One of the methods used to monitor the developing geodynamic processes in seismic-prone zones is based on the regular sounding of a medium by powerful seismic vibrators, with a subsequent analysis of the time dynamics of the seismic field parameters.
Such a monitoring is accompanied by certain nonlinear processes taking place at the stages of radiation and propagation of seismic oscillations. One of them is due to peculiarities of constructions of different vibrators and the processes of their interaction with the underlying surface. Other processes develop in a medium of seismic wave propagation. Such processes enrich a seismic wave field with additional lower and higher frequency components. In this paper, it is shown that the allowance for these processes increases the noise immunity of vibrational correlograms (analogs of explosive seismograms), as well as their time resolution, contributing to an increase in the accuracy of measurements of the arrival times types of the main wave types.
A modern concept of the earthquake source development is similar to that of development of a system of cracks. Broadening the spectra of the initial sounding seismic oscillations also results from the vibroseismic sounding of fractured dilatancy media typical of earthquake-prone zones. The applicability of parameters of the wave field nonlinearity in the form of possible prognostic characteristics of the earthquake source development is justified. The results of analysis and conclusions presented in this paper are based on numerical calculations and experiments.
The experiments were carried out when monitoring a 355-km long Earth's crust zone in the periods of the lunar-solar tides. It is shown that allowance for the ratios between high and first harmonics of seismic wave fields provides invariance of the positive results of monitoring with respect to inevitable seasonal and instrumental fluctuations of the intensity characteristics of the radiation field. At the same time, a high sensitivity of the relations to small variations of stresses in the Earth's crust is retained.