PHYSICAL CAUSES OF DIURNAL VARIATIONS IN THE GEOACOUSTIC EMISSION LEVEL

Abstract

The results of geoacoustic (seismoacoustic) observations in seismoactive regions, which reflect variations in the characteristics of acoustic emission of rocks in natural conditions related to tectonic processes, can make a significant contribution to the development of the models of earthquake preparation. The results obtained during measurements in deep boreholes using high sensitivity geophones are very interesting, because one can observe in this case the fine effects of the response of geoacoustic emission (GAE) to the variations in the stress–strain state of the rocks. This is usually impossible during measurements at the daytime surface due to the high noise level. In this paper, we discuss the results of the analysis of synchronous measurements of the GAE and natural electromagnetic field (EMF) at frequencies close to 160 Hz. The measurements were carried out in a deep borehole near Petropavlovsk-Kamchatskii to elucidate possible physical causes of diurnal variations in GAE and their relation to the variations in the stress–strain state of the rocks.