HR: 1340h
AN: S23B-0253    [Abstracts]
TI: Deep-Seated Structure of the Median Tectonic Line in the Iyo-nada Sea, Southwest Japan
AU: * Ikeda, M
EM: m-ikeda@ssken.co.jp
AF: Shikoku Research Institute Inc., 2109-8 Yashimanishi-machi, Takamatsu, 761-0192 Japan
AU: Takahashi, T
EM: takahashi13528@yonden.co.jp
AF: Shikoku Electric Power Co. Inc., 2-5 Marunouchi, Takamatsu, 760-8573 Japan
AU: Ohno, Y
EM: oono11374@yonden.co.jp
AF: Shikoku Electric Power Co. Inc., 2-5 Marunouchi, Takamatsu, 760-8573 Japan
AU: Nishizaka, N
EM: nishizaka14981@yonden.co.jp
AF: Shikoku Electric Power Co. Inc., 2-5 Marunouchi, Takamatsu, 760-8573 Japan
AU: Kobayashi, S
EM: s-kobayashi@ssken.co.jp
AF: Shikoku Research Institute Inc., 2109-8 Yashimanishi-machi, Takamatsu, 761-0192 Japan
AU: Kobayashi, S
EM: s-kobayashi@ssken.co.jp
AF: Shikoku Electric Power Co. Inc., 2-5 Marunouchi, Takamatsu, 760-8573 Japan
AU: Hasegawa, T
EM: hasegawa@sogo-ge.co.jp
AF: Sogo Geophysical Exploration Co., Ltd., 1-8-20 Kitashinagawa, Shinagawa-ku, Tokyo, 140-0001 Japan
AU: Hatakeyama, K
EM: hatakeyama@sogo-ge.co.jp
AF: Sogo Geophysical Exploration Co., Ltd., 1-8-20 Kitashinagawa, Shinagawa-ku, Tokyo, 140-0001 Japan
AU: Hasegawa, S
EM: hasegawa@eng.kagawa-u.ac.jp
AF: Kagawa University, 2217-20 Hayashi-cho, Takamatsu, 761-0396 Japan
AU: Matsushima, M
EM: matusima@eng.kagawa-u.ac.jp
AF: Kagawa University, 2217-20 Hayashi-cho, Takamatsu, 761-0396 Japan
AB: Since the 1995 Hyogo-ken Nanbu earthquake, the importance of estimating strong seismic motion near a fault has been more keenly recognized. Therefore, some evaluating methods of strong seismic motion have been proposed and improved in a decade. To assume a precise fault model is one of the most essential factor in the process of evaluating strong seismic motion. We need the precise 3-D fault geometry and fault activity data in assuming the fault model. However, deep structural data of many faults is clarified less than surface geometry data of fault. In this study, we conducted the multi-channel seismic reflection survey for the Median Tectonic Line active fault system (hereafter MTLAFS) in consideration of this point. The MTLAFS is one of the representative active fault systems in Japan (Tsutsumi, 1991; Tsutsumi and Okada, 1996). The MTLAFS in Shikoku is a typical right-lateral strike-slip fault system with length of about 200 km related to the arc-parallel oblique subuduction of the Philippine Sea Plate. The MTLAFS is reactivation fault of the material boundary MTL (Ito et al., 1996), which is terrane boundary of the Sanbagawa belt and the Ryouke belt. Now, the surface geometry of the MTLAFS is very precisely clarified based on geological and geomorphological researches. However, few researches for deep-seated structure of the MTLAFS are conducted, is clarified less than surface fault trace. The aim of this survey is to clarify the deep-seated structure of the MTLAFS distributing in the Iyo-nada Sea of eastern Shikoku in Japan. This survey result indicated that the material boundary MTL with north dipping exists beneath the study area. The MTLAFS on surface may converge with the material boundary MTL in depth of about 2 - 3 km. This fault structure agrees with previous research results in eastern Shikoku (Ito et al., 1996), and also in other areas besides Shikoku where are the Beppu Bay area (Yusa et a., 1992) and the western area of the Kii Peninsula (Yoshikawa et al., 1992). In general, it is clarified from seismic distribution data that many major strike-slip faults (eg. San Andreas Fault system) are high-angle or vertical fault. The MTLAFS with low-angle strike-slip, therefore, shows the faulting mechanism differing from these typical long strike-slip faults with high-angle or vertical strike-slip.
DE: 7221 Paleoseismology (8036)
SC: Seismology [S]
MN: Fall Meeting 2005