GP006-07
Hydrothermal and magmatic plumbing system of Miyakejima volcano (Japan) inferred from magnetotellurics, seismicity, self-potential and thermal image
Tuesday, 15 December 2020: 04:44
Virtual
Marceau Gresse1, Makoto Uyeshima1, Takao Koyama1, Hideaki Hase2, Koki Aizawa3, Yusuke Yamaya4, Yuichi Morita5, Derek Weller5, Tawat Rung-Arunwan6, Takayuki Kaneko1, Yoichi Sasai7, Jacques Zlotnicki8, Tsuneo Ishido9, Hideki Ueda10 and Maki Hata1, (1)Earthquake Research Institute (ERI), University of Tokyo, Tokyo, Japan, (2)Geothermal Energy Research & Development Co., Ltd., Tokyo, Japan, (3)Kyushu University, Fukuoka, Japan, (4)National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan, (5)Earthquake Research Institute, University of Tokyo, Tokyo, Japan, (6)Curl-E Geophysics Co., Ltd., Bangkok, Thailand, (7)Earthquake Prediction Research Center, Tokai University, Shizuoka, Japan, (8)French National Centre for Scientific Research (CNRS), Aubière, France, (9)Geological Survey Japan, AIST, Tsukuba, Japan, (10)National Research Institute for Earth Science and Disaster Resilience (NIED), Tsukuba, Japan
Abstract:
Miyakejima is a basaltic-andesitic stratovolcano (10 km wide, 775 a.s.l.) located in the Pacific Ocean, 180 km to the south of Tokyo, in the Izu-Bonin volcanic arc. Active volcanic islands are well-known to develop extensive hydrothermal systems due to intense rainfall and seawater intrusion which induces high and regular volcanic-hazards (e.g. Miyakejima phreato-magmatic eruption in 2000, White Island phreatic eruption in 2016, 2019).
In order to better assess the role of hydrothermal systems and their connection with the hydrosphere and the underlying magmatic system, we present here the first electrical conductivity model of Miyakejima Island obtained from 13 broadband magnetotelluric stations deployed in 2012. By combining the electrical conductivity model with hypocenters distributions, together with infrared thermal image and self-potential mappings, we precisely highlight the plumbing system of the volcano: magmatic fluids originating from a deep resistive region (>2.5 km depth, 50-100 Ωm), rise through a narrow path, interact with the shallow conductive hydrothermal system (0-1 km depth, 1-20 Ωm) before finally being released in the main fumarolic area inside the caldera. The “W” shaped self-potential signal precisely reveals the shallow fluid-flow circulation within the volcanic edifice that is linked with geological and tectonic features. In particular, a positive anomaly delineates a shallow conductive region spatially associated with vent locations of the1983 eruption.
