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-P44] Surface Fault Ruptures of the 2016 Kumamoto Earthquake

*Hideaki Goto1, Yasuhiro Kumahara1, Takashi Nakata1, Satoshi Ishiguro2, Daisuke Ishimura3, Tatsuya Ishiyama4, Shinsuke Okada5, Kyoko Kagohara6, kashihara shintaro7, Heitaro Kaneda7, Nobuhiko Sugito8, Yasuhiro Suzuki9, Daishi Takenami10, Kei Tanaka11, Tomoki Tanaka7, Hiroyuki Tsutsumi12, Shinji Toda5, Daisuke Hirouchi13, Nobuhisa Matsuta10, Hikaru Moriki10, Haruka Yoshida14, Mitsuhisa Watanabe15 (1.Hiroshima University, 2.Aichi Institute of Technology, 3.Tokyo Metropolitan University, 4.University of Tokyo, 5.Tohoku University, 6.Yamaguchi University, 7.Chiba University, 8.Hosei University, 9.Nagoya University, 10.Okayama University, 11.Japan Map Center, 12.Kyoto University, 13.Shinshu University, 14.Fukuoka Prefectural Yame High School, 15.Toyo University)

Keywords:2018 Kumamoto Earthquake, earthquake fault, active fault

A Mj 6.5 earthquake hit Kumamoto prefecture, central Kyushu, southwest Japan at 21:26 JST on April 14th. 28 hours after, another Mj 7.3 at 01:25 JST on April 16 generated severe shaking in the same region (JMA, 2016). It is well know previously mapped the ~100-km-long active fault called Futagawa-Hinagu fault zone (FHFZ) (Watanabe et al., 1979; RGATK, 1989; Ikeda et al., 2001; Nakata and Imaizumi ed, 2002) runs in the epicentral area, we considered the northeastern portion of the FHFZ could be responsible to two earthquakes and started to do a field reconnaissance along the fault zone after the Mj 6.5 event.
According to 3 weeks field survey by our team, we found the 31-km-length successive surface rupture close to the traces of the northeastern portion of the FHFZ and another the 5-km-length rupture on a part of Denokuchi fault and some possible surface ruptures in the epicentral area. The rupture along the FHFZ shows right-lateral strike-slip mainly (~ 2 m in maximum between Dozon in Mashiki city and Nishihara village) with down-thrown to northwest. The rupture on the Denokuchi fault, far from 1 to 2km east of the FHFZ, is normal component with down to northwest. These coseismic ruptures of the Mj 7.3 earthquake represented a characteristic movement of the northeastern portion of the FHFZ.
A series of the open cracks with NW-SE-trending were traceable for a distance of 5.4 km from Kengun to Shirakawa River in Kumamoto city. Those features followed on tectonic landform by possible active fault and on the line of the fringe abnormal in InSAR image, and may represent minor surface rupture.
The local eyewitness and our observation revealed that the coseismic minor rupture of the Mj 6.5 earthquake prior to the Mj 7.3 earthquake were emerged on the some trace of the rupture of the Mj 7.3 earthquake in Mifune town and South of Mashiki town.