TY - JOUR
T1 - Seismicity controlled by resistivity structure
T2 - The 2016 Kumamoto earthquakes, Kyushu Island, Japan
AU - Aizawa, Koki
AU - Asaue, Hisafumi
AU - Koike, Katsuaki
AU - Takakura, Shinichi
AU - Utsugi, Mitsuru
AU - Inoue, Hiroyuki
AU - Yoshimura, Ryokei
AU - Yamazaki, Ken'Ichi
AU - Komatsu, Shintaro
AU - Uyeshima, Makoto
AU - Koyama, Takao
AU - Kanda, Wataru
AU - Shiotani, Taro
AU - Matsushima, Nobuo
AU - Hata, Maki
AU - Yoshinaga, Tohru
AU - Uchida, Kazunari
AU - Tsukashima, Yuko
AU - Shito, Azusa
AU - Fujita, Shiori
AU - Wakabayashi, Asuma
AU - Tsukamoto, Kaori
AU - Matsushima, Takeshi
AU - Miyazaki, Masahiro
AU - Kondo, Kentaro
AU - Takashima, Kanade
AU - Hashimoto, Takeshi
AU - Tamura, Makoto
AU - Matsumoto, Satoshi
AU - Yamashita, Yusuke
AU - Nakamoto, Manami
AU - Shimizu, Hiroshi
N1 - Funding Information:
We are greatly indebted to the landowners for permitting access for field campaigns. The geomagnetic data used for the remote-reference processing were provided by the Kakioka Geomagnetic Observatory of the Japan Meteorological Agency and Esashi Observatory of the Geospatial Information Authority of Japan. Our gratitude goes to S. Constable for supplying his 1-D inversion code. We thank the students of Kyushu University for their assistance during the field campaigns. Comments by two anonymous reviewers and the Associate Editor, M. Hashimoto, greatly improved the manuscript. This study was supported by the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan, under its “Earthquake and Volcano Hazards Observation and Research Program” and “Research on Active faults surveys” by the Headquarters for Earthquake Research Promotion. Observations for seismic data were 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.
Publisher Copyright:
© 2017 The Author(s).
PY - 2017/12/1
Y1 - 2017/12/1
N2 - 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.]
AB - 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.]
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U2 - 10.1186/s40623-016-0590-2
DO - 10.1186/s40623-016-0590-2
M3 - Article
AN - SCOPUS:85008413160
VL - 69
JO - Earth, Planets and Space
JF - Earth, Planets and Space
SN - 1343-8832
IS - 1
M1 - 4
ER -