Stable isotopes show that earthquakes enhance permeability and release water from mountains

This study investigates the hydrogeological changes in response to large crustal earthquakes, focusing on permeability increase and coseismic changes in groundwater level and flow. Using a large dataset of water stable isotope ratios (n=1150), the researchers demonstrate that newly formed rupture systems from the 2016 M_w 7.0 Kumamoto earthquake crosscut mountain aquifers, leading to water release and a subsequent groundwater level rise (~11 m) in down-gradient aquifers. The study rules out vertical infiltration and deep fluid upwelling as the primary causes, suggesting the observed changes are due to enhanced permeability. Given the Kumamoto setting's representativeness of volcanic aquifer systems in seismotectonic areas, the findings have broader implications for understanding earthquake impacts on hydrology.

Takahiro Hosono, Chisato Yamada, Michael Manga, Chi-Yuen Wang, Masaharu Tanimizu