Japan Geoscience Union Meeting 2018

Presentation information

[EJ] Oral

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

[S-CG57] Dynamics in mobile belts

Wed. May 23, 2018 1:45 PM - 3:15 PM A05 (Tokyo Bay Makuhari Hall)

convener:Yukitoshi Fukahata(Disaster Prevention Research Institute, Kyoto University), Toru Takeshita(Department of Natural History Sciences, Graduate School of Science, Hokkaido University), Hikaru Iwamori(海洋研究開発機構・地球内部物質循環研究分野), Chairperson:Muto Jun, Noda Akemi

1:45 PM - 2:00 PM

[SCG57-25] Kinematic history along the Hinagu fault zone, Kumamoto Prefecture, Kyushu, Japan

*Kenta Kobayashi1, Keiji Ogashiwa1, Keita Takahashi2, Shun Suzuki2, Yumeki Hoshika2, Naoki Takahashi1, Chihiro Takahashi1 (1.Department of Geology, Faculty of Science, Niigata University, 2.Graduate School of Science and Technology, Niigata University)

Keywords:Kumamoto Prefecture, Hinagu fault, active fault, fault rocks

The Hinagu fault zone was activated at the time of the 2016 Kumamoto earthquake. To understand how fault zone has developed over a long period of time, it is necessary to observe fault zone structures at the macro to microscope scales. We carried out field surveys in the NE-SW trending aftershock area of the earthquake, and analyzed the development of fractures and slip senses at the fault zone.

Brittle fault rock zones were distributed in the Higo metamorphic rocks (Permian-Triassic). NE-SW striking Y surfaces indicated sinistral (early stage) and dextral (late stage) slip senses. NE-SW striking remarkable brittle shear zone was also recognized in the Hinagu Formation (Early Cretaceous), indicated dextral slip sense. On the other hand, ENE-WSW trending fold structures adjacent to the east, indicated sinistral slip sense.

Viewed from the kinematics, the macroscale fault zone in the aftershock area has a long history of deformations. Parts of them were selected, and activated at the time of the 2016 Kumamoto earthquake.