HR: 1330h
AN: T52C-0291    [PDF]
TI: Detailed Structure of the Large Thrust Slice Zone in the Nankai Trough off Muroto
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: Bangs, N L
EM: nathan@ig.utexas.edu
AF: Institute for Geophysics, Univ. Texas, Austin, TX 78759 United States
AU: Gulick, S P
EM: sean@ig.utexas.edu
AF: Institute for Geophysics, Univ. Texas, Austin, TX 78759 United States
AU: Moore, G F
EM: gmoore@Hawaii.edu
AF: SOEST, Univ. Hawaii, Honolulu, HI 96822 United States
AU: Kuramoto, S
EM: s.kuramoto@jamstec.go.jp
AF: CDEX, JAMSTEC, Yokosuka, 237-0061 Japan
AU: Shipley, T H
EM: tom@ig.utexas.edu
AF: Institute for Geophysics, Univ. Texas, Austin, TX 78759 United States
AU: Taira, A
EM: ataira@jamstec.go.jp
AF: CDEX, JAMSTEC, Yokosuka, 237-0061 Japan
AB: A 3D seismic reflection data set were collected in the Nankai trough off cape Muroto in 1999. Pre-stack time migration has been perfomed on the 3D data. We will present on the detailed structure of the large thrust slice zone revealed from the 3D seismic reflection volume. The Large Thrust Slize Zone (LTSZ) with $\sim$25km length is located $\sim$40km landward from the deformation front, where the water depth shallows to 3000m from 4000m. The LTSZ is characterized by the imbricate structure which is also recognized in the frontal thrust zone, and thrust faults developed in the accretionary prism, which suggests that old accretionary prism in the LTSZ has been uplifted by the underplating and thrust faulting. Several faults can be traced in the LTSZ. These faults cut the well stratified imbricate thrust packages. Imbricate package beneath the upper slope area is thicker than that beneath the lower slope area. Strong flat reflectors were imaged beneath the base of the slope. These reflectors are terminated by a low angle fault landward. This setting of flat reflectors and a low angle fault is similar with that at the deformation front off Kumano area. The low angle fault might be a remnant decollement. The flat reflectors are clearly imaged in the southwest half of the 3D box, but not clear in the northeastern part. Low angle landward dipping reflectors (LA-LDRs) are imaged at the depth of 6.5-6.7s beneath the upper slope of whole 3D box. The LA-LDRs accompany with sigmoidal reflection events, which may represent a duplex structure. Some of the thrust faults take off from the landward end of LA-LDRs.
DE: 3000 MARINE GEOLOGY AND GEOPHYSICS
DE: 8105 Continental margins and sedimentary basins
DE: 8150 Plate boundary--general (3040)
SC: Tectonophysics [T]
MN: 2003 Fall Meeting