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Seismic structure of the northern end of the Ryukyu Trench subduction zone, southeast of Kyushu, Japan
Earth, Planets and Space volume 61, pagese37–e40(2009)
P-wave velocity models related to the Philippine Sea plate subduction have been obtained from seismic explorations at the northern end of the Nansei-Shoto (Ryukyu) Trench. Both multi-channel seismic reflection and ocean bottom seismographic records provide clear images of the rough seafloor topography and irregular P-wave velocity structure of the northwestern extension of the Kyushu-Palau Ridge and Amami Plateau below the landward trench slope. Low velocity (V p ≤ 4–5 km/s) and thick (>7 km) materials above the plate boundary characterize the landward trench slope structure. An exception to this is found where the subducting plate contacts higher velocity (V p > 5 km/s) materials of the landward plate at the estimated position of the seismic asperity of 1968 Hyuganada earthquake (Mw 7.5).
Fujie, G., J. Kasahara, T. Sato, and K. Mochizuki, Traveltime and raypath computation: A new method in a heterogeneous medium, J. Soc. Explor. Geophys. Jpn., 53, 1–11, 2000.
Ichikawa, G., Ocean bottom seismographic experiment to study crustal structure in Hyuga-nada, Master’s Thesis, Hokkaido University, Sapporo, Japan, 1997 (in Japanese).
Iwasaki, T. et al., Crustal and upper mantle structure in the Ryukyu Island Arc deduced from deep seismic sounding, Geophys. J. Int., 102, 631–651, 1990.
Kasahara et al., A new integrated method for the crustal structure analysis using OBSs and control sources, Eos Trans. AGU, 88(52), Fall Meet. Suppl., Abstract S12A–06, 2007.
Kodaira, S., T. Iwasaki, T. Urabe, T. Kanazawa, F. Egloff, J. Makris, and H. Shimamura, Crustal structure across the middle Ryukyu trench obtained from ocean bottom seismographic data, Tectonophysics, 263, 39–60, 1996.
Korenaga, J., W. S. Holbrook, G. M. Kent, P. B. Kelemen, R. S. Detrick, H.-C. Larsen, J. R. Hopper, and T. Dahl-Jensen, Crustal structure of the southeast Greenland margin from joint refraction and reflection seismic tomography, J. Geophys. Res., 105, 21591–21614, 10.1029/2000JB900188, 2000.
Kubota, R., E. Nishiyama, K. Murase, and J. Kasahara, Traveltime estimation of first arrivals and later phases using the modified graph method for a crustal structure analysis, Explor. Geophys., 40, 105–113, 2009.
Larsen, S. C. and C. A. Schultz, ELAS3D: 2D/3D elastic finite-difference wave propagation code, LLNL internal report, 18 p., 1995.
Nishizawa, A., K. Kaneda, Y. Katagiri, and J. Kasahara, Variation in crustal structure along the Kyushu-Palau Ridge at 15–21°N on the Philippine Sea plate based on seismic refraction profiles, Earth Planets Space, 59, e17–e20, 2007.
Nishizawa, A., K. Kaneda, N. Watanabe, and M. Oikawa, Seismic structure of the subducting seamounts on the trench axis: Erimo Seamount and Daiichi-Kashima Seamount, northern and southern ends of the Japan Trench, Earth Planets Space, 61, e5–e8, 2009.
Noda et al., Preliminary report of multi-channel and wide-angle seismic surveys at the northern Kyushu-Palau Ridge (KPr4), the Daito Ridge and Amami Plateau (DAr2) and the mid Shikoku Basin (SPr7), Technical Bull. Hydrogr. Oceanogr., 42, 2006 (in Japanese).
Oshida, A., R. Kubota, E. Nishiyama, J. Ando, J. Kasahara, A. Nishizawa, and K. Kaneda, A new method for determining OBS positions for crustal structure studies, using airgun shots and precise bathymetric data, Explor. Geophys., 39, 15–25, 2008.
Tanaka et al., Preliminary report of multi-channel and wide-angle seismic experiments in the vicinity of Kyushu-Palau Ridge (KPr1, KPr2 and SPr10) and traversing the Minami Daito Basin, Daito Ridge and Kyushu-Palau Ridge (DAr5), Technical Bull. Hydrogr. Oceanogr., 44, 2008 (in Japanese).
The Headquarters for Earthquake Research Promotion, Evaluations of occurrence potentials of subduction-zone earthquakes to date, http://www.jishin.go.jp/main/chousa/04febhyuganada/index.html, 2004 (in Japanese).
Wessel, P. and W. H. F. Smith, New, improved version of the Generic MappingTools released, Eos Trans. AGU, 79, 579, 1998.
Yagi, Y., M. Kikuchi, S. Yoshida, and Y. Yamanaka, Source Process of the Hyuga-nada earthquake of April 1, 1968 (Mjma 7.5), and relationship to the subsequent seismicity, Zisin, 51, 139–148, 1998 (in Japanese with English abstract).
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Nishizawa, A., Kaneda, K. & Oikawa, M. Seismic structure of the northern end of the Ryukyu Trench subduction zone, southeast of Kyushu, Japan. Earth Planet Sp 61, e37–e40 (2009). https://doi.org/10.1186/BF03352942
- Marine seismics
- Ryukyu (Nansei Shoto) Trench
- Kyushu-Palau Ridge
- Philippine Sea plate subduction