Groundwater flow and hydrothermal systems within volcanic edifices: Delineation by electric self-potential and magnetotellurics

Koki Aizawa, Yasuo Ogawa, Tsuneo Ishido

研究成果: Contribution to journalArticle査読

67 被引用数 (Scopus)

抄録

The imaging of hydrotherinal systems within volcanoes is critical in evaluating the nature and likelihood of future volcanic activity and hazard assessment. In this study, we present a conceptual model of the hydrothertnal system in a volcanic edifice, as deduced from the relationship between electric self-potential (SP) and high-resolution resistivity structures. In order to develop a comprehensive model of water flow in volcanoes, we conducted the audiofrequency (10,000-0.3 Hz) magnetotelluric surveys in five large stratovolcanoes (Iwate, Iwaki, Nasu, Nantai, and Nikko-Shirane) in Japan and found that the obtained 2-D resistivity profiles have a close relationship to the previously reported SP data: good extensive conductors occur beneath areas without SP anomalies, whereas good localized conductors only occur beneath large spatial wavelength SP anomalies on the volcano side of the SP minimum. Also taking into account the locations of surface geothermal activity, the good conductors roughly correspond to the hydrothermal zone, whose upper limit is sealed by a low-permeability clay layer. The sealing layer separates an upper groundwater flow from a lower hydrothermal flow in the subsurface and controls the geothennal manifestations and river locations on the surface. We confirmed the feasibility of the proposed model based on numerical simulations of a hydrothermal system. The horizontal extent of the hydrothermal zone is highly heterogeneous even in a volcanic edifice. This heterogeneity can reflect the geological age of flanks that may be related to the occurrence of a previous large sector collapse.

本文言語英語
論文番号B01208
ジャーナルJournal of Geophysical Research: Solid Earth
114
1
DOI
出版ステータス出版済み - 1 4 2009
外部発表はい

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Geochemistry and Petrology
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science

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