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Seismotectonic implications of the Kyushu-Palau ridge subducting beneath the westernmost Nankai forearc
Earth, Planets and Space volume 61, pages1013–1018(2009)
The Kyushu-Palau ridge, a remnant arc on the Philippine Sea Plate, subducts beneath the Eurasian Plate along the westernmost part of the Nankai Trough. A seismic reflection profile on strike line images the ∼70-km-wide Kyushu-Palau ridge where it subducts beneath the toe of the forearc accretionary wedge. The geomagnetic anomaly signature, seafloor topographic features, wide-angle refraction data, and on-land geomorphologic evidence enable us to trace the forearc extension of the subducted ridge up to the east Kyushu. The subducted Kyushu-Palau ridge with excess mass may be relatively buoyant, and thus is more likely to resist subduction upon collision with the overriding plate at depth, leading us to speculate that there is locally large tectonic stress at the contact zone between the subducted ridge and base of the overriding plate. The large stress zone is marked by historic thrust-type intermediate-class (magnitude 6 or 7) earthquakes. The flank regions of the subducted buoyant Kyushu-Palau ridge are more likely to tear and result in slab fracturing when the ridge subducts deeper. We propose that the subducted Kyushu-Palau ridge may serve not only as a seismic asperity at depth but also produce the slab fracture as a seismic barrier inhibiting the rupture propagation of the adjacent megathrust earthquakes in the Hyuga segment.
Abercrombie, R. E., M. Antolik, K. Felzer, and G. Ekstrom, The 1994 Java tsunami earthquake: Slip over a subducting seamount, J. Geophys. Res., 106, 6595–6607, 2001.
Ando, M., Source mechanisms and tectonic significance of historical earthquakes along the Nankaki trough, Tectonophysics, 27, 119–140, 1975.
Bilek, S. L., S. Y. Schwartz, and H. R. DeShon, Control of seafloor roughness on earthquake rupture behavior, Geology, 31, 455–458, 2003.
Christensen, D. H. and T. Lay, Large earthquakes in the Tonga region associated with subduction of the Louisville Ridge, J. Geophys. Res., 93, 13367–13389, 1988.
Cloos, M., Thrust-type subduction zone earthquakes and seamount asperities: A physical model for seismic rupture, Geology, 20, 601–604, 1992.
Dominguez, S., J. Malavieille, and S. E. Lallemand, Deformation of accretionary wedge in response to seamount subduction: Insights from sandbox experiments, Tectonics, 19, 182–196, 2000.
Geological Survey of Japan (GSJ) and Coordinating Committee for Coastal and Offshore Geoscience Programs (CCCOGP) in East and Southeast Asia, Magnetic anomaly map of east Asia 1:4,000,000 CDROM version. 1996.
Gutscher, M.-A., J. Malavieille, S. Lallemand, and J.-Y. Collot, Tectonic segmentation of the North Andean margin: impact of the Carnegie Ridge collision, Earth Planet. Sci. Lett., 168, 255–270, 1999.
Ichikawa, G., Ocean bottom seismographic experiment to study crustal structure in Hyuga-nada, M.Sc. Thesis, University of Hokkaido, 1997 (in Japanese with English abstract).
Ishihara, K. and A. Yoshida, Configuration of the Philippine sea slab and seismic activity in and around Kyushu, Zisin, 45, 45–51, 1992 (in Japanese with English abstract).
Kakuta, T., H. Miyamachi, and A. Takagi, Intermediate earthquakes in a northern part of the Kyushu-Ryukyu arc, Zisin, 44, 63–74, 1991 (in Japanese with English abstract).
Kelleher, J. and W. McCann, Buoyant zones, great earthquakes, and unstable boundaries of subduction, J. Geophys. Res., 81, 4885–4896, 1976.
Kobayashi, K. and M. Nakada, Magnetic anomalies and tectonic evolution of the Shikoku inter-arc basin, J. Phys. Earth, 26, S391–S402, 1978.
Kodaira, S., N. Takahashi, A. Nakanishi, S. Miura, and Y. Kaneda, Subducted seamount imaged in the rupture zone of the 1946 Nankaido earthquake, Science, 289, 104–106, 2000.
Le Pichon, X., T. Iiyama, H. Chamley, J. Charvet, M. Faure, H. Fujimoto, T. Furuta, Y. Ida, H. Kagami, S. Lallemant, J. Leggett, A. Murata, H. Okada, C. Rangin, V. Renard, A. Taira, and H. Tokuyama, The eastern and western ends of Nankai Trough: results of Box 5 and Box 7 Kaiko survey, Earth Planet. Sci. Lett., 83, 199–213, 1987.
Le Pichon, X., S. Lallemant, H. Tokuyama, E. Thoue, P. Huchon, and P. Henry, Structure and evolution of the backstop in the eastern Nankai trough area (Japan): Implications for the soon-to-come Tokai earthquake, Island Arc, 5, 440–454, 1996.
