HR: 08:35h
AN: T51E-03    [Abstracts]
TI: Basin migration due to subduction erosion along the Japan Trench
AU: * Okamura, Y
EM: okamura-y@aist.go.jp
AF: Active Fault Research Center, GSJ/AIST, 1-1-1, Higashi, Tsukuba, 305-8567, Japan
AU: Arai, K
EM: ko-arai@aist.go.jp
AF: Institute of Geoinformation and Geoscience, GSJ/AIST, 1-1-1, Higashi, Tsukuba, 305-8567, Japan
AU: Sasaki, T
EM: tmsasaki@mail.ecc.u-tokyo.ac.jp
AF: University of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
AU: Tsujino, T
EM: t-tsujino@aist.go.jp
AF: Institute of Geoinformation and Geoscience, GSJ/AIST, 1-1-1, Higashi, Tsukuba, 305-8567, Japan
AU: Inoue, T
EM: inoue-taku @aist.go.jp
AF: Institute of Geoinformation and Geoscience, GSJ/AIST, 1-1-1, Higashi, Tsukuba, 305-8567, Japan
AU: Satake, K
EM: kenji.satake @aist.go.jp
AF: Active Fault Research Center, GSJ/AIST, 1-1-1, Higashi, Tsukuba, 305-8567, Japan
AB: Basin migration in the forearc basin along the Japan Trench was imaged by high-resolution seismic profiles and the migration was attributed to the migration of the zone of intense subduction erosion at the base of the forearc wedge. The Japan Trench is a classic example of subduction erosion. Studies of drill cores of DSDP Legs 56 and 57 showed that the forearc basin has been subsiding 3 to 4 km since the latest Oligocene time. These previous studies have not assumed uneven subsidence or basin migration through the 100 km wide forearc wedge. We obtained high-resolution seismic profiles of the forearc basins along the Japan Trench using GI gun and 48 channel digital streamer. The aim of the survey is to examine the relationship between geologic structure and a source area of the subduction zone earthquakes. The profiles show that the topographically flat forearc basin has narrower depocenters which have been migrating landward. The velocity of the migration is much slower than the convergent rate between the Pacific Plate and the NE Japan arc, indicating that the migration was not caused by passage of seamount or ridges on the subducting Pacific plate. These preliminary analyses support the idea that the subduction erosion occurs in limited areas which have been migrating landward. The basin migration of the forearc basin provides important information how subduction erosion proceeds.
DE: 3025 Marine seismics (0935, 7294)
DE: 7240 Subduction zones (1207, 1219, 1240)
DE: 8015 Local crustal structure
DE: 8170 Subduction zone processes (1031, 3060, 3613, 8413)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting