DISTURBANCE OF HIGH-FREQUENCY MICRODEFORMATIONS BY EARTHQUAKES AT TELESEISMIC DISTANCES

Abstract

The increased sensitivity and frequency resolution of the laser-interferometric strain seismometer makes it possible to undertake new types of investigation of the correlation between high-frequency microseism-induced deformations (HMD) and slow deformation processes in the earth's crust. In this paper, we present the first results of measurements, whose purpose was to elucidate the dynamics of temporal variations in the high-frequency microseism-induced deformations and to evaluate the response of the geophysical medium in the acoustic frequency range to excitation by seismic waves from distant earthquakes with various epicentral distances and intensities. The spectral and temporal behavior characteristics of the MDH's are similar to the effect of spontaneous coherent emissions (Dicke effect) familiar in nonlinear optics. Strong broad-band pumping of the medium in the vicinity of the instrument by seismic waves from an earthquake synchronizes, by means of the common field, the emissions by HMD oscillators, so the spontaneous emission process becomes collective in character. The conditions for excitation of collective emissions are satisfied in the case of strong earthquakes that exhibit some threshold intensity in the high-frequency interval.