'along Stab (g)(km)?Trench (g) Strike(km)'(km)? 11.4 41.2 56.9 50.9 72.4 0.43 14.4 51.9 59.7 50.9 80.8 0.41. 11.4 30.9 56.9 50.9 67.1 0.48 14.4 38.9 59.7 50.9 73.1 0.47 11.4 20.6 56.9 50.9 63.0 0.52 14.4 25.9 59.7 50.9 67.1 0.53 11.4 10.3 56.9 50.9 60.4 0.56 14.4 13.0 59.7 50.9 63.3 0.58 11.4 0.0 56.9 50.9 59.5 0.57 14.4 0.0 59.7 50.9 61.9 0.59 11.4 -10.3 56.9 50.9 60.4 0.56 14.4 -13.0 59.7 50.9 63.3 0.58 11.4 -20.6 56.9 50.9 63.0 0.52 14.4 -25.9 59.7 50.9 67.1 0.53 11.4 -30.9 56.9 50.9 67.1 0.48 14.4 -38.9 59.7 50.9 73.1 0.47 w 11.4 -41.2 56.9 50.9 72.4 0.43 14.4 -51.9 59.7 50.9 80.8 0.41 <34.3 41.2 78.4 50.9 89.1 0.42 43.2 51.9 86.8 50.9 101.3 0.41 £34.3 30.9 78.4 50.9 84.8 0.45 43.2 38.9 86.8 50.9 95.3 0.45 6 34.3 20.6 78.4 50.9 81.7 0.48 43.2 25.9 86.8 50.9 90.8 0.49 5 34.3 10.3 78.4 50.9 79.7 0.49 43.2 13.0 86.8 50.9 88.0 0.51 a 34.3 0.0 78.4 50.9 79.0 0.50 43.2 0.0 86.8 50.9 87.0 0.52 «34.3 -10.3 78.4 50.9 79.7 0.49 43.2 -13.0 86.8 50.9 88.0 0.51 rf 34.3 -20.6 78.4 50.9 81.7 0.48 43.2 -25.9 86.8 50.9 90.8 0.49 S 34.3 -30.9 78.4 50.9 84.8 0.45 43.2 -38.9 86.8 50.9 95.3 0.45 bd 34.3 -41.2 78.4 50.9 89.1 0.42 43.2 -51.9 86.8 50.9 101.3 0.41 $7.2 41.2 99.9 50.9 108.1 0.41 72.1 51.9 113.9 50.9 125.2 0.42 $7.2 30.9 99.9 50.9 104.6 0.43 72.1 38.9 113.9 50.9 120.4 0.45 57.2 20.6 99.9 50.9 102.0 0.45 72.1 25.9 113.9 50.9 116.8 0.47 57.2 10.3 99.9 50.9 100.5 0.46 72.1 13.0 113.9 50.9 114.6 0.49 57.2 0.0 99.9 50.9 99.9 0.46 72.1 0.0 113.9 50.9 113.9 0.49 $7.2 -10.3 99.9 50.9 100.5 0.46 72,1 -13.0 113.9 50.9 114.6 0.49 $7.2 -20.6 99.9 50.9 102.0 0.45 72.1 -25.9 113.9 50.9 116.8 0.47 57.2 -30.9 99.9 50.9 104.6 0.43 72.1 -38.9 113.9 50.9 120.4 0.45 57.2 -41.2 99.9 50.9 108.1 0.41 72.1 -51.9 113.9 50.9 125.2 0.42 REVIEW COPY Page 19 03/10/14 2 ALASKA ENERGY AUTHORITY .AEA11-022SUSITNA-WATANA HYDRO 43-4404-1M-031014 Clean,reliable energy for the next 100 years.CEll Rupture Magnitude 7.8 Magnitude 8.0 Plane'Distance Distance Hypocentral Rupture Hypocentral Median Distance Distance Hypocentral Rupture Hypocentral Median 3 Down-Parallel to Depth (km)°Distance Distance Ground Down-Parallel Depth (km)3 Distance Distance Ground Dip Trench (km)*(km)*Motion Dip to (km)?(km)?Motion (km)'along Slab (9)(km)?Trench (g) Strike(km)'(km)? 11.4 41.2 67.8 57.1 79.6 0.43 14.4 51.9 73.5 60.5 90.9 0.41 11.4 30.9 67.8 57.1 74.8 0.47 14.4 38.9 73.5 60.5 84.2 0.46 11.4 20.6 67.8 57.1 71.2 0.51 14.4 25.9 73.5 60.5 79.0 0.51 11.4 10.3 67.8 57.1 68.9 0.53 14.4 13.0 73.5 60.5 75.7 0.54 11.4 0.0 67.8 $7.1 68.1 0.54 14.4 0.0 73.5 60.5 74.6 0.55 11.4 -10.3 67.8 57.1 68.9 0.53 14.4 -13.0 73.5 60.5 75.7 0.54 11.4 -20.6 67.8 57.1 71.2 0.51 14.4 -25.9 73.5 60.5 79.0 0.51 11.4 -30.9 67.8 57.1 74.8 0.47 14.4 -38.9 73.5 60.5 84.2 0.46 22 11.4 -41.2 67.8 57.1 79.6 0.43 14.4 -51.9 73.5 60.5 90.9 0.41 <<34.3 41.2 89.4 S71 99.4 0.41 43.2 51.9 100.6 60.5 115.4 0.40 fe 34.3 30.9 89.4 57.1 95.6 0.43 43.2 38.9 100.6 60.5 110.2 0.43 £rs 34.3 20.6 89.4 57.1 92.7 0.45 43.2 25.9 100.6 60.5 106.3 0.46 bo oD 34.3 10.3 89.4 57.1 91.0 0.47 43.2 13.0 100.6 60.5 103.9 0.48 2 2 34.3 0.0 89.4 57.1 90.4 0.47 43.2 0.0 100.6 60.5 103.1 0.48 ono 34.3 -10.3 89.4 57.1 91.0 0.47 43.2 -13.0 100.6 60.5 103.9 0.48 5 cS 34.3 -20.6 89.4 57.1 92.7 0.45 43.2 -25.9 100.6 60.5 106.3 0.46 EE 34.3 -30.9 89.4 57.1 95.6 0.43 43.2 -38.9 100.6 60.5 110.2 0.43 nS 34.3 -41.2 89.4 57.1 99.4 0.41 43.2 -51.9 100.6 60.5 115.4 0.40 3 F 57.2 41.2 110.9 57.1 120.2 0.40 72.1 51.9 127.6 60.5 141.6 0.41 57.2 30.9 110.9 57.1 117.1 0.41 72.1 38.9 127.6 60.5 137.4 0.43 57.2 20.6 110.9 57.1 114.8 0.43 72.1 25.9 127.6 60.5 134.3 0.45 57.2 10.3 110.9 $7.1 113.4 0.44 72.1 13.0 127.6 60.5 132.4 0.46 57.2 0.0 110.9 57.1 113.0 0.44 72.1 0.0 127.6 60.5 131.8 0.46 57.2 -10.3 110.9 57.1 113.4 0.44 72.1 -13.0 127.6 60.5 132.4 0.46 57.2 -20.6 110.9 57.1 114.8 0.43 72.1 -25.9 127.6 60.5 134.3 0.45 57.2 -30.9 110.9 57.1 117.1 0.41 72.1 -38.9 127.6 60.5 137.4 0.43 57.2 -41.2 110.9 57.1 120.2 0.40 72.1 -51.9 127.6 60.5 141.6 0.41 Notes: 1:Rupture planes as labeled in Figure 8 2:As shown in Figure 5.Two dimensional space.A distance of 0,for the Distance Parallel to Trench corresponds fo the closest distance. 