• 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

Figure A2-1

Figure A2-2

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)

South Texas Project

4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0

mmax (mb)

Fre

que

ncy

4.5 5.0 5.5 6.0 6.5 7.0 7.5

EPRI/SOG

USGS(margin)

Figure A2-3

Mmax (mb)

EPRI/SOG and USGS Mmax distributions for North Anna site’s host source zones

North Anna

4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0

mmax (mb)

Fre

quency

USGS(margin)

4.5 5.0 5.5 6.0 6.5 7.0 7.5

EPRI/SOG

Figure A2-4

Mmax (mb)

• 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

Alternative Mmax Models

• 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)

Figure A2-6

4.5 5.0 5.5 6.0 6.5 7.0 7.5

4.5 5.0 5.5 6.0 6.5 7.0 7.5

North Anna

mmax (mb)

M6.0c6.5mM5.0c5.5m M7.0c7.5m

SouthTexas

mmax (mb)

M6.0c6.5mM5.0c5.5m M7.0c7.5m

Figure A2-7

Mmax (mb)

Mmax (mb)

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)

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)

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)

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)

M5.0c5.5m M6.0c6.5m M7.0c7.5m

0.2 sec 1.0 sec 0.2 sec 1.0 sec 0.2 sec 1.0 sec

Boston 0.55 0.29 0.79 0.60 1.01 1.02

New York City .57 .32 .83 .64 1.01 1.02

Washington D.C. .51 .26 .77 .58 1.01 1.02

Pittsburgh .45 .21 .74 .53 1.01 1.02

Charleston .59 .34 .83 .67 1.01 1.02

Atlanta .49 .24 .74 .56 1.02 1.03

Cincinnati .38 .18 .70 .51 1.01 1.02

Chicago .37 .18 .75 .52 1.01 1.02

Memphis .52 .25 .78 .58 1.01 1.02

Baton Rouge .57 .31 .82 .61 1.01 1.02

St. Louis .38 .19 .72 .53 1.01 1.02

Minneapolis .38 .16 .74 .49 1.00 1.01

Wichita .37 .18 .72 .51 1.01 1.01

Austin .49 .26 .78 .58 1.01 1.02

Rapid City .37 .19 .72 .51 1.00 1.01

Denver .41 .25 .73 .54 1.00 1.01

Ratios of probabilistic ground motions (2% probability of exceedance in 50 yrs):

Alternate Mmax (seismicity sources only) / USGS (seismicity sources only)

Figure A2-12

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)