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Science 25 February 1994:
Vol. 263. no. 5150, pp. 1116 - 1118
DOI: 10.1126/science.263.5150.1116
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Articles

Double Seismic Zone for Deep Earthquakes in the Izu-Bonin Subduction Zone

Takashi Iidaka 1 and Yoshitsugu Furukawa 2

1 Earthquake Research Institute, University of Tokyo, Yayoi 1-1-1, Bunkyo, Tokyo, Japan
2 Department of Geology and Mineralogy, Faculty of Science, Kyoto University, Kyoto, Japan

A double seismic zone for deep earthquakes was found in the Izu-Bonin region. An analysis of SP-converted phases confirms that the deep seismic zone consists of two layers separated by sim20 kilometers. Numerical modeling of the thermal structure implies that the hypocenters are located along isotherms of 500° to 550°C, which is consistent with the hypothesis that deep earthquakes result from the phase transition of metastable olivine to a high-pressure phase in the subducting slab.

Submitted on September 23, 1993
Accepted on December 13, 1993

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