HR: 0800h
AN: S41A-0956    [Abstracts]
TI: Multi-parameter Dynamic Rupture Inversion of the Western Tottori Earthquake, Japan
AU: * Corish, S M
EM: scorish@umail.ucsb.edu
AF: Earth and Environmental Sciences Division, Los Alamos National Laboratory, P.O. Box 1663, Los Alamos, NM 87545 United States
AU: Bradley, C R
EM: 505-665-3687
AF: Earth and Environmental Sciences Division, Los Alamos National Laboratory, P.O. Box 1663, Los Alamos, NM 87545 United States
AU: Olsen, K B
EM: kbolsen@sciences.sdsu.edu
AF: Institute for Crustal Studies, University of California, Santa Barbara, 1140 Girvetz Hall, Santa Barbara, CA 93106 United States
AB: We have used a non-linear, dynamic inversion process developed by Peyrat and Olsen (2004) to test the possibility of making simultaneous estimates of stress drop and slip-weakening distance on a fault. The forward problem is solved for spontaneous rupture using a three-dimensional, fourth-order staggered-grid finite difference method. The resulting computed seismograms are compared with observed seismic data, and a neighborhood algorithm is used to invert for the initial conditions that yield the lowest misfits. Here we apply the method to the magnitude 6.6 Western Tottori, Japan earthquake of October 2000. Data from 12 strong motion stations, bandpass filtered between 0.05 Hz and 0.5 Hz, are used to calibrate the misfit of the computed models. We discretize the fault surface into 18 regions and invert for stress drop and slip-weakening distance in each region simultaneously. The stress drop and slip-weakening distance are constrained to -2 to 5 MPa and 10 to 130 cm, respectively. We find that the best-fit initial stress models are similar, regardless of friction, and that slip-weakening distances of 10 cm to 60 cm are preferred over higher values. These results are in agreement with the single-parameter inversions done by Peyrat and Olsen (2004) and with an estimated slip-weakening distance of 28 cm determined independently from strong motion data for the Western Tottori earthquake. The results show some promise that low-frequency seismic data may be used to estimate stress drop and friction parameters independently for large earthquakes.
DE: 7260 Theory and modeling
DE: 8123 Dynamics, seismotectonics
DE: 7209 Earthquake dynamics and mechanics
DE: 3210 Modeling
DE: 3230 Numerical solutions
SC: Seismology [S]
MN: 2004 AGU Fall Meeting