Japan Geoscience Union Meeting 2016

Presentation information

Oral

Symbol S (Solid Earth Sciences) » S-CG Complex & General

[S-CG60] Crustal fluids and deformation

Tue. May 24, 2016 10:45 AM - 12:15 PM A05 (APA HOTEL&RESORT TOKYO BAY MAKUHARI)

Convener:*Naoji Koizumi(School of Environmental Science,the University of Shiga Prefecture), Koji Umeda(Tono Geoscience Center,Japan Atomic Energy Agency), Norio Matsumoto(Tectono-Hydrology Research Group, Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology (AIST)), Hidemi Tanaka(School of Science, The University of Tokyo), Kohei Kazahaya(Geological Survey of Japan, AIST), Fumiaki Tsunomori(Geochemical Research Center, Graduate School of Science, University of Tokyo), Chair:Naoji Koizumi(School of Environmental Science,the University of Shiga Prefecture), Fumiaki Tsunomori(Geochemical Research Center, Graduate School of Science, University of Tokyo)

10:45 AM - 11:00 AM

[SCG60-01] Crustal fluids beneath Kyushu forearc region

*Koichi Asamori1, Yuki Hama1, Koji Umeda1 (1.Japan Atomic Energy Agency)

In this study we have determined two dimensional (2-D) resistivity and three dimensional (3-D) seismic velocity structure beneath Kyushu subduction zone. 40 magnetotelluric (MT) stations were deployed in the study area. The MT data were collected using five component wide-band MT instruments (Phoenix MTU-5 system). A simultaneous remote reference measurement was carried out at the Sawauchi site (900 km northeast of the study area). The observed apparent resistivity and phase data were inverted simultaneously using the 2-D inversion code of Ogawa and Uchida [1996]. We have applied a tomographic method [Zhao et al., 1994] to P and S arrival times from regional earthquakes and teleseismic events to determine a detailed 3-D P and S wave velocity structure beneath Kyushu. The obtained resistivity and seismic velocity model through the inversions show as follows: (1) In central Kyushu, a prominent conductive anomaly exists in the crust beneath the forearc region. (2) A low-velocity zone corresponding to the conductive anomaly was revealed in the crust. (3) These results indicate that the conductive and low-velocity zone may reflect crustal fluids in the forearc region.