HR: 17:30h
AN: S42H-07    [PDF]
TI: Rupture Process Inversion Using 3-D Green's Functions: The 1995 Kobe Earthquake Revisited
AU: * Koketsu, K
EM: koketsu@eri.u-tokyo.ac.jp
AF: Earthquake Research Institute, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-0032 Japan
AU: Ohno, T
EM: ohno@feg.co.jp
AF: Faculty of Science, Ibaraki Univ., 2-1-1 Bunkyo, Mito, 310-8512 Japan
AU: Ikegami, Y
EM: y-ikegami@crc.co.jp
AF: CRC Solutions Corp., 2-7-5 Minamisuna, Koto-ku, Tokyo, 136-8581 Japan
AB: In order to reliably simulate and predict strong ground motions, we need accurate models of the earthquake source and rupture process. The models are usually determined by inversion of strong motion, teleseismic or geodetic data, and the choice of Green's functions (GFs) greatly influences the inversion results (Graves and Wald; Wald and Graves, 2001). In particular, this problem should be critical for situations such as the 1995 Kobe earthquake where strong velocity variations are known to exist, but all the previous studies (e.g., Yoshida et al., 1996) used only 1-D (horizontally layered or halfspace) GFs. The GFs in this study are calculated for strong motion and geodetic data from the 1995 Kobe earthquake using a 3-D crustal structure with surface topography (Afnimar et al., 2002) and the voxel FEM code (Koketsu et al., 2003). The comparison of the 3-D GFs to the 1-D ones used in Yoshida et al. (1996) shows that the strong motion GFs are greatly deformed by the 3-D structure. The Green's seismograms at stations in the Osaka basin have surface wave codas with large amplitudes and long duration, and the basin sediments delayed the arrival of the S wave train. However, the geodetic GFs are not changed so much by the crustal structure, though some amplification can be found in horizontal displacements at the basin stations. The results of inversions reflect this difference in sensitivity. The slip distribution recovered by a strong motion inversion with the 3-D GFs is significantly different from the result of Yoshida et al. (1996). The most distinct feature in the 3-D strong motion result is that the asperity under the downtown of Kobe is more intensified than the asperity close to the rupture initiation. The slips under the Awaji island are now concentrated in a shallow part along the Nojima fault as in the other studies. On the other hand, the 3-D geodetic result is not so different from the counterpart in Yoshida et al. (1996), except that the slips in the asperities become a little larger. We will also compare our 3-D results with those by inversion with a hybrid set of 1-D rock and soil GFs (Sekiguchi et al., 1996; Wald, 1996).
DE: 7203 Body wave propagation
DE: 7209 Earthquake dynamics and mechanics
DE: 7212 Earthquake ground motions and engineering
DE: 7260 Theory and modeling
SC: Seismology [S]
MN: 2003 Fall Meeting