HR: 1330h
AN: T52C-0287    [PDF]
TI: Pre-stack Depth Imaging of NanTroSEIZE Drill Targets in the Eastern Nankai Accretionary prism, Kumano Basin
AU: * Ike, T
EM: tike@Hawaii.edu
AF: SOEST, University of Hawaii, 1680 East-West Rd., POST 813, Honolulu, HI 96822
AU: Nakamura, Y
EM: saru@ori.u-tokyo.ac.jp
AF: Ocean Research Institute, Univ. Tokyo, Tokyo, 164-8639 Japan
AU: Costa Pisani, P
EM: pcosta@soest.hawaii.edu
AF: Ocean Research Institute, Univ. Tokyo, Tokyo, 164-8639 Japan
AU: Park, J
EM: jopark@jamstec.go.jp
AF: IFREE, JAMSTEC, Yokohama, 236-0001 Japan
AU: Okano, T
EM: tokano@jamstec.go.jp
AF: CDEX, JAMSTEC, Yokosuka, 237-0061 Japan
AU: Hashimoto, T
EM: thashimoto@jamstec.go.jp
AF: CDEX, JAMSTEC, Yokosuka, 237-0061 Japan
AU: Tanaka, H
EM: htanaka@jamstec.go.jp
AF: CDEX, JAMSTEC, Yokosuka, 237-0061 Japan
AU: Kuramoto, S
EM: s.kuramoto@jamstec.go.jp
AF: CDEX, JAMSTEC, Yokosuka, 237-0061 Japan
AU: Moore, G
EM: gmoore@Hawaii.edu
AF: SOEST, University of Hawaii, 1680 East-West Rd., POST 813, Honolulu, HI 96822
AU: Taira, A
EM: ataira@jamstec.go.jp
AF: CDEX, JAMSTEC, Yokosuka, 237-0061 Japan
AB: In support of the NanTroSEIZE proposal for IODP deep riser drilling into the seimogenic zone of the eastern Nankai Trough, CDEX contracted a commercial seismic reflection survey in spring, 2003. This new survey supplements a 2002 regional seismic survey by IFREE. We report the results of pre-stack depth migration (PSDM) of two dip lines from each survey that clarify the structure and velocity distribution around the proposed IODP drill targets. The seaward 25 km of the accretionary prism is characterized by imbricate thrust faults that sole into a well-imaged decollement. The width of the frontal thrust shear is variable along strike due to interaction with a small subducting seamount. There is a small, laterally discontinuous proto-thrust zone seaward (and in some places beneath), the frontal thrust. The subducting Shikoku Basin sediment secquence is about 500 m thick under the seaward part of the prism. At about 28 km from the deformation front (DF), the decollement steps down to near the top of oceanic crust. A splay fault rises from the plate boundary fault near the top of oceanic crust about 50 km from the DF at a depth of about 10 km. Its dip becomes steeper above the decollement step-down at 28 km and it cuts through the prism to near the sea floor at about 24 km from DF. The overlying sedimentary sequence in the Kumano forearc basin is progressively tilted landward with depth, reflecting uplift caused by motion along the splay fault.
DE: 3025 Marine seismics (0935)
DE: 8105 Continental margins and sedimentary basins
DE: 8150 Plate boundary--general (3040)
SC: Tectonophysics [T]
MN: 2003 Fall Meeting