In situ stress state from walkaround VSP anisotropy in the Kumano Basin southeast of the Kii Peninsula, Japan

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doi: 10.1029/2011GC003583
Author(s): Tsuji, Takeshi; Hino, Ryota; Sanada, Yoshinori; Yamamoto, Kiyohiko; Park, Jin-Oh; No, Tetsuo; Araki, Eiichiro; Bangs, Nathan; von Huene, Roland; Moore, Gregory F.; Kinoshita, Masataka
Author Affiliation(s): Primary:
Kyoto University, Graduate School of Engineering, Kyoto, Japan
Tohoku University, Japan
Japan Agency for Marine-Earth Science and Technology, Japan
University of Tokyo, Japan
University of Texas at Austin, United States
University of California at Davis, United States
University of Hawaii at Manoa, United States
Volume Title: Geochemistry, Geophysics, Geosystems - G<sup>3</sup>
Source: Geochemistry, Geophysics, Geosystems - G>3`, Vol.12. Publisher: American Geophysical Union and The Geochemical Society, United States. ISSN: 1525-2027
Note: In English. 40 refs.; illus., incl. sketch map
Summary: To reveal the stress state within the Kumano basin, which overlies the Nankai accretionary prism, we estimated seismic anisotropy from walkaround vertical seismic profiling (VSP) data recorded at Site C0009 during Integrated Ocean Drilling Program (IODP) Expedition 319. We obtained the following anisotropic parameters: (1) P wave velocity anisotropy derived from azimuthal normal moveout (NMO) velocity analysis, (2) P wave amplitude variation with azimuth, and (3) axes of symmetry of S wave splitting. Azimuthal variations of P wave velocity by ellipsoidal fitting analysis showed that P wave velocity anisotropy within sediments of the Kumano basin was ∼5%. Both the directions of fast P wave velocity and strong amplitude are aligned with the convergence vector of the Philippine Sea plate. Furthermore, S wave splitting analysis indicated that S wave polarization axes were parallel to and normal to the direction of plate subduction. These results indicate that the maximum horizontal stress at Site C0009 in the Kumano basin is in the direction of plate subduction. The horizontal differential stress estimated from the P wave velocity anisotropy (2.7∼5.5 MPa) indicates that the maximum horizontal stress is similar in magnitude to (or a little higher than) the vertical stress.
Year of Publication: 2011
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 18 Geophysics, Solid-Earth; 20 Geophysics, Applied; Active faults; Amplitude; Anisotropy; Body waves; Crust; Downhole methods; Elastic waves; Expedition 319; Faults; Geophysical methods; Geophysical profiles; Geophysical surveys; IODP Site C0009; Integrated Ocean Drilling Program; Kumano Basin; Marine geology; NanTroSEIZE; North Pacific; Northwest Pacific; Oceanic crust; P-waves; Pacific Ocean; Philippine Sea Plate; Plate tectonics; S-waves; Seismic methods; Seismic profiles; Seismic waves; Seismicity; Stress; Subduction zones; Surveys; Tectonophysics; Velocity; Vertical seismic profiles; West Pacific
Coordinates: N332728 N332728 E1363209 E1363209
N323000 N343000 E1373000 E1353000
Record ID: 2013046517
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