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EPRI/SOG Mmax –Six earth-science teams, diverse methods largest observed eq (+ increment) catalog statistics – extreme occurrences seismogenic feature: size, crustal setting, etc. extrapolate frequency-magnitude curve (e.g., the 1,000-year eq) global analogs saturation of m b scale others … –Broad distributions reflect diverse methods & large uncertainties –Approximate center: mid-m b -5 (quiet sites), mid-m b -6 (active sites) USGS Mmax –CEUS global analogs: stable continental regions (AJ), Bhuj Craton: M 7.0 Extended Margin: M 7.5 Mmax distribution for 2008 Figure A2-1

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Figure A2-2

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EPRI/SOG and USGS Mmax distributions for South Texas Project site’s host source zones (original EPRI/SOG, not updated for 2006 Gulf of Mexico earthquakes) EPRI/SOG USGS (margin) Figure A2-3 Mmax (m b )

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EPRI/SOG and USGS Mmax distributions for North Anna site’s host source zones USGS (margin) EPRI/SOG Figure A2-4 Mmax (m b )

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Develop alternative Mmax models that span those used in EPRI/SOG (and current PSHA practice) Test Mmax models using USGS hazard model and computer codes –seismicity-based sources only (because they control the mid- to high-frequency hazard at many sites & Mmax is uncertain and controversial) –hold all parameters fixed except Mmax Compare hazard results with current USGS model as ratio hazard maps and lists for selected sites –numerator: alternative Mmax / denominator: standard USGS Mmax –probabilistic ground motions for PGA, 5 Hz, 1 Hz –2% probability of exceedance in 50 years Analysis Figure A2-5

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Alternative Mmax Models M5.0c5.5m –M 5.0 in craton, M 5.5 in margin –m b equivalent: 5.47c, 5.90m (AB95) or 5.27c, 5.67m (J96) M6.0c6.5m –M 6.0 craton, M 6.5 margin –m b equivalent: 6.29c, 6.66m (AB95) or 6.04c, 6.40m (J96) M7.0c7.5m –M 7.0 craton, M 7.5 margin –m b equivalent: 7.00c, 7.32m (AB95) or 6.74c, 7.07m (J96) Figure A2-6

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North Anna m max (m b ) M6.0c6.5mM5.0c5.5mM7.0c7.5m South Texas m max (m b ) M6.0c6.5mM5.0c5.5mM7.0c7.5m Figure A2-7 Mmax (m b )

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Hazard map (PGA, 2% prob of exc in 50 yrs): seismicity sources only, standard USGS Mmax Ratio hazard map (PGA, 2% prob of exc in 50 yrs): seismicity sources only / all sources Warm colors show where seismicity-based sources control hazard. Figure A2-8 (Prob of exc, px: probability of exceedance)

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Alternate Mmax model: M5.0c5.5m Ratio hazard maps (2% prob of exc in 50 yrs) M5.0c5.5m (sso) / standard USGS Mmax model (sso) 0.2-sec SA 1.0-sec SA Figure A2-9 (Prob of exc, px: probability of exceedance)

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Alternate Mmax model: M6.0c6.5m Ratio hazard maps (2% prob of exc in 50 yrs) M6.0c6.5m (sso) / standard USGS Mmax model (sso) 0.2-sec SA 1.0-sec SA Figure A2-10 (Prob of exc, px: probability of exceedance)

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Alternate Mmax model: M7.0c7.5m Ratio hazard maps (2% prob of exc in 50 yrs) M7.0c7.5m (sso) / standard USGS Mmax model (sso) 0.2-sec SA 1.0-sec SA Figure A2-11 (Prob of exc, px: probability of exceedance)

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M5.0c5.5mM6.0c6.5mM7.0c7.5m 0.2 sec1.0 sec0.2 sec1.0 sec0.2 sec1.0 sec Boston New York City Washington D.C Pittsburgh Charleston Atlanta Cincinnati Chicago Memphis Baton Rouge St. Louis Minneapolis Wichita Austin Rapid City Denver Ratios of probabilistic ground motions (2% probability of exceedance in 50 yrs): Alternate Mmax (seismicity sources only) / USGS (seismicity sources only) Figure A2-12

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Alternate Mmax model: M5.0c5.5m Ratio hazard maps (2% prob of exc in 50 yrs) Use M5.0c5.5m for numerator seismicity sources, but add the faults to both the numerator and denominator models 0.2-sec SA 1.0-sec SA Figure A2-13 (Prob of exc, px: probability of exceedance)

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