3:As shown in Figure 6. 4:Three dimensional space. REVIEW COPY Page 20 03/10/14 Zw SUSITNA-WATANA HYDRO Clean,reliable energy for the next 100 years. ALASKA ENERGY AUTHORITY AEA11-022 13-1404-TM-031014 CEll Table 7.Comparison of Deterministic Ground Motion Computed using Different Approaches Rupture plane Hypocenter Magnitude ground motion PGA (g) Hypocenter Located at the assumed to be 7.8 th ,1.09g closest distance at the closest 8.0 84"percentile 1.15g distance Hypocenter Located at the assumed to be 7.8 69"percentile 0.81g closest distance at the closest 8.0 (0.5 sigma)0.86g distance Hypocenters uniformlyOrcatedanedistributedon oO 84"percentile jet.the rupture 'org plane Hypocenter Located at the assumed to be th ' closest distance at the closest 75 84"percentile 0.769 distance REVIEW COPY Page 21 03/10/14 -Z-ALASKA ENERGY AUTHORITY ;AEA11-022SUSITNA-WATANA HYDRO 13-1404-TM-031014CEllClean,reliable energy for the next 100 years. 5.CONCLUSION The GMPEs that will be used for the intraslab events are based on hypocentral distance and hypocentral depth and not the distance to the rupture plane.Deterministic calculations are based on the rupture distance,which -as shown -can result in significantly different PGA values.The 84”percentile deterministic PGA for a M8.0 event,with uniformly distributed hypocenters along the rupture plane, results in 0.81g,whereas if the closest rupture distance is used exclusively,then the resulting PGA 84" percentile for the closest rupture distance is 1.15g.,which is about 0.34g higher.For a magnitude 7.8 event,the resulting difference is similar 0.29g (1.09-0.80).See Table 7 for a summary of the values. The selection of epsilon in deterministic calculations allows for the choice of the level of ground motion that is appropriate for a given situation.Selection of an epsilon lower than unity is not without precedent.The California Division of Safety of Dams (DSOD)allows for a choice of epsilon -in their Consequence Hazard Matrix -for sites located near high,low,or moderate slip rate faults (see Figure 10 for more information).This practice was implemented by the DSOD to address the varying levels of conservatism for deterministically derived parameters.For example,the DSOD will allow the epsilon value to be between 0 and 1 for a low slip rate fault near a dam with extreme consequences,when engineering judgment and a probabilistic seismic hazard analyses are used to select the appropriate level for design.Although the issue at Susitna-Watana relates to the intraslab events -and does not deal with a low slip rate fault -the Californian experience illustrates that there are issues to address in applying a blanket deterministic criteria to any dam. REVIEW COPY Page 22 03/10/14 -y ALASKA ENERGY AUTHORITY AEA11-022SUSITNA-WATANA HYDRO sataneht022 Clean,reliable energy for the next 100 years.CEIl Very High High Slip Moderate Low Slip Slip Rate Rate Slip Rate Rate 9 or greater $9 tol.mm/yr 1.0t00..mmr |less than 0.1 mmr rom'vr ExtremeConsequence g4ih gqin gg4th 50"to Total Class Weight gq 31-36 Highconsequence}4"|94"|50"to |50"to Total Class Weight 84h 84th 19-30 Moderateconsequence}84"|50"to |50™to |50"TotalClass Weiss g4th gah LowConsequence 59"59 50"50" Tora Class Weight Figure 10.California DSOD Consequence-Hazard Matrix It is acknowledged therefore that the use of a standard +1 sigma (34"percentile)is not always the appropriate value for design,and that the selection of sigma values should include a thoughtful analysis of the overall situation.For the controlling intraslab event at Susitna-Watana,the selection of an appropriate sigma is a method to adjust the GMPE so that the deterministic calculations correspond to the closest rupture distance -and not a single point on the most conservative rupture plane.It would be extremely rare that the hypocenter would occur on the closest reach of the intraslab,just as it would beveryrarefora84""percentile motion to be measured at a dam near a fault which is thought to have a low slip rate (see DSOD Consequence Hazard Matrix). In the