Frequency characteristics of the response of water pressure in a closed well to volumetric strain in the high-frequency domain

Abstract

Oscillations of water pressures and crustal strains due to the seismic waves of the 2010 Chile earthquake were observed in Japan. The oscillations of water pressures observed over the frequency range of 0.002 to 0.1 Hz were negative proportional to the oscillations of volumetric strains. The responses of water pressures in closed wells are frequency-dependent. The expression for the response of water pressure in a closed well to crustal strain is developed based on the poroelastic theory. The expression developed in the present paper describes the frequency characteristics of the responses. The response is useful for the estimation of rock properties. In addition, the responses of water pressure due to tidal volumetric strain are estimated and compared with the responses due to the seismic waves. Copyright 2011 by the American Geophysical Union.