HR: 10:50h
AN: S52A-03    [Abstracts]
TI: TeraShake: Strong Shaking in Los Angeles Expected From Southern San Andreas Earthquake
AU: * Olsen, K
EM: kbolsen@sciences.sdsu.edu
AF: San Diego State University, 5500 Campanile Dr, San Diego, CA 92182 United States
AU: Day, S
EM: day@moho.sdsu.edu
AF: San Diego State University, 5500 Campanile Dr, San Diego, CA 92182 United States
AU: Minster, J
EM: jbminster@ucsd.edu
AF: Scripps Institution of Oceanography, University of California at San Diego, 9500 Gilman Dr, La Jolla, CA 92093 United States
AU: Cui, Y
EM: yfcui@sdsc.edu
AF: San Diego Super Computer Center, University of California at San Diego, 9500 Gilman Dr, La Jolla, CA 92093 United States
AU: Chourasia, A
EM: amit@sdsc.edu
AF: San Diego Super Computer Center, University of California at San Diego, 9500 Gilman Dr, La Jolla, CA 92093 United States
AU: Faerman, M
EM: mfaerman@sdsc.edu
AF: San Diego Super Computer Center, University of California at San Diego, 9500 Gilman Dr, La Jolla, CA 92093 United States
AU: Moore, R
EM: moore@sdsc.edu
AF: San Diego Super Computer Center, University of California at San Diego, 9500 Gilman Dr, La Jolla, CA 92093 United States
AU: Hu, Y
EM: yhu@sdsc.edu
AF: San Diego Super Computer Center, University of California at San Diego, 9500 Gilman Dr, La Jolla, CA 92093 United States
AU: Zhu, J
EM: jzhu@sdsc.edu
AF: San Diego Super Computer Center, University of California at San Diego, 9500 Gilman Dr, La Jolla, CA 92093 United States
AU: Li, Y
EM: yili@sdsc.edu
AF: San Diego Super Computer Center, University of California at San Diego, 9500 Gilman Dr, La Jolla, CA 92093 United States
AU: Maechling, P
EM: maechlin@usc.edu
AF: Department of Earth Sciences, University of Southern California, Los Angeles, CA 90089 United States
AU: Jordan, T
EM: tjordan@usc.edu
AF: Department of Earth Sciences, University of Southern California, Los Angeles, CA 90089 United States
AB: We have carried out some of the largest and most detailed earthquake simulations completed to date (TeraShake), in which we model ground motions expected from a large earthquake on the southern San Andreas fault. The TeraShake calculations simulate 4 minutes of 0-0.5 Hz ground motion in a 180,000 km² area of southern California, for a M 7.7 earthquake along the 199 km section of the San Andreas fault between Cajon Creek north of Los Angeles, and Bombay Beach on the shore of the Salton Sea. The two segments of the San Andreas fault south of the 1857 rupture, the San Bernardino Mountains segment and the Coachella Valley segment, have not seen a major event since 1812 and about 1690, respectively. The average recurrence interval for large earthquakes with surface rupture on these segments are only 146+91-60 yrs and 220±13 yrs, respectively. An inescapable conclusion is that a major component of the seismic hazard in southern California and northern Mexico stems from a putative large earthquake on this part of the San Andreas Fault. The simulations include ruptures propagating both northwest-ward and southeast-ward on the fault. The kinematic source model is based on that inferred for the 2002 Denali Earthquake. The crustal model is taken from the SCEC 3D Community Velocity Model Version 3.0 discretized into 200 m³ cubes. The results show that the chain of sedimentary basins between San Bernardino and downtown Los Angeles form an effective waveguide that channels Love waves along the southern edge of the San Bernardino and San Gabriel Mountains. Earthquake scenarios in which the guided wave is efficiently excited (scenarios with northward rupture) produce unusually high long-period ground motions over much of the greater Los Angeles region. Intense, localized amplitude modulations arising from variations in waveguide cross-section can be explained to a remarkable level of accuracy in terms of energy conservation for the guided mode. Less certain are the predicted absolute amplitudes of the ground motion extremes, as nonlinearity induced by the higher-than-anticipated waveguide amplifications we have identified here would likely cause significant reduction of both shear modulus and Q factor in the near-surface layers. The simulations using a parallel fourth-order finite-difference code required up to 19,000 CPU hours on 240 processors of the 10 teraflops IBM Power4+ DataStar supercomputer at San Diego Supercomputer Center. Animations of the simulated wave propagation and synthetic seismograms from TeraShake are available at http://www.scec.org/TeraShake.
UR: http://www.scec.org/TeraShake
DE: 0545 Modeling (4255)
DE: 0560 Numerical solutions (4255)
DE: 7212 Earthquake ground motions and engineering seismology
DE: 7290 Computational seismology
SC: Seismology [S]
MN: Fall Meeting 2005