Japan Geoscience Union Meeting 2018

Presentation information

[JJ] Oral

A (Atmospheric and Hydrospheric Sciences) » A-HW Hydrology & Water Environment

[A-HW24] Hydrological change after the 2016 Kumamoto earthquake

Tue. May 22, 2018 1:45 PM - 3:15 PM A02 (Tokyo Bay Makuhari Hall)

convener:Jun Shimada(Graduate school of Science and Technology, Kumamoto University), Kei Nakagawa(Graduate School of Fisheries Science and Environmental Studies, Nagasaki University), Takahiro Hosono(熊本大学大学院先導機構, 共同), Takeshi Hayashi(Faculty of Education and Human Studies, Akita University), Chairperson:Hosono Takahiro(熊本大学先導機構), Nakagawa Kei(長崎大学大学院環境科学研究科)

2:30 PM - 2:45 PM

[AHW24-04] Coseismic change in groundwater level after the 2016 Kumamoto earthquake

*Takahiro Hosono1, Chisato Yamada2, Tomo Shibata3, Yasuhiro Tawara4, Jun Shimada1 (1.Priority Organization for Innovation and Excellence, Kumamoto University, 2.Department of Earth Science, Faculty of Science, Kumamoto University, 3.Institute for Geothermal Sciences, Kyoto University, 4.Geosphere Environmental Technology Corporation)

Keywords:Kumamoto earthquake, Groundwater flow system, Groundwater level change, Crustal ruptures

Opportunities to observe coseismic hydrological changes in generation of new fault systems are rare. We provide direct evidence of significant groundwater drawdowns (4.65 m maximum over a 160 km2 area) along crustal ruptures associated with the 2016 Kumamoto earthquake using extensive high-resolution water level monitoring records. In the localized fault area, approximately 106 m3 of groundwater was transferred into crustal ruptures extending to a depth of ~5 km. The groundwater filled open cracks within 35 minutes after the shock to compensate for the vacuum pressure generated in the deep opening in the crust. There was no evidence of a coseismic surface water response to offset the loss of groundwater. Observed water drawdown should be considered an important mechanism of coseismic hydrological change. In this presentation we will report comprehensive coseismic groundwater level change mechanism after the 2016 Kumamoto earthquake.