Liu, Z. and N. Bleistein, Migration velocity analysis: Theory and an iterative algorithm, Geophysics, 60, 142–153, 1995.
Mochizuki, K., T. Yamada, M. Shinohara, Y. Yamanaka, and T. Kanazawa, Weak interplate coupling by seamounts and repeating M∼7 earthquakes, Science, 321, 1194–1197, 2008.
Nagamune, T. and H. Tashiro, Shape of the Wadati-Benioff zone beneath Kyushu, Japan, Zisin, 42, 13–19, 1989 (in Japanese with English abstract).
Nakada, M., M. Tahara, H. Shimizu, S. Nagaoka, K. Uehira, and S. Suzuki, Late Pleistocene crustal uplift and gravity anomaly in the eastern part of Kyushu, Japan, and its geophysical implications, Tectonophysics, 351, 263–283, 2002.
Nishimura, S., M. Ando, and S. Miyazaki, Inter-plate coupling along the Nankai Trough and southeastward motion along southern part of Kyushu, Zisin, 51, 443–456, 1999 (in Japanese with English abstract).
Okino, K., Y. Shimakawa, and S. Nagaoka, Evolution of the Shikoku Basin, J. Geomag. Geoelectr., 46, 463–479, 1994.
Park, J.-O., G. F. Moore, T. Tsuru, S. Kodaira, and Y. Kaneda, A subducted oceanic ridge influencing the Nankai megathrust earthquake rupture, Earth Planet. Sci. Lett., 217, 77–84, 2003.
Scholz, C. H. and C. Small, The effect of seamount subduction on seismic coupling, Geology, 25, 487–490, 1997.
Seno, T., S. Stein, and A. E. Gripp, A model for the motion of the Philippine Sea plate consistent with NUVEL-1 and geological data, J. Geophys. Res., 98, 17941–17948, 1993.
Shiono, K., T. Mikumo, and Y. Ishikawa, Tectonics of the Kyushu-Ryukyu arc as evidenced from seismicity and focal mechanisms of shallow to intermediate depth earthquakes, J. Phys. Earth, 28, 17–43, 1980.
Spence, W., C. Mendoza, E. R. Engdahl, G. L. Choy, and E. Norabuena, Seismic subduction of the Nazca Ridge as shown by the 1996–97 Peru earthquakes, Pure Appl. Geophys., 154, 753–776, 1999.
Sugiyama, Y., Neotectonics of Southwest Japan due to the right-oblique subduction of the Philippine Sea Plate, Geofis. Int., 33, 53–76, 1994.
Tahara, M., K. Uehira, H. Shimizu, M. Nakada, T. Yamada, K. Mochizuki, M. Shinohara, M. Nishino, R. Hino, H. Yakiwara, H. Miyamachi, K. Umakoshi, M. Goda, N. Matsuwo, and T. Kanazawa, Seismic velocity structure around the Hyuganada region, Southwest Japan, derived from seismic tomography using land and OBS data and its implications for interplate coupling and vertical crustal uplift, Phys. Earth Planet. Inter., 167, 19–33, 2008.
Uehira, K., The stress field of the Hyuga-nada region, southwest Japan, deduced from ocean-bottom seismic observations, D.Sc. Thesis, University of Tokyo, 2007 (in Japanese with English abstract).
von Huene, R., C. R. Ranero, W. Weinrebe, and K. Hinz, Quaternary convergent margin tectonics of Costa Rica, segmentation of the Cocos plate, and Central American volcanism, Tectonics, 19, 314–334, 2000.
Yagi, Y., M. Kikuchi, S. Yoshida, and Y. Yamanaka, Source process of the Hyuga-nada earthquake of April 1, 1968 (MJMA 7.5), and its relationship to the subsequent seismicity, Zisin, 51, 139–148, 1998 (in Japanese with English abstract).
Yagi, Y., M. Kikuchi, S. Yoshida, and T. Sagiya, Comparison of the coseismic rupture with the aftershock distribution in the Hyuga-nada earthquakes of 1996, Geophys. Res. Lett., 26, 3161–3164, 1999.
Yamazaki, T. and Y. Okamura, Subducting seamounts and deformation of overriding forearc wedges around Japan, Tectonophysics, 160, 207–229, 1989.
Yanez, G. A., C. R. Ranero, R. von Huene, and J. Diaz, Magnetic anomaly interpretation across the southern central Andes (32°–34°): The role of the Juan Fernandez Ridge in the late Tertiary evolution of the margin, J. Geophys. Res., 106, 6325–6345, 2001.
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Park, JO., Hori, T. & Kaneda, Y. Seismotectonic implications of the Kyushu-Palau ridge subducting beneath the westernmost Nankai forearc. Earth Planet Sp 61, 1013–1018 (2009). https://doi.org/10.1186/BF03352951
- Kyushu-Palau ridge
- Nankai Trough
- reflection profile