JpGU-AGU Joint Meeting 2017

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[JJ] Oral

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

[S-CG75] [JJ] Crustal fluids and deformation

Sun. May 21, 2017 1:45 PM - 3:15 PM 106 (International Conference Hall 1F)

convener:Naoji Koizumi(School of Environmental Science,the University of Shiga Prefecture), Koji Umeda(Hirosaki University), 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), Chairperson:KOJI UMEDA(Hirosaki University), Chairperson:NAOJI KOIZUMI(School of Environmental Science,the University of Shiga Prefecture)

2:45 PM - 3:00 PM

[SCG75-05] Crustal resistivity structure beneath the source region of 2014 northern Nagano earthquake

*Koichi Asamori1, Yuki Hama1, Koji Umeda2, Hidemi Tanaka3 (1.Japan Atomic Energy Agency, 2.Hirosaki Univ., 3.Univ. of Tokyo)

Keywords:2014 northern Nagano earthquake, resistivity structure, crustal fluids

In this study we have determined two dimensional (2-D) resistivity structure beneath the source region of 2014 northern Nagano earthquake. Seventeen 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 (400 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]. The obtained resistivity model through the inversion show as follows: (1) The mainshock hypocenter is located in a prominent conductive zone. (2) This anomaly is imaged in the depth range of 3 to 20 km. (3) These results indicate that the conductive zone may be due to crustal fluids that contributed to the occurrence of the large earthquake.