Seismicity controlled by resistivity structure: The 2016 Kumamoto earthquakes, Kyushu Island, Japan

Koki Aizawa, Hisafumi Asaue, Katsuaki Koike, Shinichi Takakura, Mitsuru Utsugi, Hiroyuki Inoue, Ryokei Yoshimura, Ken'Ichi Yamazaki, Shintaro Komatsu, Makoto Uyeshima, Takao Koyama, Wataru Kanda, Taro Shiotani, Nobuo Matsushima, Maki Hata, Tohru Yoshinaga, Kazunari Uchida, Yuko Tsukashima, Azusa Shito, Shiori FujitaAsuma Wakabayashi, Kaori Tsukamoto, Takeshi Matsushima, Masahiro Miyazaki, Kentaro Kondo, Kanade Takashima, Takeshi Hashimoto, Makoto Tamura, Satoshi Matsumoto, Yusuke Yamashita, Manami Nakamoto, Hiroshi Shimizu

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11 Citations (Scopus)

Abstract

The M JMA 7.3 Kumamoto earthquake that occurred at 1:25 JST on April 16, 2016, not only triggered aftershocks in the vicinity of the epicenter, but also triggered earthquakes that were 50-100 km away from the epicenter of the main shock. The active seismicity can be divided into three regions: (1) the vicinity of the main faults, (2) the northern region of Aso volcano (50 km northeast of the mainshock epicenter), and (3) the regions around three volcanoes, Yufu, Tsurumi, and Garan (100 km northeast of the mainshock epicenter). Notably, the zones between these regions are distinctively seismically inactive. The electric resistivity structure estimated from one-dimensional analysis of the 247 broadband (0.005-3000 s) magnetotelluric and telluric observation sites clearly shows that the earthquakes occurred in resistive regions adjacent to conductive zones or resistive-conductive transition zones. In contrast, seismicity is quite low in electrically conductive zones, which are interpreted as regions of connected fluids. We suggest that the series of the earthquakes was induced by a local accumulated stress and/or fluid supply from conductive zones. Because the relationship between the earthquakes and the resistivity structure is consistent with previous studies, seismic hazard assessment generally can be improved by taking into account the resistivity structure. Following on from the 2016 Kumamoto earthquake series, we suggest that there are two zones that have a relatively high potential of earthquake generation along the western extension of the MTL. [Figure not available: see fulltext.]

Original languageEnglish
Article number4
Journalearth, planets and space
Volume69
Issue number1
DOIs
Publication statusPublished - Dec 1 2017

All Science Journal Classification (ASJC) codes

  • Geology
  • Space and Planetary Science

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    Aizawa, K., Asaue, H., Koike, K., Takakura, S., Utsugi, M., Inoue, H., Yoshimura, R., Yamazaki, KI., Komatsu, S., Uyeshima, M., Koyama, T., Kanda, W., Shiotani, T., Matsushima, N., Hata, M., Yoshinaga, T., Uchida, K., Tsukashima, Y., Shito, A., ... Shimizu, H. (2017). Seismicity controlled by resistivity structure: The 2016 Kumamoto earthquakes, Kyushu Island, Japan. earth, planets and space, 69(1), [4]. https://doi.org/10.1186/s40623-016-0590-2