HR: 1330h
AN: T52B-0263    [PDF]
TI: Combined wide-angle and multichannel seismic survey at an asperity of subduction earthquakes in the Japan Trench
AU: * Kodaira, S
EM: kodaira@jamstec.go.jp
AF: Japan Marine Science and Technology Center, 3173-25 Showa-machi Kanazawa-ku, Yokohama, 236-0001 Japan
AU: Miura, S
EM: miuras@jamstec.go.jp
AF: Japan Marine Science and Technology Center, 3173-25 Showa-machi Kanazawa-ku, Yokohama, 236-0001 Japan
AU: Smith, A J
EM: asmith@jamstec.go.jp
AF: Japan Marine Science and Technology Center, 3173-25 Showa-machi Kanazawa-ku, Yokohama, 236-0001 Japan
AU: Sato, T
EM: tsato@jamstec.go.jp
AF: Japan Marine Science and Technology Center, 3173-25 Showa-machi Kanazawa-ku, Yokohama, 236-0001 Japan
AU: Tsuru, T
EM: tsurut@jamstec.go.jp
AF: Japan Marine Science and Technology Center, 3173-25 Showa-machi Kanazawa-ku, Yokohama, 236-0001 Japan
AU: Fujie, G
EM: fujie@jamstec.go.jp
AF: Japan Marine Science and Technology Center, 3173-25 Showa-machi Kanazawa-ku, Yokohama, 236-0001 Japan
AU: Ito, A
EM: iaki@jamstec.go.jp
AF: Japan Marine Science and Technology Center, 3173-25 Showa-machi Kanazawa-ku, Yokohama, 236-0001 Japan
AU: Takahashi, N
EM: narumi@jamstec.go.jp
AF: Japan Marine Science and Technology Center, 3173-25 Showa-machi Kanazawa-ku, Yokohama, 236-0001 Japan
AU: Suyehiro, K
EM: suyehiro@jamstec.go.jp
AF: Japan Marine Science and Technology Center, 3173-25 Showa-machi Kanazawa-ku, Yokohama, 236-0001 Japan
AU: Kaneda, Y
EM: kaneday@jamstec.go.jp
AF: Japan Marine Science and Technology Center, 3173-25 Showa-machi Kanazawa-ku, Yokohama, 236-0001 Japan
AU: Hino, R
EM: hino@aob.geophys.tohoku.ac.jp
AF: University of Tohoku, Aoba Aramaki Aoba-ku, Sendai, 980-8578 Japan
AU: Mochizuki, K
EM: kimi@eri.u-tokyo.ac.jp
AF: University of Tokyo, Yayoi 1-1-1 Bunkyo-ku, Tokyo, 113-0032 Japan
AU: Kasahara, J
EM: kasa2@eri.u-tokyo.ac.jp
AF: University of Tokyo, Yayoi 1-1-1 Bunkyo-ku, Tokyo, 113-0032 Japan
AU: Kanazawa, T
EM: kanazawa@eri.u-tokyo.ac.jp
AF: University of Tokyo, Yayoi 1-1-1 Bunkyo-ku, Tokyo, 113-0032 Japan
AB: Recent progress of seismic wave form inversion revealed overlapping asperities of large earthquakes in the Japan Trench, e.g., the 1994 Sanriku-Haruka-Oki earthquake (M=7.5) and 1968 Tokachi-Oki earthquake (M=7.9). It is also recognized that the epicenters (initial break) of both earthquakes are situated at the trench-ward edge of the asperities, and the aftershocks were observed only around the asperities. Investigating structural factor controlling these asperity and seismicity pattern is believed to provide important and fundamental information to the physics of earthquakes. In August, 2003, we acquired wide-angle and multichannel seismic data covering the entire asperity region. The purpose of this study is to image structures of the asperity, and investigate the structures affecting the distribution of the seismicity pattern. Part of MCS data was processed onboard. We made CDP stacks by applying multiple suppression and poststack time migration. From the migration section of the dip profile, we recognized several key structures related to a subduction process; e.g., 1) the top of subducted oceanic crust can be traced up to 80 km from the trench axis. This reflector is recognized at 10 s twt to 70 km from the axis, rising up to 9s at 75 km then again down to 10 s farther than 75 km, 2) from 30 to 50km and 70 to 75 km, a weak reflector which is parallel to the top of the oceanic crust is identified. This might be the base of subducted crust, 3) located 35 to 45 km from the trench axis are several sub-parallel reflectors at 1 s above the top of the oceanic crust. These sub-parallel reflectors are also recognized at a central part of a strike profile, however there reflectors are not clear at the northern and southern end of the profile.
DE: 3025 Marine seismics (0935)
DE: 3040 Plate tectonics (8150, 8155, 8157, 8158)
DE: 7209 Earthquake dynamics and mechanics
DE: 7220 Oceanic crust
DE: 8120 Dynamics of lithosphere and mantle--general
SC: Tectonophysics [T]
MN: 2003 Fall Meeting