Institute of Computational Mathematics and Mathematical Geophysics

Abstracts

Mathematical problems in geotechnologies

The process of radiation of seismic wave fields with the help of powerful seismic vibrators is accompanied by a complex of physical phenomena as taking place in the vicinity of a source and having the continuation at significant distances from it. The present paper is dealt with the analysis of these phenomena and the estimation of their quantitative characteristics.

Alongside with a seismophysical field, the radiating "vibrator - ground" system generates acoustic and electromagnetic fields . In this connection, the authors have shown, that the acoustic signals can be recorded (under certain atmospheric conditions) at distances of tens kilometers from a source. Seismoelectromagnatic signals were recorded in a near zone. The mechanism of their excitation is connected with the action of a seismic wave on the magnetic sensor. Coincident with the processes of excitation by vibrators of the fields of various physical nature the nonlinear physical effects occur in the source zone resulting in appearance of the lower and the higher multiple frequencies in seismic oscillations. Such effects are caused by specific features of the construction of a definite type of a source, as well as by processes of interaction of a source with ground, and also by mechanical properties of the latter. For example, the nonlinear effects of radiation inherent to the vibrator CV-100, are caused first of all by the violation of the condition of continuity of the vibrator with the underlying surface.

In operation on the basis of data of the theoretical analysis and experiments the quantitative estimations of effects of nonlinearity, exhibited in above-stated types of fields, are obtained. The estimations are obtained on distances up to 300 kms for powerful vibrators: centrifugal -CV-100 and hydroresonance -GRV-50.

The influence of effect of nonlinearity to a increase of quality of selection of seismic waves is proved.

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