case of the use of the DSOD's Hazard Matrix,it is required that the deterministic results be compared to a probabilistic seismic hazard analysis. In a similar manner,for Susitna-Watana,the draft probabilistic seismic hazard results were compared to the draft deterministic results (Fugro,2012 and 2013).These preliminary computations by Fugro used the average of several different GMPEs,whereas this analysis only used one GMPE.Therefore results REVIEW COPY Page 23 03/10/14 -Z-ALASKA ENERGY AUTHORITY ;AEA11-022SUSITNA-WATANA HYDRO 43-1404-TM-031014 Clean,reliable energy for the next 100 years.CEIl vary slightly from those computed in this technical memorandum.The comparison performed for the analysis recorded herein is included in Figure 11,and shows that a M8.0 69"percentile (+0.5 sigma) corresponds to a return period of approximately 17,000 years and an 84"percentile (+1.0 sigma) corresponds to about 65,000 years return period. It is proposed that a deterministic event exhibiting a return period of 17,000 years is sufficiently conservative for the project. It should be noted that the preliminary SSSHA available at the time of preparation of this technical memorandum was in draft format and only included a maximum intraslab event of M7.5.A M7.5 has been standard practice as the maximum magnitude that could occur on the intraslab,Wesson et al. (2007)-USGS probabilistic hazard maps for Alaska.However,this is no longer necessarily the case, and the postulated maximum magnitude for intraslab events has increased.The selection of an appropriate maximum magnitude for the intraslab event has not been completed but a sensitivity analysis of the intraslab's maximum magnitude was completed by Fugro,2013.A comparison to these results is included in Figure 12,red lines show how the return period for the intraslab varies based on Mmax for a PGA=0.81g ( 4,000 to 17,000 years).Engineering judgment was used to select a M8.0 to be used in this phase of feasibility design. 10° 2 F 107 Magnitude 8.0 intraslab z 2 PGA=0.81g -69th Percentile 8 g Return Period 17,000 years 3 8zF10°S8a. 3 §Magnitude 8.0 Intraslab5raPGA=1.16g -84th Percentile §E aot Return Period 65,000 years 10° 15 Peak Horizontal Acceleration (g) Source:Hazard Curve:FCL,2012 SHA Deterministic Results:FCL,2013 Figure 11.Comparison to Draft Probabilistic Seismic Hazard Analysis (Fugro,2012). REVIEW COPY Page 24 03/10/14 -y ,ALASKA ENERGY AUTHORITY SUSITNA-WATANA HYDRO AEA11-022 13-1404-TM-031014 Clean,reliable energy for the next 100 years.CEll Mmax Sensitivity @ 1 Fae Or OOS GOS WO RT SO LO TO TON SY Ws NUE WO OW WO Oe 11010eo---Slab Model 1m75 Mmaxke]5 ns btn Stab Model 1:m78 Mmax®2 --=Slab Mode!1m81 Mmax 222103s--PCL (2012)rio 8uw7%>So J Xs §Oo>.3 Xy E 3 22107&:10S a 3 .q a. Q q £oO,5a10°3 @ 3 4 « por] =os]<10 A ee |!0 0.5 1 1.5 2 2.5 Peak Horizontal Acceleration (g) Figure 12.Comparison to Draft Intraslab Sensitivity Analysis (Fugro,2013). Based on the selection of an M8.0 for the intraslab it is recommended that 0.5 sigma be used for the deterministic analysis.If a smaller magnitude (M7.5)is used for the MCE,then the 84th percentile would be more appropriate. REVIEW COPY Page 25 03/10/14 -Z-ALASKA ENERGY AUTHORITY ;AEA11-022SUSITNA-WATANA HYDRO 43-1404-TM-031014 Clean,reliable energy for the next 100 years.CEI 6.REFERENCES Abrahamson,N.A.,Gregor N.,and Addo,K.(2012).BC Hydro Ground Motion Prediction Equations for Subduction Earthquakes,submitted to Earthquake Spectra Asano,Kimiyuki,T.Iwata,and K.Ikikura,Characterization of Source Models of Shallow Intraslab Earthquakes Using Strong Motion Data.13th World Conference on Earthquake Engineering Paper,Vancouver,B.B.,Canada (August 1-6,2004) Creager,Kenneth C.et al.,Three-dimensional reflection image of the subducting Juan de Fuca plate in: The Cascadia Subduction Zone and Related Subduction Systems:Seismic Structure,Intraslab Earthquakes and Processes,and Earthquake Hazards,eds.Stephen Kirby,Kelin Wang,and Susan Dunlop,United States Geological Survey Open -File Report 02---328 (2002). Delouis,Bertrand,D.Legrand,Mw 7.8 Tarpaca intermediate depth earthquake