NGA-East: National Seismic Hazard Mapping Perspective Mark Petersen USGS Golden, CO

New Madrid Ground Motions Tennessee: Lowered building codes Arkansas: Legislative hearing to lower building codes (Have these ground motions occurred historically?, How do they compare to California earthquake ground motions?) Kentucky: Ground motion equations are conservative, uncertainties high, PSHA not valid- mixing temporal Building code community: Can these ground motions occur? Are there physical limits that can be applied? Have we adequately accounted for the distribution of ground motions and truncation levels?

New Hazard Maps

Ratio of new hazard maps with 2002 maps

Figure 9: CEUS 0.2 s SA attenuation relations for M 7 earthquake on Vs m/s site conditions: AB95 AB05 (Atkinson and Boore, 1995, 2005; F96 (Frankel et al., 1996); T97 T02m (Toro, 1997, 2002); C03 (Campbell, 2003); S01 (Somerville 2001); SV02 (Silva et al., 2002); TP05 (Tavakoli And Pezeshk, 2005) From Chris Cramer

Figure 10: CEUS 1 s SA attenuation relations for M 7 earthquake on Vs m/s site conditions: AB95 AB05 (Atkinson and Boore, 1995, 2005; F96 (Frankel et al., 1996); T97 T02m (Toro, 1997, 2002); C03 (Campbell, 2003); S01 (Somerville 2001); SV02 (Silva et al., 2002); TP05 (Tavakoli And Pezeshk, 2005) From Chris Cramer

From Atkinson and Boore (2006; updated 2007) Does this contradict Intensity data from CEUS and WUS Earthquakes?

Differences 1.Geometrical spreading (r -1.3 vs r -1.0 ) 2.Stress drop 3.Site kappa (0.01 vs 0.02)

Amplitudes decay faster than 1/R at R<70 km. This has important implications for ENA ground motion relations. From Gail Atkinson

Average Stress Drop Determinations 570 bars 290 bars 110 bars ≥410 bars From Art Frankel

Some intriguing ground motion information from MMI, based on the USGS “Did You Feel It?” website database. Higher ENA MMI appears to persist to near-source, suggesting higher stress drops Slide and caption from Gail Atkinson From Art Frankel

From Frankel et al. (1990)

Conclusions Need more information on geometric spreading, stress drop, kappa Need to resolve the discrepancy between new attenuation relations and MMI data Need to determine whether high values over New Madrid are reasonable Need to involve CEUS ground motion modelers (Hermann, Chapman, Ebel, others)

Corrected for Atkinson Q model and B-C boundary site amplification Acceleration Spectral Amp. Frequency (Hz) kappa= 0.01 kappa= 0.02 Vs30= 705 m/sec Vs30= 470 m/sec We used kappa=0.01 for CEUS B-C sites

locationdate Mw (From Herrmann) Mblg Depth (km) Corner Frequency (hz) Stress drop (bars) W. KY 6/20/05 12: N.E. AR 5/1/05 12: MO-AR border 10/21/99 8:18 3.7*3.911≥ 8≥410 Fort Payne, AL 4/27/03 8: S.W. Utah 2/23/01 21: S.W. Utah 10/22/99 19: Stress Drop Determinations from Spectral Ratios * Determined from comparison of spectral levels with 5/1/05 event From Art Frankel

USIN Vs30= 705 m/sec OLIL Vs30= 470 m/sec What is kappa (high-frequency spectral falloff) for CEUS B-C sites? Vs30= 760 m/sec

5/1/05 earthquake, NE Arkansas, M4.2, fc= 2 Hz (at OLIL) Corrected for Atkinson Q model and B-C boundary site amplification Acceleration spectral Amp. Frequency (Hz)

USIN OLIL PVMO Mw= 3.6 (Herrmann), fc= 8-12 Hz, stress drop= bars fc= 12 Hz fc= 9 Hz 8 UTMT fc= 8 Hz Western Kentucky 6/20/05 12:21 UTC, d= 21 km Spectral Ratio Frequency (Hz) All spectral ratios wrt Md 2.7 foreshock 8 USIL red: fc= 12 Hz blue: fc= 8 Hz OLIL red: fc= 12 Hz blue: fc= 8 Hz

uncorrected spectra (proportional to velocity 1-10 Hz) 6/20/05 W. Kentucky Station USIN Dist= 167 km From Art Frankel

Brune spectra for earthquakes whose moments differ by factor of 125 and have equal stress drops Ratio of spectrum of larger event divided by spectrum of smaller event fc= 5 Hz fc= 25 Hz fc= 5 Hz fc= 25 Hz Taking spectral ratio of collocated earthquakes removes path and site effects (and instrument response) and provides estimate of corner frequency of large event (and the small event if you have sufficient bandwidth) From Art Frankel

Red stars show earthquakes studied here, Mw Triangles are broadband stations of the New Madrid seismic network and other ANSS stations used in this study From Art Frankel