HR: 0830h
AN: S41A-15    [Abstracts]
TI: Long-offset and multi-fold ocean bottom seismographic survey for imaging lithospheric scale structures in plate convergent margins
AU: * Kodaira, S
EM: kodaira@jamstec.go.jp
AF: Institute for Research on Earth Evolution (IFREE) Japan Agency for Marine-Earth Science and Technology, Showa-machi 3175-25, Kanazawa-ku, Yokohama, 236-0001 Japan
AU: Takahashi, N
EM: narumi@jamstec.go.jp
AF: Institute for Research on Earth Evolution (IFREE) Japan Agency for Marine-Earth Science and Technology, Showa-machi 3175-25, Kanazawa-ku, Yokohama, 236-0001 Japan
AU: Nakanishi, A
EM: ann@jamstec.go.jp
AF: Institute for Research on Earth Evolution (IFREE) Japan Agency for Marine-Earth Science and Technology, Showa-machi 3175-25, Kanazawa-ku, Yokohama, 236-0001 Japan
AU: Fujie, G
EM: fujie@jamstec.go.jp
AF: Institute for Research on Earth Evolution (IFREE) Japan Agency for Marine-Earth Science and Technology, Showa-machi 3175-25, Kanazawa-ku, Yokohama, 236-0001 Japan
AU: Ito, A
EM: iaki@jamstec.go.jp
AF: Institute for Research on Earth Evolution (IFREE) Japan Agency for Marine-Earth Science and Technology, Showa-machi 3175-25, Kanazawa-ku, Yokohama, 236-0001 Japan
AU: Miura, S
EM: miuras@jamstec.go.jp
AF: Institute for Research on Earth Evolution (IFREE) Japan Agency for Marine-Earth Science and Technology, Showa-machi 3175-25, Kanazawa-ku, Yokohama, 236-0001 Japan
AU: Sato, T
EM: tsato@jamstec.go.jp
AF: Institute for Research on Earth Evolution (IFREE) Japan Agency for Marine-Earth Science and Technology, Showa-machi 3175-25, Kanazawa-ku, Yokohama, 236-0001 Japan
AU: Tsuru, T
EM: tsurut@jamstec.go.jp
AF: Institute for Research on Earth Evolution (IFREE) Japan Agency for Marine-Earth Science and Technology, Showa-machi 3175-25, Kanazawa-ku, Yokohama, 236-0001 Japan
AU: Park, J
EM: jopark@jamstec.go.jp
AF: Institute for Research on Earth Evolution (IFREE) Japan Agency for Marine-Earth Science and Technology, Showa-machi 3175-25, Kanazawa-ku, Yokohama, 236-0001 Japan
AU: Kaneda, Y
EM: kaneday@jamstec.go.jp
AF: Institute for Research on Earth Evolution (IFREE) Japan Agency for Marine-Earth Science and Technology, Showa-machi 3175-25, Kanazawa-ku, Yokohama, 236-0001 Japan
AB: Recent availability of a large number of ocean bottom seismographs (OBSs), a large volume of air-gun array and a long streamer cable for academics provide several new findings of lithospheric scale structures in plate convergent margins. Japan Agency for Marine-Earth Science and Technology (JAMSTEC) has acquired long-offset seismic data using a super-densely deploy OBS (i.e. 1 - 5 km spacing OBSs along 100 - 500 km long profiles) since 1999. Long-offset multichannel seismic (MCS) data by a two-ship experiment, as well as conventional 2D MCS data, have been also acquired at a part of the profiles. Some of those profiles have been designed as combined onshore - offshore profiles for imaging a land-ocean transition zone. In a plate convergent margin, an oceanic plate subducts deep into a lithosphere and an island arc crust grows due to an accretion of melts welling up from subducted materials. Our obtained long-offset and multi-fold seismic data successfully provide fine images of subducting and overriding plates, which had not been imaged by conventional type of wide-angle seismic survey, in those complicated tectonic setting. One of the most striking findings is an image of several scales of subducted seamounts/ridges in the Nankai trough seismogenic zone, the SW Japan. We detected the subducted seamount/ridges, which are 50 - 100 km wide, distributing from near trough axis to ~ 40 km deep beneath the Japanese island. An important aspect, from a point of view of a geodynamic process, those structures are strongly correlated with slip zones of magnitude 8-class earthquakes, i.e.; subducted seamounts/ridge control the rupture propagations. We have also acquired very long offset seismic data (more than 500 km long) along and across the Izu-Bonin-Mariana (IBM) subduction zone in which ongoing crustal accretion process is proposed. Although the data is still processing, we expect, from our data, new and important information for the crustal accretion process at the IBM, because the crustal accretion is mainly proceed at the middle to lower crust, which have never been imaged without long-offset seismic data
DE: 7209 Earthquake dynamics and mechanics
DE: 7220 Oceanic crust
DE: 8105 Continental margins and sedimentary basins
DE: 8123 Dynamics, seismotectonics
DE: 8180 Tomography
SC: Seismology [S]
MN: 2005 Joint Assembly