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Segmentation of the Vp/Vs ratio and low‐frequency earthquake distribution around the fault boundary of the Tonankai and Nankai earthquakes
Author(s) -
Akuhara Takeshi,
Mochizuki Kimihiro,
Nakahigashi Kazuo,
Yamada Tomoaki,
Shinohara Masanao,
Sakai Shin'ichi,
Kanazawa Toshihiko,
Uehira Kenji,
Shimizu Hiroshi
Publication year - 2013
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/grl.50223
Subject(s) - seismology , geology , slip (aerodynamics) , seismometer , physics , thermodynamics
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.