HR: 0800h
AN: S31B-0443    [Abstracts]
TI: Effects of Long-Period Ground Motion in Distant Basins: The 1906 San Francisco Earthquake and Comparison with Japanese Cases
AU: * Ikegami, Y
EM: ikegami@eri.u-tokyo.ac.jp
AF: Earthquake Research Institute,University of Tokyo, 1-1-1, Yayoi, Bunkyo-ku, Tokyo, Tokyo, 113-0032, Japan
AU: * Ikegami, Y
EM: ikegami@eri.u-tokyo.ac.jp
AF: ITOCHU Techno-Solutions Corporation, 2-5, Kasumigaseki 3-chome, Chiyoda-ku, Tokyo, 100-6080, Japan
AU: Koketsu, K
EM: koketsu@eri.u-tokyo.ac.jp
AF: Earthquake Research Institute,University of Tokyo, 1-1-1, Yayoi, Bunkyo-ku, Tokyo, Tokyo, 113-0032, Japan
AU: Kimura, T
EM: tkimura@eri.u-tokyo.ac.jp
AF: Earthquake Research Institute,University of Tokyo, 1-1-1, Yayoi, Bunkyo-ku, Tokyo, Tokyo, 113-0032, Japan
AU: Miyake, H
EM: hiroe@eri.u-tokyo.ac.jp
AF: Earthquake Research Institute,University of Tokyo, 1-1-1, Yayoi, Bunkyo-ku, Tokyo, Tokyo, 113-0032, Japan
AB: Large earthquakes at shallow depths often excite long-period ground motions in distant sedimentary basins and damage large-scale structures. We have reported these effects with simulations of the 2003 Tokachi-oki and 2004 off-Kii peninsula, Japan, earthquakes using finite element method (FEM) of a voxel mesh. Besides of the above, we have performed long-period ground motion simulation for the 1906 San Francisco earthquake using the source model of Wald et al.(1993). Our simulation excited long-period ground motions in the LA basin in at a period of 7 sec. However, the results are not so strong as compared with the velocity response at distant basins during the above Japanese subduction-zone earthquakes. One of the reasons might be that the rupture directivity effect is not so strong for the southern region including the LA basin, because the large asperities of the 1906 San Francisco earthquake are mainly located at the northern region of the hypocenter. To clarify the quantitative response in the LA basin for the 1906 event, we will compare simulation results using other source models of Thatcher et al. (1997) and Song et al. (2007) that consist of larger asperities at the source region than the Wald's source model. Regarding the long-period ground motion simulation, our FEM code has advantage to deal with the effect of sea and topography, and the effect of intrinsic factor with the Rayleigh damping. We showed strong excitation of long- period ground motion with a period 7.4 sec in the Yufutsu basin during the 2003 Tokachi-Oki earthquake. Comparison of the simulated waveforms between with/without sea model has confirmed the significant contribution of long-period ground motion from the sea side of the Yufutsu basin. The intrinsic attenuation (Qp and Qs) is important parameter governing the wave propagation in a long distance. We have introduced it with the Rayleigh damping in the FEM code that can fit the Q value at two different frequency points in order to suit broader frequency range for the constant Q model. Toward realistic ground motion simulation, we will examine the above two effects on the long-period components reproduced by the 1906 San Francisco earthquake.
DE: 0560 Numerical solutions (4255)
DE: 3285 Wave propagation (0689, 2487, 4275, 4455, 6934)
DE: 5144 Wave attenuation
DE: 7255 Surface waves and free oscillations
DE: 7290 Computational seismology
SC: Seismology [S]
MN: 2007 Fall Meeting