of 13 June 2005 (northern Chile):Fault plane identification and slip distribution by waveform inversion. Geophysical Research Letters,Vol.34,L01304 (2007). Fugro(2013).DRAFT Revised Intraslab Model and PSHA Sensitivity Analysis Results.Susitna-Watana Hydro TM No.XX. Geomatrix (1993),Seismic margin earthquake for the Trojan site:Final unpublished report prepared for Portland General Electric Trojan Nuclear Plant,Rainier,Oregon,Geomatrix Consultants,San Francisco,California. Hernandez,B.et al.,Rupture History of September 30,1999 Intraplate Earthquake of Oaxaca,Mexico (Mw=7.5)from Inversion ofStrong -Motion Data.Geophysical research Letters,Vol.28,No.2 (2001)363 -366. Ichinose,Gene A.,H.Thio,and P.Somerville,Moment Tensor and Rupture Model for the 1949 Olympia,Washington,Earthquake and Scaling Relations for Cascadia and Global Intraslab Earthquakes.Bulletin of the Seismological Society of America,Vol.96,No.3 (2006),1029--- 1037 Idriss,ILM.,and Archuleta,R.J.,2007,Evaluation of earthquake ground motions,draft manuscript for FERC Chapter 13,draft 06.5,http://www.ferc.gov/industries/hydropower/safety/guidelines/eng- guide/chap]3-draft.pdf REVIEW COPY ; Page 26 03/10/14 et a ALASKA ENERGY AUTHORITY ITNA-WATANA HYDR AEA11-022SUSITNAAO13-1404-TM-031014 Clean,reliable energy for the next 100 years.CEll Iwata,Tomotaka and K.Asano,Characterization of the Heterogeneous Source Model of Intraslab Earthquakes Toward Strong Ground Motion Prediction.Pure and Applied Geophysics.168 (2011),117-124. Kakehi,Y.,Analysis of the 2001 Geiyo,Japan,earthquake using high--density strong ground motion data:Detailed rupture process of a slab earthquake in a medium with a large velocity contrast. Journal of Geophysical Research,Vol.109,B08306 (2004). Mai,Martin,Finite Source Rupture Model Database (http://www.seismo.ethz.ch/static/sremod/) Mishra,O.P.,and Dapeng Zhao,Seismic evidence for dehydration embrittlement of the subducting Pacific slab.Geophysical Research Letters,Vol.31,L09610 (2004). MWH (2012).Seismic hazard assessment for Tailings Impoundment Feasibility Level Design,March Nakajima,Junichi and A.Hasegawa.Subduction of the Philippine Sea Slab plate beneath southwestern Japan:Slab geometry and its relationship to arc magnetism.Journal of Geophysical Research, Vol.112,B08306 (2007). Okada,Tomomi,and A.Hasegawa,The M7.1 May 26,2003 off--shore Miyagi Prefacture Earthquake in northeast Japan:Source process and aftershock distribution of an intra--slab event.Earth, Planets,and Space,55 (2003)731-739. Peyrat,S.et al.,Zarpaca intermediate -depth earthquake (Mw 7.7,2005,northern Chile):A slab--pull event with horizontal fault plane constrained from seismologic and geodedic observations. Geophysical Research Letters,Vol.33 (2006). Santoyo,M.A.,S.K.Singh,and T.Mikumo,Source process and stress change associated with the 11 January 1997 (Mw=7.1)Michoacan,Mexico,inslab earthquake.Geofisica Internacional,Vol. 44,4 (2005)317 -330. Singh,Shri K.,V.Kostoglodov,and J.F.Pacheco,Intraslab earthquakes in the subducting oceanic plates below Mexico.In:The Cascadia Subduction Zone and Related Subduction Systems: Seismic Structure,Intraslab Earthquakes and Processes,and Earthquake Hazards,eds.Stephen Kirby,Kelin Wang,and Susan Dunlop,United States Geological Survey Open -File Report 02- --328 (2002). Suzuki,Wataru,S.Aoi,and H.Sekiguchi,Rupture Process of the 2008 Northern Iwate Intraslab Earthquake Derived from Strong--Motion Records.Bulletin of the Seismological Society of America,Vol.99,No.5 (2009),2825-2835. REVIEW COPY Page 27 03/10/14 --Z-ALASKA ENERGY AUTHORITY -WATANA HYDR AEA11-022SUSITNA-WATA O 13-1404-TM-031014 Clean,reliable energy for the next 100 years.CEIl Vallee,Martin,M.Bouchon,and S.Schwartz,The 13 January 2001 El Salvador earthquake:A multidata analysis.Journal of Geophysical research,Vol.108,No.B4 (2003). Wesson,R.L.,Boyd,O.S.,Mueller,C.S.,Bufe,C.G.,Frankel,A.D.,Petersen,M.D.,2007,Revision of time-Independent probabilistic seismic hazard maps for Alaska:U.S.Geological Survey Open-File Report 2007-1043. Xu,Jiren and Y.Kono.Geometry of slab,intraslab stress field and its