EPRISOG Mmax

1
Figure A2-1

• 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 mb scale
• others
• Broad distributions reflect diverse methods
  large uncertainties
• Approximate center mid-mb-5 (quiet sites),
  mid-mb-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

2
Figure A2-2
3
Figure A2-3
Mmax (mb)
EPRI/SOG and USGS Mmax distributions for South
Texas Project sites host source zones (original
EPRI/SOG, not updated for 2006 Gulf of Mexico
earthquakes)
4
Figure A2-4
Mmax (mb)
EPRI/SOG and USGS Mmax distributions for North
Anna sites host source zones
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Figure A2-5
Analysis

• 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

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Alternative Mmax Models
Figure A2-6

• M5.0c5.5m
• M 5.0 in craton, M 5.5 in margin
• mb equivalent 5.47c, 5.90m (AB95) or 5.27c,
  5.67m (J96)
• M6.0c6.5m
• M 6.0 craton, M 6.5 margin
• mb equivalent 6.29c, 6.66m (AB95) or 6.04c,
  6.40m (J96)
• M7.0c7.5m
• M 7.0 craton, M 7.5 margin
• mb equivalent 7.00c, 7.32m (AB95) or 6.74c,
  7.07m (J96)

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Figure A2-7
4.5 5.0
5.5 6.0 6.5
7.0 7.5
Mmax (mb)
4.5 5.0
5.5 6.0 6.5
7.0 7.5
Mmax (mb)
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Figure A2-8
Hazard map (PGA, 2 prob of exc in 50
yrs) seismicity sources only, standard USGS Mmax
(Prob of exc, px probability of exceedance)
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.
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Figure A2-9
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)
(Prob of exc, px probability of exceedance)
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Figure A2-10
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)
(Prob of exc, px probability of exceedance)
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Figure A2-11
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)
(Prob of exc, px probability of exceedance)
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Figure A2-12
Ratios of probabilistic ground motions (2
probability of exceedance in 50 yrs) Alternate
Mmax (seismicity sources only) / USGS (seismicity
sources only)
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Figure A2-13
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
(Prob of exc, px probability of exceedance)