Structural controls on the 1998 volcanic unrest at Iwate volcano

Relationship between a shallow, electrically resistive body and the possible ascent route of magmatic fluid

Koki Aizawa, Yasuo Ogawa, Masaaki Mishina, Kosuke Takahashi, Shintaro Nagaoka, Nobumasa Takagi, Shin'ya Sakanaka, Takuya Miura

研究成果: ジャーナルへの寄稿記事

14 引用 (Scopus)

抄録

Magnetotelluric (MT) measurements were conducted at Iwate volcano, across the entirety of the mountain, in 1997, 1999, 2003, 2006, and 2007. The survey line was 18 km in length and oriented E-W, comprising 38 measurements sites. Following 2D inversion, we obtained the resistivity structure to a depth of 4 km. The surface resistive layer (~ several hundreds of meters thick) is underlain by extensive highly conductive zones. Based on drilling data, the bottom of the highly conductive zone is interpreted to represent the 200 °C isotherm, below which (i.e., at higher temperatures) conductive clay minerals (smectite) are rare. The high conductivity is therefore mainly attributed to the presence of hydrothermally altered clay. The focus of this study is a resistive body beneath the Onigajo (West-Iwate) caldera at depths of 0.5-3 km. This body appears to have impeded magmatic fluid ascent during the 1998 volcanic unrest, as inferred from geodetic data. Both tectonic and low-frequency earthquakes are sparsely distributed throughout this resistive body. We interpret this resistive body as a zone of old, solidified intrusive magma with temperatures in excess of 200 °C. Given that a similar relationship between a resistive body and subsurface volcanic activity has been suggested for Asama volcano, structural controls on subsurface magmatic fluid movement may be a common phenomenon at shallow levels beneath volcanoes.

元の言語英語
ページ(範囲)131-139
ページ数9
ジャーナルJournal of Volcanology and Geothermal Research
187
発行部数1-2
DOI
出版物ステータス出版済み - 10 30 2009

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Volcanoes
structural control
ascent
volcanoes
volcanology
volcano
routes
Fluids
fluid
fluids
Magnetotellurics
geodetic datum
clays
Tectonics
Clay minerals
caldera
smectite
Isotherms
clay mineral
electrical resistivity

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Geochemistry and Petrology

これを引用

Structural controls on the 1998 volcanic unrest at Iwate volcano : Relationship between a shallow, electrically resistive body and the possible ascent route of magmatic fluid. / Aizawa, Koki; Ogawa, Yasuo; Mishina, Masaaki; Takahashi, Kosuke; Nagaoka, Shintaro; Takagi, Nobumasa; Sakanaka, Shin'ya; Miura, Takuya.

:: Journal of Volcanology and Geothermal Research, 巻 187, 番号 1-2, 30.10.2009, p. 131-139.

研究成果: ジャーナルへの寄稿記事

Aizawa, Koki ; Ogawa, Yasuo ; Mishina, Masaaki ; Takahashi, Kosuke ; Nagaoka, Shintaro ; Takagi, Nobumasa ; Sakanaka, Shin'ya ; Miura, Takuya. / Structural controls on the 1998 volcanic unrest at Iwate volcano : Relationship between a shallow, electrically resistive body and the possible ascent route of magmatic fluid. :: Journal of Volcanology and Geothermal Research. 2009 ; 巻 187, 番号 1-2. pp. 131-139.
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