tectonic implication in the Nankai trough,Japan.Earth Planets and Space,54 (2002)733-742. REVIEW COPY Page 28 03/10/14 a ALASKA ENERGY AUTHORITY AEA11-022SUSITNA-WATANA HYDRO saanaeeAt.022Clean,reliable energy for the next 100 years.CEIl Appendix A: Finite Fault Solutions REVIEW COPY Page A-1 03/10/14 ---Z-ALASKA ENERGY AUTHORITY ;AEA11-022SUSITNA-WATANA HYDRO 43-1404-TM-031014 Clean,reliable energy for the next 100 years.CEIl w+Jove tretvencl ars Sererares vere ererereres Oil=[Dip a7)sO NI8TE]SS §-s et Qa |if OOF Pei}pee Dm |fete;|a J S54 ; 148); |ce nn: 0 5 10 15 20 25 along strike (km) Figure A 1.2001 Geiyo Earthquake (Asano et al.,2004) Geiyo (Japan) S2001GETYO.tsebd Mw EB 017000019 esLawLentrep:24.19",22.70",46.5 ton <Con ue SDP hum ee fey PSS mA re) 5 ? ayj uf Yee (kinj XeoEw [em] Figure A 2.2001 Geiyo Earthquake (Sekiguchi and Iwata,2002)(From Mai Database) REVIEW COPY Page A-2 03/10/14 Za ALASKA ENERGY AUTHORITY ITNA-WATANA HYDRO AEA11-022SUS13-1404-TM-031014 Clean,reliable energy for the next 100 years.CEIl Geiyo (Japan) weer uve naLathentbep:4.59°,192.7; Figure A 3.2001 Geiyo Earthquake (Kakchi,2004)(from Mai Database) heed i i -oarnN190°E -on1[ie 20 [=]1'TmnnaodenlPp es jteas 'nnranDipDirection(km)O20.15 10 5 0 5. Strike Direction (km Figure A 4.2003 Off-Miyage Earthquake (Asano et al,2004) REVIEW COPY Page A-3 03/10/14 SUSITNA-WATANA HYDRO Clean,reliable energy for the next 100 years. ALASKA ENERGY AUTHORITY AEA11-022 13-1404-TM-031014 CEll DistanceDownDipkm(66°E)enDip=65°Northern Segment Southern Segment N359°E ==N179°E N43°E ee N203°E 0 Si -ovr 7 yr te °5 »_©&+©wa ew #oe an be i)o v r wf ©wv &©@ 99 ee .ta rar oar er ee er) a |..-)De ° 15l->ry eee . eo .>*.Oo >. 20).[).: ."19 @)aks 25 .ey .sie ewe ow eo309°5 Oo 5 10 15{km][km]on 2 3!3m Figure4,Slip distribution estimated from waveform inversionusingthetwo-segment model.The rupture started at the hypocenteronthesouthernsegment(open star).The contour interval is 0.5 m.The arrows indicate the amounts and directions of slip.The twosegmentsareconnectedatthepointsshownbytheblackcircles.The three rectangles outlined by the broken line indicate the aspe-sities extracted according to the criterion proposed by Somervilleetal.(1999), Figure A 5.2008 North Iwate Earthquake (from Sazuki et al,2009) 016ah_o.to2peesfete feeswowees43°T vyacee| 4 a jong @ 2.492ahsE &2 1.0 §2 0.5 3 °l 2 0.000a 0 0Distance Along dinke km (NO°E) Figure 8.The 1949 Olympia:earthquake cumulative slip and rake distribution fromthekine 1949 Olympia,Washington M,,=6.8 ve Peak=1.66 m seconds model d by using the multiple-time-windowinversion.The rake vectors point iin the direction of the hanging-wall motion.The hypocenterisat60kmdepthandislocatedat16kmdowndipand20kmalongstrike,The slip-velocity function plotted to the right indicates two pulses of slip.The asperities arelabeled#1 at the byp Figure A 6.1949 Olympia Earthquake (Ichinose et al,2006) and #2 to the south and up-dip relative to the hypocenter, 8 REVIEW COPY Page A-4 03/10/14 Fe ALASKA ENERGY AUTHORITY ;AEA11-022SUSITNA-WATANA HYDRO 43-1404-TM-031014 Clean,reliable energy for the next 100 years,CEIl Fandwidth(lon)+10 t:)w xn bad .a NW Onvtance slong sinke (len)SE Fig.7b.Dislocation pattern obtained from the 2-D kinematic inversion.Stips are chown in cm.The main rupture asperity is located at the $-E portion of the fault plane.Fauk plane is viewed from southwest.Depths arc given ia km.The upper edge of the fault plane is located at adepthof20km. Figure A 7.1997 Michoacan Earthquake (Santoyo et al,2005) Rise time,s Slip amplitude,m Rupture time,s ee = Figure 2.Maps of rise time,slip,and rupture timeobtainedbyinterpolationoftheresultsofnonlinearin- version obtained for the fault geometry correspondingtotheHarvardCMTsolution.The arrows indicate the relative motion of the hanging wall.The star indicates the location of the hypocenter location of the initialmodel. Figure A 8.1999 Oaxaca Earthquake (Hernandez et al,2001) REVIEW COPY Page A-5 03/10/14 Za ,ALASKA ENERGY AUTHORITY SUSITNA-WATANA HYDRO AEA11-022 13-1404-TM-031014 Clean,reliable energy for the next 100 years.CEll Oaxaca (Mexico) Figure A 9.1999 Oaxaca Earthquake (Hernandez et al,2001)(from Mai database). 