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Science 29 August 2008:
Vol. 321. no. 5893, pp. 1194 - 1197
DOI: 10.1126/science.1160250
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Reports

Weak Interplate Coupling by Seamounts and Repeating M ~ 7 Earthquakes

Kimihiro Mochizuki,1* Tomoaki Yamada,1 Masanao Shinohara,1 Yoshiko Yamanaka,2 Toshihiko Kanazawa1

Subducting seamounts are thought to increase the normal stress between subducting and overriding plates. However, recent seismic surveys and laboratory experiments suggest that interplate coupling is weak. A seismic survey in the Japan Trench shows that a large seamount is being subducted near a region of repeating earthquakes of magnitude M ~ 7. Both observed seismicity and the pattern of rupture propagation during the 1982 M 7.0 event imply that interplate coupling was weak over the seamount. A large rupture area with small slip occurred in front of the seamount. Its northern bound could be determined by a trace of multiple subducted seamounts. Whereas a subducted seamount itself may not define the rupture area, its width may be influenced by that of the seamount.

1 Earthquake Research Institute, University of Tokyo, 1-1-1, Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan.
2 Graduate School of Environmental Studies, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan.

* To whom correspondence should be addressed. E-mail: kimi{at}eri.u-tokyo.ac.jp

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Science. ISSN 0036-8075 (print), 1095-9203 (online)