Hydrological response to earthquakes in the Haibara well, central Japan - II. Possible mechanism inferred from time-varying hydraulic properties

• DOI: 10.1111/j.1365-246x.2003.02104.x
• Publication Date: 2003-11-25T19:56:23Z
• Authors: N. Matsumoto; E. A. Roeloffs
• Keywords: 13. Climate action; 01 natural sciences; 6. Clean water; 0105 earth and related environmental sciences

28 coseismic groundwater level decreases have been observed at the Haibara well, Shizuoka prefecture, central Japan, from 1981 to 1997. These changes cannot be explained as poroelastic response static strain. We use atmospheric pressure and tidal responses of rock properties measured on core samples same formation pumping test results characterize hydraulic mechanical aquifer. The well M2 Earth tide constituent varied over time. In particular, increasing amplitude decreasing phase lags were after 1993 test, earthquakes that caused water changes. response, together with surface load efficiency derived is used estimate largest constituent, 2.2 mm, small enough imply pore fluid in this system approximately twice compressible water, possibly due presence a amount exsolved gas. Diffusion drop near could account for time histories drops are matched by decay least 80 m away well. Removal gas location might turn explain drops.