60°-dipping plane 30°-dipping plane Slip preferred mode!(m)} Rupture velocity preferred model (rvs) 0 20 40 60 6 20 40 60 distance along strike (km toward NW)distance along strike (km toward NW) Figure 6.Preferred rupture models obtained with the extended source analysis.The hypocenter isdenotedbythestar.(top)Slip and (bottom)rupture velocity for (left)60°dipping plane and (right)30°dipping plane.Slip is contoured every I m,and rupture velocity is contoured every 300 ms ',Isochronsoftheonsettimearesuperimposedontherupturevelocitydistributions. Figure A 10.2001 El Salvador Earthquake (Vallee et al.,2003). REVIEW COPY Page A-6 03/10/14 yz SUSITNA-WATANA HYDRO Clean,reliable energy for the next 100 years, ALASKA ENERGY AUTHORITY AEA11-022 13-1404-TM-031014 CEll o coww ic?) ae) = S|K <Are5wnay)=f PE DynaseraOrofgenetaedsercerS:ey ops wi MUR SiaeeeT:AREER 2 fyopSATS7"Apcwin.HonsWARTS:Oy:aAyeySUEptigl211949200458aearts124°"West Longitude 122° Figure 1.Locations and focal mechanisms of 1949 Olympia,1965 Sea-Tac,and 2001 Nisqually earthquakes. The approximate depth to the top of the subducting Juan de Fuca plate are shown as contours. Figure A 11.2001 Nisqually and 1965 Seattle-Tacoma Earthquake (Ichinose et al.2004) REVIEW COPY Page A-7 03/10/14 Zz ALASKA ENERGY AUTHORITY SUSITNA-WATANA HYDRO , AEA11-022 13-1404-TM-031014 Clean,reliable energy for the next 100 years.CEIl Appendix B: Slab Geometries REVIEW COPY Page B-1 03/10/14 -Z-ALASKA ENERGY AUTHORITY SUSITNA-WATANA HYDRO AEA11-022 , 13-1404-TM-031014 Clean,reliable energy for the next 100 years.CEll 1985 1/1 1992 12/31 :M0.0-6.0 N=74551 IVE Kyushu Shikoku Kii Pen.138°E Fig.4.EW cross section of hypocenters of microearthquakes along the Nankai trough.The database is same as in Fig.2. Figure B 1.2001 Geiyo Earthquake Earthquakes in the Philippine Sea Slab (Xu and Kono,2002). REVIEW COPY Page B-2 03/10/14 -y ALASKA ENERGY AUTHORITY SUSITNA-WATANA HYDRO AEA11-022 j 13-1404-TM-031014 Clean,reliable energy for the next 100 years.CEIl 38°130?132°134?136°138*140° 0 200 -400 Depth (km 36°L 32°ae 3G 2001 Gelyo EQ100F*8&.__(Approx.Location)200+ff 300 F 400 A i i.a 02 Figure 2.Distribution of 6187 events used in this study. Colors represent the depth of hypocenters.Hypocenters inthecrosssectionareprojectedontotheA-A'in the map. Figure B 2.2001 Geiyo Earthquake Philippine Sea Slab earthquakes with the approximate location of the 2001 Geiyo earthquake(modified from Nakajima and Hasegawa,2007). REVIEW COPY Page B-3 03/10/14 -Z-ALASKA ENERGY AUTHORITY ITNA-WATANA HYDRO AEA11-022SUSIT13-1404-TM-031014 Clean,reliable energy for the next 100 years.CEIl Figure 2.Cross-sectional velocity images with the distribution of the 2003 Miyagi-oki earthquake aftershocks along the lines (a)A-B,and (b)C-D.(c-d)The same images along the two profiles with the distribution of background seismicity .recorded between October 1997 and October 1998.Smal!white circles denote aftershocks and background seismicity within a 30-km width along the lines A-B and C-D.(e-f)Tomographic images along the same profiles obtained by inverting arrival time data from earthquakes recorded from October 1989 to March 2003 (excluding the 2003 Miyagi-oki earthquake data).The black star and red triangle denote the 26 May 2003 Miyagi-oki main shock and an active volcano (Kurikoma), respectively.The velocity perturbation (in %)scale and locations of the two cross-sections are shown at the bottom.Red triangles in the inset map show the active volcanoes.UBPP abbreviates for the upper boundary of the Pacific plate. Figure B 3.2003 Off-Miyagi Earthquake Structure ofthe Pacific Slab from velocity and earthquakes (aftershocks and background seismicity)in the Pacific Slab (Mishra and Dapeng,2004). REVIEW COPY Page B-4 03/10/14 ya SUSITNA-WATANA HYDRO Clean,reliable energy for the next 100 years. ALASKA ENERGY AUTHORITY AEA11-022 13-1404-TM-031014 CEll '18g Oat 2 "16 u v v T v Lu qT 12 8 4 0 4 8 #12 1 Strike(km)->N18E 141°30'142°00' 39°00°+ 38°30° 6 10 km Fig.3.Aftershock distribution within 1 day of the main shock occurrence.Main shock and aftershocks with magnitude greater than 4.5 are shown by &barge star,medium stars,respectively.