[SVC47-P23] One-dimensional resistivity structure and the relocated hypocenter distribution of Iwo-yama, Kirishima Volcanoes
In order to investigate the mechanism of these volcanic activities and possibility of future eruptions, we conducted broadband (0.005 to 3000s) magnetotelluric (MT) measurements around the Iwo-yama in April 2016. We recorded two components of electric fields at 20 observation sites and five components of electric and magnetic fields at 7 observation sites. One-dimensional inversion revealed that the shallow earthquakes occur beneath a shallow electric conductive layer, which is interpreted as a hydrothermal altered clay dominant zone. The pressure source by the leveling survey corresponds to the bottom of the conductive layer. These spatial relationships suggest that the supply of high temperature fluids has increased beneath Iwo-yama, and causes the increase in pore pressure beneath clay layer, resulting in the increase of earthquakes and ground inflation. In this presentation, we will further estimate the precise depth of earthquakes, and will investigate its relation to the shallow conductive layer.