Changes in Widespread Aquifer Properties caused by a Magnitude 6 Class Earthquake evaluated using InSAR Analyses

Abstract

The correlation between surface displacements and groundwater level changes has been widely used to understand aquifer properties and their site characteristics; however, the underlying mechanism of various correlation types and influence of earthquakes has not been fully investigated. In this study, we examine correlations in Osaka and Kyoto, Japan, over 4 years including the period of the June 18, 2018, Mw 5.6 northern Osaka earthquake surface displacement from InSAR analyses and groundwater level monitoring data. Both positive and negative correlations were identified at groundwater level observation stations. Based on the different types of correlations, we propose a new conceptual aquifer model that drives the opposite interaction between the surface displacement and the groundwater level change. 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.