Hanford Sitewide Probabilistic Seismic Hazard Analysis 2014 Contents 8.0 Seismic Source Characterization .................................................................................................. 8.1 8.1 Building the SSC Model: Overview and Approach ............................................................ 8.1 8.1.1 Criteria for Defining Seismic Sources ....................................................................... 8.1 8.1.2 Data Evaluation Process ............................................................................................ 8.3 8.1.3 Evaluation of Models and Methods ........................................................................... 8.8 8.1.4 Types of Seismic Sources Identified and Characterized in the SSC Model .............. 8.10 8.1.5 Structure of the SSC Model Logic Trees .................................................................. 8.17 8.2 Cascadia Subduction Zone Sources ..................................................................................... 8.23 8.2.1 Approach Using Previous Studies and the Evaluation of New Data ......................... 8.23 8.2.2 Intraslab Source, Including Catalog Analyses........................................................... 8.24 8.2.3 Plate Interface Source ................................................................................................ 8.28 8.3 Seismic Source Zones .......................................................................................................... 8.36 8.3.1 Two Types of Seismic Source Zones ........................................................................ 8.36 8.3.2 Source Zone Characteristics for the SSC Model ....................................................... 8.37 8.3.3 Yakima Fold and Thrust Belt Background Source Zone .......................................... 8.54 8.3.4 Source Zones B, C, and D ......................................................................................... 8.65 8.4 Fault Sources ........................................................................................................................ 8.71 8.4.1 Seismogenic Probability ............................................................................................ 8.74 8.4.2 Approaches to Segmentation and Future Ruptures ................................................... 8.81 8.4.3 Fault Characteristics Included in the SSC Model ..................................................... 8.85 8.5 References ............................................................................................................................ 8.179 8.1 2014 Hanford Sitewide Probabilistic Seismic Hazard Analysis Figures 8.1 Seismic source zones characterized in the SSC model and earthquake epicenters in the Hanford PSHA crustal catalog having E[M] ≥ 1.85 ................................................................ 8.13 8.2 Fault sources included in the SSC model ................................................................................. 8.15 8.3 Logic tree for the Cascadia subduction zone sources, which include the intraslab source zone and the plate interface ...................................................................................................... 8.18 8.4 Logic tree for seismic source zones ......................................................................................... 8.19 8.5 Logic tree for the fault segment geometry and slip rate........................................................... 8.21 8.6 Logic tree for characteristic magnitudes of fault sources. ....................................................... 8.22 8.7 Logic tree for the recurrence characteristics of fault segments. ............................................... 8.22 8.8 Diagrammatic depiction of the seismic sources and other elements related to the CSZ ......... 8.24 8.9 Distribution of seismicity in the area covered by the subduction earthquake catalog ............. 8.26 8.10 Cross section of intraslab seismicity along the line of section shown in panel ....................... 8.27 8.11 Earthquake recurrence curve for the intraslab source .............................................................. 8.28 8.12 Figure from Hyndman (2013) summarizing the landward limits of the fully locked and linear transition zones based on leveling and tide gauge geodetic data ................................... 8.30 8.13 Alternative interpretation of the isotherms on the plate interface based on thermal modeling assuming circulation of fluids within the subducting slab ....................................... 8.31 8.14 Maps from Hyndman (2013) showing the locked and transition zones of the plate interface defined from thermal and geodetic modeling in comparison to the location of ETS events shown in red .......................................................................................................... 8.32 8.15 Map showing the location of ETS events and interpretation of their significance relative to the location of the seismogenic interface ............................................................................. 8.33 8.16 Interpreted location of forearc mantle corner that lies at the intersection of the forearc Moho and the plate interface .................................................................................................... 8.34 8.17 Interpretation of the eastern or downdip extent of the seismogenic plate interface in the BC Hydro study ....................................................................................................................... 8.35 8.18 Map of the four seismic source zones in the SSC model ......................................................... 8.37 8.19 Focal depth distribution for all earthquakes within the YFTB source zone ............................ 8.40 8.20 Focal depth distribution of observed earthquakes M ≥ 2 within the YFTB source zone ......... 8.41 8.21 Examples of distributions of ZTOR, distance to the top of rupture, for two assumed fault dips and seismogenic thicknesses and a range of magnitudes ................................................. 8.43 8.22 Earthquake focal mechanisms in the Hanford Site region ....................................................... 8.44 8.23 Observed and predicted GPS-derived velocities within the YFB relative to North America .................................................................................................................................... 8.45 8.24 Rake angles for earthquake focal mechanisms in the YFB region .......................................... 8.46 8.25 Distribution of strikes from the analysis of earthquake focal mechanisms, shown as a histogram and a rose diagram .................................................................................................. 8.46 8.26 Distribution of fault dips from the analysis of earthquake focal mechanisms, shown as a histogram and a rose diagram .................................................................................................. 8.47 8.2 Hanford Sitewide Probabilistic Seismic Hazard Analysis 2014 8.27 Probability distributions of Mmax for all fault sources in the SSC model. ............................. 8.49 8.28 Seismicity from the crustal earthquake catalog in the vicinity of the YFB. Upper panel indicates the magnitude of earthquakes and shows the spatial clustering of many of the smaller magnitude earlthquakes, such as the Wooded Island swarm near the southeastern boundary of the Hanford site boundary. Magnitude values used in the plots are E[M] values ....................................................................................................................................... 8.52 8.29 Location of the YFTB eastern boundary with Zone C ............................................................. 8.55 8.30 Edge of craton as defined by 87Sr/86Sr = 0.706 isopleth. .......................................................... 8.56 8.31 Location of deep boreholes that penetrated basement rocks in the Hanford study area. ......... 8.56 8.32 Location of Ice Harbor dikes, cross-sectional model of Blakely et al. (2013), and the Darcell-10 well within the Pasco gravity low .......................................................................... 8.57 8.33 Location of southern boundary of YFTB source zone with Zones C and D. ........................... 8.58 8.34 YFTB western boundary encompasses the extent of the fault sources and separates the YFTB source zone from the Cascade tectonic province to the west. ....................................... 8.59 8.35 Focal depth distribution for all earthquakes within the YFTB source zone ............................ 8.60 8.36 YFTB source zone recurrence curves ...................................................................................... 8.62 8.37 Rake angles for earthquake focal mechanisms in the YFB region .......................................... 8.64 8.38 Earthquake recurrence curve for Zone B ................................................................................. 8.67 8.39 Earthquake recurrence curve for Zone C ................................................................................. 8.67 8.40 Earthquake recurrence curve for Zone D ................................................................................. 8.68 8.41 Comparison of recurrence curves for all source zones ............................................................ 8.68 8.42 Seismicity from the project crustal earthquake catalog in the vicinity of the seismic source zones ............................................................................................................................