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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) 4.5 5.0 5.5 6.0 6.5 7.0 7.5 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) 4.5 5.0 5.5 6.0 6.5 7.0 7.5 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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4.5 5.0 5.5 6.0 6.5 7.0 7.5 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 Boston0.550.290.790.601.011.02 New York City.57.32.83.641.011.02 Washington D.C..51.26.77.581.011.02 Pittsburgh.45.21.74.531.011.02 Charleston.59.34.83.671.011.02 Atlanta.49.24.74.561.021.03 Cincinnati.38.18.70.511.011.02 Chicago.37.18.75.521.011.02 Memphis.52.25.78.581.011.02 Baton Rouge.57.31.82.611.011.02 St. Louis.38.19.72.531.011.02 Minneapolis.38.16.74.491.001.01 Wichita.37.18.72.511.01 Austin.49.26.78.581.011.02 Rapid City.37.19.72.511.001.01 Denver.41.25.73.541.001.01 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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Earthquake hazard isn’t a physical thing we measure. It's something mapmakers define and then use computer programs to predict. To decide how much to believe.

Earthquake hazard isn’t a physical thing we measure. It's something mapmakers define and then use computer programs to predict. To decide how much to believe.

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