HR: 0830h
AB: The Nankai trough is located in the boudary between the Philippine Sea plate and the Eurasia plate, and the Nankai accretionary prism has been developed landward of the Nankai trough. The Nankai great earthquakes has been repeatedly generated in the Nankai trough at $\sim$100 year intervals for the past over 1,000 years. We conducted a 3-D seismic reflection survey in the western Nankai trough off Muroto cape using R/V Maurice Ewing. We could acquire the seismic data which covers 80 $\times$ 8km size 3-D box. The obtained preliminary result shows a detail image of the accretionary prism and the seismogenic zone in the Nankai trough. The top of the oceanic crust and decollement can be traced from the deformation front 40km landward, and decollement is converged to the top of the oceanic crust near the updip limit of the seismogenic zone. Large out-of-sequence thrusts develop in the zone which starts at 30km landward from the deformation front and follows 20km long. In this zone, the accretionary prism forms a slope uplifting landward and the water depth changes from $\sim$ 4000 to 3000 m. These thrusts are also converged to the top of oceanic crust or decollement at the updip limit of the seismogenic zone. Preliminary 3-D interpretation of these thrusts faults shows that each thrust does not lie in a flat plain but has a curtain-like shape with undulation. In this paper, we will present a result of the detail analysis focusing on the large thrust zone to obtain a fine image of this area. This image will be a aid to reveal the mechanism of the disastrous earthquake in the Nankai trough.
AN: T51A-11
TI: 3-D Seismic Imaging of the Large Thrust Zone in the Nankai Trough
AU: * Nakamura, Y
EM: saru@ori.u-tokyo.ac.jp
AF: Ocean Research Institute, University of Tokyo, 1-15-1 Minamidai, Nakano, Tokyo, 164-8639 Japan
AU: Kuramoto, S
AF: Geological Survey of Japan, 1-1-3 Higashi, Tsukuba, 305-8657 Japan
AU: Taira, A
AF: Ocean Research Institute, University of Tokyo, 1-15-1 Minamidai, Nakano, Tokyo, 164-8639 Japan
AU: Bangs, N L
AF: Institute for Geophysics, University of Texas at Austin , 4412 Spicewood Springs Rd., Bldg. 600, Austin, TX 78759 United States
AU: Shipley, T H
AF: Institute for Geophysics, University of Texas at Austin , 4412 Spicewood Springs Rd., Bldg. 600, Austin, TX 78759 United States
AU: Moore, G F
AF: Dept. Geology and Geophysics, University of Hawaii, 1680 East-West Rd., Honolulu, HI 96822 United States
AU: Zhao, Z
AF: Institute for Geophysics, University of Texas at Austin , 4412 Spicewood Springs Rd., Bldg. 600, Austin, TX 78759 United States
AU: Gulick, S S
AF: Institute for Geophysics, University of Texas at Austin , 4412 Spicewood Springs Rd., Bldg. 600, Austin, TX 78759 United States
AU: Hills, D J
AF: Dept. Geology and Geophysics, University of Hawaii, 1680 East-West Rd., Honolulu, HI 96822 United States
AU: Park, J
AF: Japan Marine Science and Technology Center , 2-15 Natsushima-cho, Yokosuka, 237-0061 Japan
AU: Mochizuki, K
AF: Ocean Research Institute, University of Tokyo, 1-15-1 Minamidai, Nakano, Tokyo, 164-8639 Japan
DE: 8105 Continental margins and sedimentary basins
DE: 8150 Plate boundary--general (3040)
DE: 5102 Acoustic properties
DE: 3000 MARINE GEOLOGY AND GEOPHYSICS
DE: 3025 Marine seismics (0935)
SC: T
MN: Fall Meeting 2000