Japan Geoscience Union Meeting 2018

Presentation information

[EJ] Oral

S (Solid Earth Sciences) » S-SS Seismology

[S-SS08] Active faults and paleoseismology

Tue. May 22, 2018 9:00 AM - 10:30 AM A07 (Tokyo Bay Makuhari Hall)

convener:Mamoru Koarai(Earth Science course, College of Science, Ibaraki University), Hisao Kondo(Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology), Ryosuke Doke(神奈川県温泉地学研究所, 共同), Nobuhisa Matsuta(Okayama University Graduate School of Education), Chairperson:MATSUTA NOBUHISA(Okayama University), Une Hiroshi

9:15 AM - 9:30 AM

[SSS08-08] How generated the cracks in the Aso valley, Japan, caused by the 2016 Kumamoto earthquake?

*Tsuyoshi Haraguchi1, Hisao Hayashi2, Yuichi Yoshoinaga3 (1.Department of Geosciences,Graduate School of Science,Osaka City University, 2.Geo-X Consultants Corporation, 3.Disaster Prevention Geo-Research Institute)

Keywords:2016 Kumamoto earthquake, crack, Lateral-spread graben

Many cracks generated by the 2016 Kumamoto earthquake appeared in the Aso Valley. It can be classified into two types from the origin. One is a crack group of backfill traces such as old river channel and mining areas. Example of Yakuinbaru area is a typical one. It showed displacement along the old riparian line due to subsidence and slip. Another collapse crack appeared in Uchinomaki, Kario and Matoishi. The S wave structure up to hundreds of meters underground was determined by the representative line, confirming the geologic structure leaning loosely to the north. At the time of the earthquake the ground up to the depth of about 60 m underground moved to the north. It ranged from 1 to 2 km per square. The cause of the crack group is Lateral-spread graben generated in the tension part of the moving region. Joined the subsidence of mining ruins in Matoishi area, it was expanded further displacement.