(a)Vertical cross section along the strike.(b)Vertical cross section perpendicular to the strike,Bold line denotestheupperboundaryofthesiabestimatedbyZhaoetal.(1997)(c)Epicenter distribution, Figure B 4.2003 Off-Miyagi Earthquake Mainshock and aftershocks with respect to the upper Pacific Plate boundary (Okada and Hasegawa,2003). REVIEW COPY Page B-5 03/10/14 -yw SUSITNA-WATANA HYDRO Clean,reliable energy for the next 100 years. ALASKA ENERGY AUTHORITY AEA11-022 13-1404-TM-031014 CEll (a)41°N a7 & sf)b tort 40°N+_}i AnfspeATHSlt) WiTH2eLe@ wie wgSSNnetPetWwrney | I 50 km Depth[km]S2'1504 :: Magnitude s 4 ”3 * 2 * 200 r r r 140°E W4VE 142°E Figure 1.(a)Map showing the epicenter (star)and strong-motionstations,the records of which were used in this article.Solid symbols denote KiK-net stations grouped as group A (hexagon),group B(square),group C (diamond),group D (circie),and other stations (tri-angle).Open triangles denote K-NET stations.The underlined stationcodesindicatestationswheretheobserveddistinctivephasescouldnotbewellreproducedbythesingle-fault model.We classified thestationsasroughlynorthemandsouthernstations,the station codes ofwhichareshownaboveandbelowthecorrespondingsymbols,re- spectively,White rectangles denote the fault planes of the two-segment model.The source mechanisms determined from P-wave polarity analysis using Hi-nct data and momenttensor inversion usingF-netdataareshownin the inset.(b)Vertical section of the hypocenterdistributiondeterminedbyHi-net.We projected the hypocenterof thecarthquakes(1 January 2001-23 July 2008)in the region shown by the broken rectangle of the upper pane!onto the plane along the east- to-west direction.The open star denotes the mainshock,and the graystarsdenotetheearthquakesthatoccurredthedayfollowingthemain-shock at depths between 90 and 120 km. Figure B 5.2008 North Iwate Earthquake Mainshock and aftershocks with respect to the Pacific Slab.This is a typical downdip-extension earthquake at the lower plane of the double seismic zone in the Pacific Slab.(Suzuki et al,2009). REVIEW COPY Page B-6 03/10/14 --Z-ALASKA ENERGY AUTHORITY SUSITNA-WATANA HYDRO AEA11-022 13-1404-TM-031014 Clean,reliable energy for the next 100 years.CEIl smtp dd Nag Sd dd hdd t el Fi L Locations and mechanisms ofSey"eae fe Ae |historical and modern Puget Sound intraslab earthquakes.The contours from Tréhu et al (2002)show the approximate depth to the top of the subducting Juan de Fuca plate.The depth of these earthquakes is located within0-10 km below the top of this surface.48°NiLATITUDE47°NLu124°W 123°W 122°W LONGITUDE Figure B 6.1949 Olympia Washington Earthquake Locations and mechanisms of the historical and modern Puget Sound intraslabearthquakes.The contours show the depth to the top of the subducting Juan de Fuca plate.(Ichinose et al,2006). Both Surfaces E W Cross Section at 48.0°N .e-™&8&88BDepth(km)8&8&&B90.40.50.60°70 80 90 -400- 110 420430 E W Distance (km)from 124.25°W FIGURE 4:Cross sectional view containing all data collapsed along the north-south direction showing both the upper and lower reflector surfaces.See caption for Figure 3 for an explanation of symbols. Figure B 7.1949 Olympia Washington Earthquake Juan de Fuca plate boundaries determined from seismic reflectionapproximatelyonedegreenorthofthe1949Olympia,Washington earthquake.(Creager et al,2002). REVIEW COPY Page B-7 03/10/14 ---Z-ALASKA ENERGY AUTHORITY: AEA11-022SUSITNA-WATANA HYDRO 43-1404-TM-031014 Clean,reliable energy for the next 100 years.CEll Pou AMAR AAABAR CARES ARSAEAIEABAABADEARODEARASAOBO: ,North American Plate 20-%-¥*XE \P Bay,8 *é 18°F 8 i 16'f -+----Ragcotk 14°F of Cocos Plate 1 sad 'i"n 3 .;dea deal ay 108°-106°104°-102°-100°-94° .Longitude Michoacan -Guerrero Guerrero e%0 ee S 1 a *s °@.Ps 3 oo,”§%%ww o E.