Water-Level Changes in the Wells of Kamchatka at the Time of the Mw 7.6, April 20, 2006 Olyutorskii Earthquake

Abstract

The seismic waves excited by the Mw 7.6 Olyutorskii earthquake that occurred on April 20, 2006 in the Koryak Upland gave rise to water-level changes in five wells situated in continental areas of Kamchatka at hypocentral distances of 750–1150 km. We describe the effects due to seismic waves, as well as the water-level anomalies for February–April 2006 before the earthquake. We used an original technique for the processing of water-level records based on the study of barometric and tidal water-level responses in order to estimate the volume strain in water-saturated rocks during synchronous level variations at two wells. We discuss possible mechanisms for producing anomalous water-level changes due to elastic deformation of monitored groundwater reservoirs and to crack dilatancy in the water-saturated rocks.