HR: 08:00h
AN: S21C-01    [Abstracts]
TI: Stress Field around the Locked Portions on the Plate Interface: Result of a Finite Element Simulation and Its Comparison with Seismicity in the Tokai Region, Central Japan
AU: * Nishimura, S
EM: yeti@bosai.go.jp
AF: National Research Institute for Earth Science and Disaster Prevention, 3-1 Tennodai, Tsukuba, Iba 305-0006 Japan
AU: Matsumura, S
EM: shozo@bosai.go.jp
AF: National Research Institute for Earth Science and Disaster Prevention, 3-1 Tennodai, Tsukuba, Iba 305-0006 Japan
AB: Our objective is to know the state of locking in the Tokai region, central Japan on the basis to the seismicity around the plate interface. That is important not only in earth science but also for the mitigation for the forthcoming large interplate earthquake. In order to do this, we need more understanding for deviatoric stress field caused by the locking on the plate interface. In this study, we carry out a numerical simulation using a three-dimensional finite element method with various patterns of locked portion on a simplified plate interface. Through this simulation, we confirm that the interplate coupling brings a significant affection on the stress field. And we can extract some characteristic features of deviatoric stress pattern around the locked portion: (1) Increase of compression in the trenchward side of the foot wall and in the landward side of the hanging wall. (2) Increase of tension in the trenchward side of the hanging wall and in the landward side of the foot wall. (3) Stress concentration both to the upper and lower edges of the locked portion. (4) Significant change in stress direction around the locked portion. The actual seismicity in the Tokai region has a great agreement with the results of our simulated stress field: (1) High seismicity in the trenchward side of the foot wall and in the landward side of the hanging wall. (2) Low or almost inactive seismicity in the trenchward side of the hanging wall and in the landward side of the foot wall. (3) Recognizable change in the directions of P and T axes near the plate interface. This fact may suggest that the deviatoric stress due to the locked portion on the plate interface is enough significant to have its level almost equal to the stress level in the surrounding region. We find through a comparison between the simulated stress field and the actual seismicity that the locked portion in the Tokai region is mainly distribute from 15 km to 25 km depth. Three locked asperities can be recognized in the west of Suruga Bay.
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
DE: 7240 Subduction zones (1207, 1219, 1240)
DE: 7290 Computational seismology
DE: 8123 Dynamics: seismotectonics
DE: 8168 Stresses: general
SC: Seismology [S]
MN: Fall Meeting 2005