Coseismic Radon Changes of e 1995 Hyogo-ken Nanbu Earthquake

Abstract

This article reports a preliminary result of seismic-related radon changes in groundwater observed at a continuous monitoring station in the Tokai district. Immediately after the M7.2 Hyogo-ken Nanbu earthquake which occurred on January 17, 1995, the radon concentration of a water well at a hypocentral distance of 260 km decreased by about 5%. It is meaningful that a drop in the radon concentration was observed, while the water level showed no significant change.