Japan Geoscience Union Meeting 2016

Presentation information


Symbol M (Multidisciplinary and Interdisciplinary) » M-IS Intersection

[M-IS34] The 2016 Kumamoto Earthquake and related crustal activities

Thu. May 26, 2016 3:30 PM - 4:45 PM Poster Hall (International Exhibition Hall HALL6)

5:15 PM - 6:30 PM

[MIS34-P26] Broad-band magnetotelluric data around the focal region of the 2016 Kumamoto-Oita earthquakes

*Koki Aizawa1, Hisafumi Asaue2, Katsuaki Koike3, Shinichi Takakura4, Nobuo Matsushima4, Maki Hata4, Tohru yoshinaga5, Takeshi Hashimoto6, Mitsuru Utsugi7, Hiroyuki Inoue7, Taro Shiotani13, Makoto Uyeshima8, Takao Koyama8, Wataru Kanda9, Kazunari Uchida1, Yuko Tsukashima1, Azusa Shito1, Shiori Fujita12, Asuma Wakabayashi12, Kaori Tsukamoto12, Takeshi Matsushima1, Ryokei Yoshimura10, Ken'ichi Yamazaki10, Shintaro Komatsu10, Makoto Tamura11, The 2016 Kumamoto earthquake research group (1.Institute of Seismology and Volcanology, Faculty of Sciences, Kyushu University, 2.Laboratory on Innovative Techniques for Infrastructures, Kyoto University, 3.Graduate School of Engineering and Faculty of Engineering, Kyoto University, 4.National Institute of Advanced Industrial Science and Technology, 5.Kumamoto University, 6.Hokkaido University, 7.Kyoto University, 8.Earthquake Research Institute, University of Tokyo, 9.Volcanic Fluid Research Center, Tokyo Institute of Technology, 10.Disaster Prevention Research Institute, Kyoto University, 11.Hokkaido Research Organization, Geological Survery of Hokkaido, 12.Department of Earth and Planetary Sciences, Kyushu University, 13.Division of Earth and Planetary Sciences, Graduate School of Science, Kyoto University)

Keywords:resistivity structure, magnetotelluric data, The 2016 Kumamoto earthquake

The Mj 6.5 and Mj 7.3 Kumamoto earthquakes that occurred on 14 and 16 April 2016 triggered not only the aftershocks around the epicenters, but also triggered the earthquakes 50~100 km far from the main shocks. The aftershocks and the triggered earthquakes that exceed Mj 3.5 are amounted up 230 on 8 May, 2016, and are mainly located on NE-SW lines that may correspond to the westward extension of median tectonic line (MTL). The active seismicity can be divided into three regions, (1) the Futagawa and Hinagu faults (the region around the main shocks), (2) the northern part of Aso volcano, and (3) the region around the Tsurumi and Yufu volcanoes. There are distinct seismically inactive area between these regions. We show the broad-band (200~0.0003 Hz) MT data, which were obtained 1999~2015 around these focal regions. The dataset consists of that around the main shocks (Asaue et al., 2006, 2013; Takakura et al., 2000; Hata et al., 2016), and that around the triggered seismicity (Aizawa et al., 2015, 2016; Shiotani et al., 2015). The apparent resistivity of the sum of the squared elements (ssq) invariant impedance (Rung-Arunwan et al., 2016) shows that the earthquakes occur on the electric resistive zones. The electric conductive zones correspond to the seismically inactive areas. The faults of main shock is located at the boundary between conductive and resistive zones. We will discuss the possibility that the series of earthquakes were guided by the resistivity structure.

The figures is found below.

This work is partly supported by MEXT KAKENHI Grant Number 16H06298, MEXT under its Earthquake and Volcano Hazards Observation and Research Program, and
Earthquake Research Institute, University of Tokyo under Joint Usage Program.

Asaue, H., Koike, K., Yoshinaga, T., and Takakura, S., 2006, Magnetotelluric resistivity modeling for 3D characterization of geothermal reservoirs in the Western side of Mt. Aso, SW Japan: Journal of Applied Geophysics, v. 58, p. 296-312.
Asaue, H., Kubo, T., Yoshinaga, T., and Koike, K., 2012, Application of Magnetotelluric (MT) Resistivity to Imaging of Regional Three-Dimensional Geologic Structures and Groundwater Systems: Natural Resources Research, v. 21, p. 383-393.
Rung-Arunwan, T., Siripunvaraporn, W., and Utada, H., 2016, On the Berdichevsky average: Physics of the Earth and Planetary Interiors, v. 253, p. 1-4.