Segmentation of the Vp/Vs ratio and low-frequency earthquake distribution around the fault boundary of the Tonankai and Nankai earthquakes

Takeshi Akuhara, Kimihiro Mochizuki, Kazuo Nakahigashi, Tomoaki Yamada, Masanao Shinohara, Shin'Ichi Sakai, Toshihiko Kanazawa, Kenji Uehira, Hiroshi Shimizu

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

Beneath the Kii Peninsula, the distribution of low-frequency earthquakes (LFEs) forms three clusters. A previous study shows that one of the clusters has anomalously less amount of cumulative slip than the others. To understand the cause of this variation, we applied a tomographic analysis using arrival times of earthquakes recorded by both ocean bottom seismometers and onshore stations. As a result, we identified segmentation about the Vp/Vs ratio around the subducting plate interface corresponding to the distribution of LFEs. One of the segments has low a Vp/Vs ratio that coincides with the small-slip LFE cluster. Another segment has a high Vp/Vs ratio in which almost no LFEs occur. We conclude that the relatively low pore fluid pressure within the low Vp/Vs segment contributes to the small-slip LFE cluster and that the gap of LFEs within the high Vp/Vs segment corresponds to stable slip area due to high pore fluid pressure. Key Points Segmentation of Vp/Vs ratio along subduction margin Spatial relationship between Vp/Vs ratio 3-D velocity structure from offshore to onshore around the Kii Peninsula

Original languageEnglish
Pages (from-to)1306-1310
Number of pages5
JournalGeophysical Research Letters
Volume40
Issue number7
DOIs
Publication statusPublished - Apr 16 2013

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Earth and Planetary Sciences(all)

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