ESTIMATION OF NONLINEAR ELASTIC CHARACTERISTICS OF ROCKS FROM SEISMIC DATA

Abstract

Information on nonlinear elastic properties of in situ rocks can be derived from deterministic and random seismic signals: storm microseisms, quasi-monochromatic man-induced signals, seismic noise, and the coda of earthquakes. One approach is to monitor the velocities of deterministic signals. Velocity variations may be caused by strain processes occurring in the Earth, lunar and solar tides, air pressure variations, free oscillations of the Earth, etc. Another approach is to analyze the bispectral and trispectral characteristics of stationary (seismic noise) and quasi-stationary (earthquake codas) seismic processes. In this study information was obtained on the velocities of man-induced quasi-monochromatic seismic signals, and the bispectral characteristics of seismic noise in regions of varying geologic structure were calculated. The results are interpreted in terms of elasticoplastic model of the earth.