HR: 10:35h
AN: S21G-02    [PDF]
TI: Dynamic Rupture Processes on Fault Models under Stress Fields Estimated from Active Fault Information: The 1995 Kobe, Japan, Earthquake
AU: * Kase, Y
EM: kasep@ni.aist.go.jp
AF: Active Fault Research Center, GSJ/AIST, AIST Tsukuba Central 7, Tsukuba, 305-8567 Japan
AU: Sekiguchi, H
EM: haruko.sekiguchi@aist.go.jp
AF: Active Fault Research Center, GSJ/AIST, AIST Tsukuba Central 7, Tsukuba, 305-8567 Japan
AU: Sugiyama, Y
EM: sugiyama-y@aist.go.jp
AF: Active Fault Research Center, GSJ/AIST, AIST Tsukuba Central 7, Tsukuba, 305-8567 Japan
AU: Horikawa, H
EM: h.horikawa@aist.go.jp
AF: Active Fault Research Center, GSJ/AIST, AIST Tsukuba Central 7, Tsukuba, 305-8567 Japan
AU: Ishiyama, T
EM: t-ishiyama@aist.go.jp
AF: Active Fault Research Center, GSJ/AIST, AIST Tsukuba Central 7, Tsukuba, 305-8567 Japan
AU: Satake, K
EM: kenji.satake@aist.go.jp
AF: Active Fault Research Center, GSJ/AIST, AIST Tsukuba Central 7, Tsukuba, 305-8567 Japan
AB: We tested our 3-D finite-difference dynamic rupture model by comparing the rupture process of the 1995 Kobe earthquake estimated from waveform inversions. In our model, the stress fields are estimated from geomorphological and geological studies of active faults. Surface rupture of the Kobe earthquake appeared only on the fault southwest of the rupture initiation (Hokudan segment). The waveform inversion results indicate that large moment releases occurred in the entire Hokudan segment and deep part of the Rokko-san segment, northeast of the epicenter. We tested many fault models, by varying the location of discontinuity, because the geometry of the segment boundary is located beneath Akashi strait and not well known. In our 3-D finite-difference model, we modeled the variation of fault strike and dip angles by introducing heterogeneity of the initial stress field. We assumed hydrostatic condition, and also assumed several patterns of stress drop distribution along the fault dip (in the depth direction). We used observed surface slip, both horizontal and vertical, as the constraints of model. When the two segments are discontinuous and stress drop is zero in the top 8 km of the Rokko-san segment, our dynamic modeling produces rupture area similar to the Kobe earthquake. The rupture propagates smoothly on the Hokudan segment. The rupture on the Rokko-san segment, however, is delayed for 8 seconds, which is inconsistent with the waveform inversion results. In order to rupture the Rokko-san segment first, the two segments must be continuous or the Rokko-san segment must have some discontinuous subfaults. In such cases, however, surface slip is 0.5 m or larger on the Rokko-san segment regardless of the stress drop distribution, hence, the surface ruptures are expected to appear. We need to consider more heterogeneous stress drop distribution to reproduce the observed rupture process.
DE: 7209 Earthquake dynamics and mechanics
DE: 7221 Paleoseismology
DE: 7260 Theory and modeling
DE: 8010 Fractures and faults
DE: 8164 Stresses--crust and lithosphere
SC: Seismology [S]
MN: 2003 Fall Meeting