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

Takeshi Tsuji, Ryota Hino, Yoshinori Sanada, Kiyohiko Yamamoto, Jin Oh Park, Tetsuo No, Eiichiro Araki, Nathan Bangs, Roland Von Huene, Gregory Moore, Masataka Kinoshita

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Abstract

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.

Original languageEnglish
Article numberQ0AD19
JournalGeochemistry, Geophysics, Geosystems
Volume12
Issue number9
DOIs
Publication statusPublished - Mar 1 2012
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Geochemistry and Petrology

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    Tsuji, T., Hino, R., Sanada, Y., Yamamoto, K., Park, J. O., No, T., Araki, E., Bangs, N., Von Huene, R., Moore, G., & Kinoshita, M. (2012). In situ stress state from walkaround VSP anisotropy in the Kumano basin southeast of the Kii Peninsula, Japan. Geochemistry, Geophysics, Geosystems, 12(9), [Q0AD19]. https://doi.org/10.1029/2011GC003583