Resistivity structure around the hypocentral area of the 1984 Western Nagano Prefecture earthquake in central Japan

• Kasaya Takafumi

  Disaster Prevention Research Institute, Kyoto University

• Oshiman Naoto

  Disaster Prevention Research Institute, Kyoto University

• Sumitomo Norihiko

  Disaster Prevention Research Institute, Kyoto University

• Uyeshima Makoto

  Earthquake Research Institute, The University of Tokyo

• Iio Yoshihisa

  National Research Institute for Earth Science and Disaster Prevention

• Uehara Daijiro

  Sumiko Consultants CO. LTD.

抄録

We carried out magnetotelluric measurements in the southeastern region of Mt. Ontake, where the 1984 Western Nagano Prefecture earthquake occurred and earthquake swarms have been observed since 1976. Most of the earthquakes have focal depths shallower than 10 km. The depth of the hypocenters increases towards the west. Our purpose is to delineate the resistivity structures down to the focal depths of the earthquakes, because the resistivity structure is very sensitive to the free water in the crust. The regional strike was estimated as N60°E. We carried out a two-dimensional analysis over two profiles across the earthquake fault of the 1984 Western Nagano Prefecture earthquake: one is in the low seismicity region of the fault (A-A′) and the other, in the high seismicity region (B-B′). The resistivity structure along the A-A′ profile is reasonably homogeneous and shows a high resistivity of more than 300 ohm-m. The resistivity structure along the B-B′ profile has a clear boundary at the center of the profile. This boundary divides the structure along the B-B′ profile into two resistivity blocks and its location coincides with that of the earthquake fault. A conductor is detected at depths greater than 8 km to the northwest of the earthquake fault. The depth to the upper boundary of the conductor coincides with those of the seismic reflectors. This structure seems to be formed by the free water dehydrated from the magma.

収録刊行物

• Ｅａｒｔｈ，　Ｐｌａｎｅｔｓ　ａｎｄ　Ｓｐａｃｅ

  Ｅａｒｔｈ，　Ｐｌａｎｅｔｓ　ａｎｄ　Ｓｐａｃｅ 54 (2), 107-118, 2002

  地球電磁気・地球惑星圏学会 、公益社団法人 日本地震学会、特定非営利活動法人 日本火山学会、日本測地学会、日本惑星科学会

キーワード

• Space and Planetary Science
• Geology

詳細情報

• CRID: 1390001206511645312
• NII論文ID: 10008634302
• NII論文ID: 130003780879
• NII書誌ID: AA11211921
• DOI: 10.1186/bf03351711
• ISSN: 18805981
• ISSN: 13438832
• NDL書誌ID: 6084040
• Web Site: https://ndlsearch.ndl.go.jp/books/R000000004-I6084040
• Web Site: https://link.springer.com/content/pdf/10.1186/BF03351711.pdf
• Web Site: https://link.springer.com/article/10.1186/BF03351711/fulltext.html
• Web Site: http://link.springer.com/content/pdf/10.1186/BF03351711
• 本文言語コード: en
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