Stress‐induced spatiotemporal variations in anisotropic structures beneath Hakone volcano, Japan, detected by <i>S</i> wave splitting: A tool for volcanic activity monitoring

DOI Web Site Web Site 被引用文献9件
  • Ryou Honda
    Hot Springs Research Institute of Kanagawa Prefecture Odawara Japan
  • Yohei Yukutake
    Hot Springs Research Institute of Kanagawa Prefecture Odawara Japan
  • Akio Yoshida
    Center for Integrated Research and Education of Natural Hazards Shizuoka University Shizuoka Japan
  • Masatake Harada
    Hot Springs Research Institute of Kanagawa Prefecture Odawara Japan
  • Kazuki Miyaoka
    Hot Springs Research Institute of Kanagawa Prefecture Odawara Japan
  • Mikio Satomura
    Hot Springs Research Institute of Kanagawa Prefecture Odawara Japan

書誌事項

公開日
2014-09
権利情報
  • http://onlinelibrary.wiley.com/termsAndConditions#vor
DOI
  • 10.1002/2014jb010978
公開者
American Geophysical Union (AGU)

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説明

<jats:title>Abstract</jats:title><jats:p>Hakone volcano, located at the northern tip of the Izu‐Mariana volcanic arc, Japan, has a large caldera structure containing numerous volcanic hot springs. Earthquake swarms have occurred repeatedly within the caldera. The largest seismic swarm since the commencement of modern seismic observations (in 1968) occurred in 2001. We investigated the anisotropic structure of Hakone volcano based on <jats:italic>S</jats:italic> wave splitting analysis and found spatiotemporal changes in the splitting parameters accompanying the seismic swarm activity. Depth‐dependent anisotropic structures are clearly observed. A highly anisotropic layer with a thickness of ~1.5 km is located beneath the Koziri (KZR) and Kozukayama (KZY) stations. The anisotropic intensity in the region reaches a maximum of 6–7% at a depth of 1 km and decreases markedly to less than 1% at a depth of 2 km. The anisotropic intensity beneath Komagatake station (KOM) decreases gradually from a maximum of 6% at the surface to 0% at a depth of 5 km but is still greater than 2.5% at a depth of 3 km. At KZY, the anisotropic intensity along a travel path of which the back azimuth was the south decreased noticeably after the 2001 seismic swarm activity. During the swarm activity, tilt meters and GPS recorded the crustal deformation. The observed decrease in anisotropic intensity is presumed to be caused by the closing of microcracks by stress changes accompanying crustal deformation near the travel path.</jats:p>

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