Changes in widespread aquifer properties caused by a magnitude 6-class earthquake evaluated using InSAR analyses

Correlations between surface displacements and groundwater level changes have been widely used to understand aquifer properties and their site characteristics; however, the underlying mechanisms of various correlation types and the influence of earthquakes have not been fully investigated. In this study, we examine correlations between surface displacements from interferometric synthetic aperture radar analyses and groundwater level monitoring data in Osaka and Kyoto, Japan, over 4 years, a period including the 18 June 2018 Mw 5.6 northern Osaka earthquake. Both positive and negative correlations between the seasonal groundwater level changes and the seasonal surface displacements are identified. Based on the observations of the effects of the earthquake, a new conceptual aquifer dynamical model driving the relationship between the surface displacements and the groundwater level changes is proposed. We further reveal that sites with negative correlations increased after the earthquake, suggesting that the earthquake increased the groundwater recharge rate as a result of increases in aquifer transportation properties such as permeability and porosity.