open access

https://doi.org/10.14943/gbhu.73.281

https://hdl.handle.net/2115/44482

Three-dimensional resistivity structure around the 62-II crater at Tokachidake volcano

日本語

2010-03-19

北海道大学大学院理学研究院自然史科学部門（地球物理学）

Geophysical bulletin of Hokkaido University

73

281-294

Tokachidake Volcano is an active volcano, situated at the SW end of the Daisetsu-Tokachi volcanic chain in the central Hokkaido, Japan. We performed the AMT resistivity survey around the 62 -II crater at the volcano in order to realize the hydrothermal zone, focusing on the recent activity of the crustal inflation and demagnetization beneath the crater. The measured AMT data suggested the three-dimensional structure beneath the study area. Prior to the resistivity modeling, we estimated an effect due to a steep topography in the study area. This estimation clearly showed a strong effect to the apparent resistivity, impedance phase and induction vector. Therefore, the simplified topography was included to the three-dimensional model. The resistivity model supposed by a forward modeling was characterized by a conductor （0.5Ωm） beneath the 62-II crater. We investigated a physical condition which could bring the resistivity of 0.5Ωm, and then estimated that high porosity （0.3）rocks were saturated with hot（～200℃）pore water including dissolved components. Although the origin of hydrothermal water has been unresolved, this result suggests that a hydrothermal zone is developed beneath the 62-II crater.

紀要論文

Version of Record

0439-3503

AN0008976X