Spatial heterogeneity of the mantle wedge structure and interplate coupling in the NE Japan forearc region

Yojiro Yamamoto, Ryota Hino, Kensuke Suzuki, Yoshihiro Ito, Tomoaki Yamada, Masanao Shinohara, Toshihiko Kanazawa, Gen Aoki, Masayuki Tanaka, Kenji Uehira, Gou Fujie, Yoshiyuki Kaneda, Tetsuo Takanami, Toshinori Sato

Research output: Contribution to journalArticlepeer-review

18 Citations (Scopus)

Abstract

We performed 3-D seismic tomography in the forearc region of the northeastern Japan subduction zone using both onshore and offshore seismic station data. We obtained the Vp, Vs, and Vp/Vs structures around the plate boundary with high spatial resolution. The position of the plate boundary as defined by relocated hypocenters coincides with the sharp velocity boundary between the oceanic crust and the mantle wedge. The mantle wedge above the coseismic slip area of the 1978 and 2005 off-Miyagi interplate earthquakes (M > 7) is characterized by high Vp and Vs, but low Vp/Vs. Off Fukushima, however, where large earthquakes rarely occur, we found a high Vp/Vs anomaly at the tip of the mantle wedge. The spatial distribution of serpentinized mantle wedge limits the spatial extent of the strongly coupled area on the plate boundary, and thus can explain the difference in seismic activity between the off-Miyagi and off-Fukushima regions.

Original languageEnglish
Article numberL23304
JournalGeophysical Research Letters
Volume35
Issue number23
DOIs
Publication statusPublished - 2008 Dec 16

ASJC Scopus subject areas

  • Geophysics
  • Earth and Planetary Sciences(all)

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