Abstract
Frequency response of water level fluctuation to seismic wave was determined at a confined water well in the Izu Peninsula, Japan. The purpose of this study is to detect the enhancement of hydraulic conductivity of the aquifer in this area that was suggested associated with nearby seismic swarm activity due to removal of deposits in the aquifer caused by strong seismic motion. In the analysis, depression in the peak value of the response function of water level to seismic wave was found as the amplitude of seismic wave increases. The observed depression was explained by the theoretical estimate of the depression due to friction associated with the water movement as a turbulent flow in the pipe of the well. After correcting this dependency, temporal variation in the response function was investigated. However, expected increase of the response function associated with the seismic swarm activities was not detected. The response function showed a decreasing trend with time, although the variation did not exceed the estimated errors; this trend is interpreted by decreasing hydraulic conductivity due to formation of barrier by deposition in the aquifer.
