HR: 0800h
AN: S31B-0450    [Abstracts]
TI: CyberShake 2007: Update on Physics-Based Probabilistic Seismic Hazard Calculations for Southern California
AU: * Graves, R
EM: robert_graves@urscorp.com
AF: URS Corporation, 566 El Dorado St., 2nd Floor, Pasadena, CA 91101, United States
AU: Callaghan, S
AF: Department of Earth Sciences, University of Southern California, Los Angeles, CA 90089, United States
AU: Deelman, E
AF: Information Sciences Institute, University of Southern California, Los Angeles, CA 90089, United States
AU: Field, E
AF: US Geological Survey, 525 S. Wilson Ave., Pasadena, CA 91125, United States
AU: Gupta, N
AF: Department of Earth Sciences, University of Southern California, Los Angeles, CA 90089, United States
AU: Jordan, T
AF: Department of Earth Sciences, University of Southern California, Los Angeles, CA 90089, United States
AU: Juve, G
AF: Department of Earth Sciences, University of Southern California, Los Angeles, CA 90089, United States
AU: Kesselman, C
AF: Information Sciences Institute, University of Southern California, Los Angeles, CA 90089, United States
AU: Maechling, P
AF: Department of Earth Sciences, University of Southern California, Los Angeles, CA 90089, United States
AU: Mehta, G
AF: Department of Earth Sciences, University of Southern California, Los Angeles, CA 90089, United States
AU: Meyers, D
AF: Department of Earth Sciences, University of Southern California, Los Angeles, CA 90089, United States
AU: Okaya, D
AF: Department of Earth Sciences, University of Southern California, Los Angeles, CA 90089, United States
AU: Vahi, K
AF: Department of Earth Sciences, University of Southern California, Los Angeles, CA 90089, United States
AB: To calculate a physics-based probabilistic hazard curve for a site of interest, we begin with the NSHMP-2002 ERF and identify all ruptures within 200 km of the site of interest. We convert the NSHMP-2002 rupture definition into multiple rupture variations with differing hypocenter location and slip distribution, which results in about 200,000 rupture variations per site. Strain Green Tensors are calculated for the site using the SCEC CVM (v4.0), and then, using reciprocity, we calculate synthetic seismograms for each rupture variation. Peak intensity measures are then extracted from these synthetics and combined with the original rupture probabilities to produce probabilistic seismic hazard curves for the site. Recent improvements include (1) development of a parallel CVM mesh generator, (2) implementation of an efficient 3D visco-elastic finite difference algorithm, (3) efficient storage and retrieval of SGTs, (4) implementation of an efficient earthquake simulation code, and (5) development of an optimized and efficient workflow system. Thus far, we have produced hazard curves for spectral acceleration at a suite of periods ranging from 3 to 10 seconds at about 10 sites in the Los Angeles region. Our preliminary analysis suggests the increased ground motion levels generated in the CyberShake simulations result from rupture directivity and basin response effects. More importantly, we find that the physics-based hazard estimates are much more sensitive to the assumed magnitude-area relation used in the definition of the ruptures than is found in the empirical approach. Our results suggest that a magnitude-area relation based on waveform modeling studies (e.g., Somerville et al, 2006) is the most appropriate parameterization for physics-based hazard calculations. These types of sensitivity analyses will be used to guide the future activities of the CyberShake program.
DE: 7212 Earthquake ground motions and engineering seismology
DE: 7290 Computational seismology
SC: Seismology [S]
MN: 2007 Fall Meeting