Three-dimensional resistivity structure of Asama Volcano revealed by data-space magnetotelluric inversion using unstructured tetrahedral elements

Yoshiya Usui, Yasuo Ogawa, Koki Aizawa, Wataru Kanda, Takeshi Hashimoto, Takao Koyama, Yusuke Yamaya, Tsuneomi Kagiyama

研究成果: ジャーナルへの寄稿記事

11 引用 (Scopus)

抄録

Asama Volcano is an andesitic composite volcano and one of the most active volcanoes in Japan. In order to reveal electrical resistivity structure beneath the volcano accurately, we performed a 3-D inversion of dense magnetotelluric survey data. In order to prevent misinterpretation of the subsurface resistivity due to the steep topography around Asama Volcano, we used an unstructured tetrahedral mesh to represent the topography. Furthermore, we reduced the calculation time by transforming the inverse problem from the model space into the data space. Comparison of the new data-space method to the original model-space method showed that the calculation time required to update the model parameterswas reduced as a result of the transformation, whereas the resistivity structure obtained remained unchanged. In the subsurface resistivity structure around Asama Volcano that was estimated from the inversion, resistive bodies were discovered to be located under the old eruption centres. In particular, under the 24 ka collapse caldera to the west of the presently active crater, a spherical resistive body was found to exist in isolation. In addition, there was a widespread conductive layer below the resistive surface layer. By comparison with previous hydrological and geochemical studies, the conductive layer was interpreted as being a high-water-content layer and an overlying layer rich in altered clay minerals. Because the western part of the volcanic conduit was considered to be the resistive area, which is inferred to consist of unfractured rocks with lower permeability than their surroundings, it would appear that the area obstructs the westward flow of the hydrothermal fluid beneath the summit, thereby contributing to higher concentrations of SO4 2- and Cl- in the spring water at the northern and eastern feet as well as the uneven location of a diffuse CO2 anomaly.

元の言語英語
ページ(範囲)1359-1372
ページ数14
ジャーナルGeophysical Journal International
208
発行部数3
DOI
出版物ステータス出版済み - 1 1 2017

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Magnetotellurics
Volcanoes
volcanoes
electrical resistivity
volcano
inversions
Topography
topography
springs (water)
stratovolcano
spring water
inverse problem
Springs (water)
hydrothermal fluid
caldera
calderas
crater
clay mineral
Clay minerals
surface layer

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Geochemistry and Petrology

これを引用

Three-dimensional resistivity structure of Asama Volcano revealed by data-space magnetotelluric inversion using unstructured tetrahedral elements. / Usui, Yoshiya; Ogawa, Yasuo; Aizawa, Koki; Kanda, Wataru; Hashimoto, Takeshi; Koyama, Takao; Yamaya, Yusuke; Kagiyama, Tsuneomi.

:: Geophysical Journal International, 巻 208, 番号 3, 01.01.2017, p. 1359-1372.

研究成果: ジャーナルへの寄稿記事

Usui, Yoshiya ; Ogawa, Yasuo ; Aizawa, Koki ; Kanda, Wataru ; Hashimoto, Takeshi ; Koyama, Takao ; Yamaya, Yusuke ; Kagiyama, Tsuneomi. / Three-dimensional resistivity structure of Asama Volcano revealed by data-space magnetotelluric inversion using unstructured tetrahedral elements. :: Geophysical Journal International. 2017 ; 巻 208, 番号 3. pp. 1359-1372.
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AU - Kanda, Wataru

AU - Hashimoto, Takeshi

AU - Koyama, Takao

AU - Yamaya, Yusuke

AU - Kagiyama, Tsuneomi

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