Japan Geoscience Union Meeting 2015

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

[S-CG57] Structure, evolution and dynamics of mobile belts

Thu. May 28, 2015 9:00 AM - 10:45 AM IC (2F)

Convener:*Toru Takeshita(Department of Natural History Sciences, Graduate School of Science, Hokkaido University), Hiroshi Sato(Earthquake Prediction Research Center, Earthquake Research Institute, The University of Tokyo), Koichiro Obana(Research and Development Center for Earthquake and Tsunami, Japan Agency for Marine-Earth Science and Technology), Takuya NISHIMURA(Disaster Prevention Research Institute, Kyoto University), Yukitoshi Fukahata(Disaster Prevention Research Institute, Kyoto University), Aitaro Kato(Graduate School of Environmental Studies, Nagoya University), Jun Muto(Department of Earth Sciences, Tohoku University), Katsushi Sato(Division of Earth and Planetary Sciences, Graduate School of Science, Kyoto University), Shuichi Kodaira(Institute for Research on Earth Evolution Japan Agency for Marine-Earth Science and Technology), Takeshi Sagiya(Disaster Mitigation Research Center, Nagoya University), Tatsuya Ishiyama(Earthquake Research Institute, University of Tokyo), Makoto MATSUBARA(National Research Institute for Earth Science and Disaster Prevention), Yasutaka Ikeda(Department of Earth and Planetary Science, Graduate School of Science, University of Tokyo), Chair:Tadashi Yamasaki(National Institute of Advanced Industrial Science and Technology)

9:30 AM - 9:45 AM

[SCG57-12] 3D Resistivity Structure around the Epicenter of Iwate-Miyagi Nairiku Earthquake and Crustal Deformations

*Atsushi SUZUKI1, Yasuo OGAWA2, Zenshiro SAITO1, Masashi USHIODA2 (1.Department of earth and Planetary Sciences, Tokyo Institute of Technology, 2.Volcanic Fluid Research Center, Tokyo Institute of Technology)

Keywords:Iwate-Miyagi Nairiku Earthquake, resistivity structure, magnetotellurics, fluid, deformation, post seismic deformation

The 2008 Iwate-Miyagi Nairiku Earthquake (M 7.2) was an unusually large earthquake, which occurred near the volcanic regions. To understand the mechanism of inland earthquakes, it is important to study the structure around the area. Okada et al. (2012) observed aftershocks precisely and estimated the seismic velocity structure. Iinuma et al. (2009) detected coseismic and aseismic slips with GPS observations. Mishina (2009) and Ichihara et al. (2014) conducted 2-D and 3-D MT surveys respectively. However, the MT station distributions of the previous MT surveys were sparse. We carried out denser surveys and showed more precise resistivity structures around the area. We conducted MT surveys at 66 stations (59 stations from October until November in 2012 and 7 stations from October until November in 2014) around the area and estimated 3-D resistivity structures using inversion code of Siripunvaraporn and Egbert (2009) with full impedance tensor as response functions. The result of our final resistivity structures is similar to the one in Ichihara et al. (2014), but is more complex. We found a low resistivity zone to the northeast of Mt. Kurikoma below 3km depth. This anomaly is connected with a low resistivity zone located under Mt. Kurikoma below 10km depth. The locations of aseismic and co-seismic slips in Iinuma et al. (2009) correspond to the locations of low resistivity and high resistivity zones in our model respectively. This may represent that low resistivity zones are brittle and high resistivity zones are ductile.