HR: 0800h
AN: T41C-0698    [Abstracts]
TI: The relationship between the seismic characteristics of crustal structure in Shikoku Basin and en-echelon arrangement
AU: * Yamashita, M
EM: mikiya@jamstec.go.jp
AF: IFREE, JAMSTEC, 3173-25 Showa-machi, Kanazawa-ku, Yokohama Kanagawa, 236-0001, Japan
AU: Takahashi, N
EM: narumi@jamstec.go.jp
AF: IFREE, JAMSTEC, 3173-25 Showa-machi, Kanazawa-ku, Yokohama Kanagawa, 236-0001, Japan
AU: Kodaira, S
EM: kodaira@jamstec.go.jp
AF: IFREE, JAMSTEC, 3173-25 Showa-machi, Kanazawa-ku, Yokohama Kanagawa, 236-0001, Japan
AU: No, T
EM: not@jamstec.go.jp
AF: IFREE, JAMSTEC, 3173-25 Showa-machi, Kanazawa-ku, Yokohama Kanagawa, 236-0001, Japan
AU: Takizawa, K
EM: takizawak@jamstec.go.jp
AF: IFREE, JAMSTEC, 3173-25 Showa-machi, Kanazawa-ku, Yokohama Kanagawa, 236-0001, Japan
AU: Miura, S
EM: miuras@jamstec.go.jp
AF: IFREE, JAMSTEC, 3173-25 Showa-machi, Kanazawa-ku, Yokohama Kanagawa, 236-0001, Japan
AU: Kaiho, Y
EM: kaihoy@jamstec.go.jp
AF: IFREE, JAMSTEC, 3173-25 Showa-machi, Kanazawa-ku, Yokohama Kanagawa, 236-0001, Japan
AU: Sato, T
EM: tsato@jamstec.go.jp
AF: IFREE, JAMSTEC, 3173-25 Showa-machi, Kanazawa-ku, Yokohama Kanagawa, 236-0001, Japan
AU: Kaneda, Y
EM: kaneday@jamstec.go.jp
AF: IFREE, JAMSTEC, 3173-25 Showa-machi, Kanazawa-ku, Yokohama Kanagawa, 236-0001, Japan
AB: Detailed crustal structure information of a back-arc basin must be obtained to elucidate the mechanism of its opening. Especially, the Shikoku Basin, which occupies the northern part of the Philippine Sea Plate between the Kyushu-Palau Ridge and the Izu-Ogasawara Arc, is an important area to elucidate the evolution of the back-arc basins as a part of the growth process of the Philippine Sea. Japan Agency for Marine-Earth Science and Technology (JAMSTEC) carried out multi-channel seismic reflection survey using 12,000 cu.in. air gun and streamer with 204 ch hydrophones in the Izu-Ogasawara region since 2004. The total length of survey lines is more than 10,000 km until 2006. We investigate the crustal structure beneath the Shikoku Basin along 10 survey lines, which are across to the strike of the en-echelon seamount chains in the rear arc. From the seismic profiles, some faults and intrusion structures are obtained in the Shikoku Basin. The deformation structure with acoustic basement is widely distributed between the Shikoku Basin and the Izu-Ogasawara arc. Some intrusions structure is identified in the Shikoku Basin are exposed on seafloor. The intrusions structure is assumed to locate in the extended region of the en-echelon arrangement. The strike-slip faults with flower structure cutting whole sediments are located in the arc-backarc transition zone in the northern Shikoku Basin, suggesting that this region is in share stress. On the other hand, these structures indicating the deformation and intrusions are not recognized in the eastern side of the Kyushu-Palau Ridge. The Izu-Ogasawara arc is colliding to the Japan Island arc in the Sagami Bay. In the Nankai Trough, the Philippine Sea plate is subducting to the Japan Island arc. Therefore, the strike-slip and reverse fault would be developed by the compression stress in the eastern side of Philippine Sea plate. If the en-echelon arrangement is developed along these faults, the intrusions structure obtained by our surveys correspond the tip of en-echelon arrangement. We will also discuss the effect with regard to back-arc opening and post volcanism.
DE: 1734 Seismology
DE: 1744 Tectonophysics
DE: 3001 Back-arc basin processes
DE: 3025 Marine seismics (0935, 7294)
DE: 7220 Oceanic crust
SC: Tectonophysics [T]
MN: 2007 Fall Meeting