3-D seismic images of thrust systems along the NanTroSEIZE Kumano Basin transect, southwestern Japan

Author(s): Bangs, N. L.; Moore, G. F.; Yoro, T.; Tanaka, H.; Gulick, S. P.
Author Affiliation(s): Primary:
University of Texas, Institute for Geophysics, Austin, TX, United States
Other:
Japan Agency for Marine-Earth Science and Technology, Japan
JAPEX Overseas Exploration, Japan
Volume Title: AGU 2006 fall meeting
Source: Eos, Transactions, American Geophysical Union, 87( Fall Meeting Suppl.); American Geophysical Union 2006 fall meeting, San Francisco, CA, Dec. 11-15, 2006. Publisher: American Geophysical Union, Washington, DC, United States. ISSN: 0096-3941 CODEN: EOSTAJ
Note: In English. Accessed on Sept. 25, 2007
Summary: In April-May 2006 we acquired new 3-D seismic reflection data across the Nankai Trough subduction zone of southwestern Japan along the NanTroSEIZE transect. The data were collected to image the subduction zone thrust system and the Kumano basin in preparation for IODP NanTroSEIZE drilling. We acquired the 3-D data with Petroleum GeoServices (PGS) on the S/V Nordic Explorer using four 4,500 m streamers with 150 m separation and two 3090 m3 sources firing alternately at 37.5 m intervals. These data have now been processed by PGS through dip moveout, and post-stack migration. (For more details on data acquisition and processing see Moore et al., this session.) The resulting 3-D data set covers a 12 x 56 km area that extends from the Kumono basin seaward to within 4 km of the deformation front in the dip direction and extends along strike ≈ 4 km northeast and ≈ 8 km southwest of the planned NanTroSEIZE drilling sites. From preliminary examination, the new data reveal excellent details of a complex 3-D network of thrust faults across this segment of the Nankai Trough. Along the lower slope the primary thrusts that extend through the accretionary wedge and sole into the basal décollement are highly irregular with 1.5-2.5 km down dip spacing and typical along strike extents of ≈ 1-3 km. These faults are recognizable by the displacement of the deformed stratigraphic horizons that comprise the accretionary wedge and are irregular in part due to the active subduction of an underlying seamount. Beneath the upper slope and Kumano basin, we image a splay fault system that can be traced from deep below the accrectionary wedge at ≈ 7 s (≈ 10 km depth), where it lies ≈ 0.5 s (≈ 1 km) above the top of the subducting crust, discontinuously up through the accretionary wedge along several branches to the seafloor. Deep segments of the splay fault are continuous along strike across the entire 12 km survey width, with shallower segments continuing typically 3-5 km along strike. Many segments along the splay fault system have reversed polarity reflections relative to the seafloor, high amplitudes relative to adjacent stratigraphic horizons, and are potentially active fluid conduits fed by deep sources.
Year of Publication: 2006
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 18 Geophysics, Solid-Earth; 20 Geophysics, Applied; Accretionary wedges; Asia; Far East; Faults; Geophysical methods; Geophysical surveys; Imagery; Integrated Ocean Drilling Program; Japan; Kumano Basin; NanTroSEIZE; Nankai Trough; North Pacific; Northwest Pacific; Pacific Ocean; Plate tectonics; Seismic methods; Southwestern Japan; Surveys; Three-dimensional models; Thrust faults; Thrust sheets; West Pacific
Record ID: 2009007566
Copyright Information: GeoRef, Copyright 2018 American Geosciences Institute.

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