- @ ® ®y C)e wo = Distance from the trench axis,km Distance from the trench axis,km Oaxace isthmus ry °° °rd s O °&°6 oO §.oei="bed 2°o oe o ™-C ©2) 6 20 a)'0 e we ry 2Distancefromthewenchaxis,km Distance from the trench axis,km FIGURE 4:Tectonic map of the region.Triangles indicate active volcanoes.All intraslab earthquakes with known focal mechanism ere shown.Relative plate convergence rates are given near arrows along the trench.The numbers above the arrow heads Indicate the age (Myr)of the oceanic lithosphere at the trench.isodepth contours are shown by continuous lines when well defined by seismicity and by dashed lines when inferred.Hypocenters of intraslab earthquakes projected on sections A to D are shown on the four graphs. Figure B 8.1997 Michoacan and 1999 Oaxaca Earthquakes Tectonic map and contours showing the depth to the top of the Cocos @Plate.Cross sections show the top of the Cocos Plate with respect to the regional Intra-Slab earthquakes.(Singh et al,2002). REVIEW COPY Page B-8 03/10/14 Zz ALASKA ENERGY AUTHORITY SUSITNA-WATANA HYDRO AEA11-022 13-1404-TM-031014Clean,reliable energy for the next 100 years.CEll Fc IE CRP I =-_ck oe 91 A sy BiTTSsaNorthamericaplatefi:Cocos plate X&tee 5Pe iNeed y Figure 1.Location map showing the horizontal projection of the fault plane (divided into 72 square subfaults)and the eight strong-motion stations (triangles)used in this study.This model corresponds to the geometry oftheHarvardCMTsolution(strike=295°,dip=50°).Star shows the hypocenter location of the mainshock.Theepicenterlocation,focal mechanism and depth of the early larger aftershock are also displayed on the map.AsmallmapofMexicowiththelocationoftheearthquakeisshowninthetoprightcorner,a cross-section of thesubductionzoneinthedirectionperpendiculartotheazimuthofthefaultisshowninthetopleftcorner. Figure B 9.1997 Michoacan Earthquake Map showing the source mechanism and a schematic of the fault plane with respect to the Cocos Plate.(Hernandez et al,2001). REVIEW COPY Page B-9 03/10/14 -Z-ALASKA ENERGY AUTHORITY ;AEA11-022SUSITNA-WATANA HYDRO 43-1404-TM-031014 Clean,reliable energy for the next 100 years.CEIl a) c)so 100 180 20 20 300 co)'Diatenoe porpendeutortothetrench4xra) b) Depth Figure 13.Tectonici of the earthquake.(a)Cross section perpendiculartothestrikeshowingscimictyrordedbyCASClnElSulvdortoweca1996and200,and tho fauk planedefinedbythissuudy.The bending of the subd plat is shown by &thick line.(o)Perspectivemapviewoftheslip distributi with the hs y il itoteaieanusofthesubductionnone,The dip ofthe oubdecting plete khercence the location ot themainmomentreleasezone.See color version of Unis figure at back of this issue. Figure B 10.2001 El Salvador Earthquake Cross section showing the preferred source solution of the El Salvador earthquake plotted with the regional seismicity and a line showing the top of the Cocos Plate.The bottom figure is a tectonic interpretation of the earthquake (Vallee et al.,2003). REVIEW COPY Page B-10 03/10/14 -y ALASKA ENERGY AUTHORITY SUSITNA-WATANA HYDRO AEA11-022 13-1404-TM-031014 Clean,reliable energy for the next 100 years.CEIl Distance from Peru-Chile Trench (km) 0 60 100 150 200 250 300 30 400 450 500 0 o LPL ee el.;TT lapoteh beeer LZ A TSR]Chucapaca on ean ProjectSite cto cue ae GEL60tsPeru-Chile baad ee Trench }yep x ;Crepeebed:bd -£oa ae j jebopesa.tot $4 aan - O 150 : ; obs + in oe i .. 200 i wf hegeed bef ded bw 4 -whe fee i }'}4 :i | .spebd fept bended doe meh ys bpd aopebde foepetdeppeebbsrobbPhbPaa]: 250 'i i i fl 1 {fi RS EEC SOURCE ZONE (as definedby |wannan Depthto Slab (top)Nishenko,1985)Assumed Interface Hypocentral Depth =50km Interface Rupture Distance #170km ----Depthto Slab (bottom)Assumed SLAB SOURCE ZONE m Interface Design Event Slab Hypocentral Depth *100 km Slab Rupture Distance =120 km @ Slab Design Event Figure B 11.2005 Tarpaca Earthquake Cross section showing the geometry of the Nazca Plate used in the MWH (2012)hazard report.. Oistance from the rench (km) Figure B 12.2005 Tarpaca Earthquake Cross section showing the geometry of the Nazca plate,the preferred rupture plane of the2005Tarpacaearthquake,aftershocks (dark blue circles),and background seismicity (light blue circles)(Peyrat et al.,2006). REVIEW COPY Page B-11 03/10/14