THE RESPONSE OF WATER LEVEL IN THE YUZ-5 WELL, KAMCHATKA TO THE MAGNITUDE 9.3, SUMATRA-ANDAMAN EARTHQUAKE OF DECEMBER 26, 2004

Abstract

Forced and free oscillations of water level were recorded in the YuZ-5 well, Kamchatka due to the passage of seismic waves from the Sumatra-Andaman earthquake of December 26, 2004, M w = 9.3, hypocentral distance 8250 km. The greatest amplitude of water level oscillations, at least 5 cm, was observed during the onset of seismic surface waves with a typical period of 20–50 s. The total duration of the forced and free water level oscillations was about ten hours. The available theoretical models that describe oscillations of water level in a well due to seismic waves and rapid injection of water were used to estimate the transmissivity of the aquifer. The values obtained exceed by at least two orders of magnitude the transmissivity derived from pumping test measurements. A hypothesis was proposed to explain the temporary increase in aquifer transmissivity during the passage of seismic waves by invoking disturbances in the structure of the crack-pore space and a sharp increase in aquifer rock permeability.