LIBRARIES EXPERIMENTAL STUDY OF SEISMIC SCATTERING BY A PENNY-SHAPED CRACK

Ultrasonic model seismology was applied to a study of scattering of P-waves by a dry and a fluid-filled crack. Three experiments were con-ducted. The first provided background information on the model medium and served to develop experimental techniques. The data from the other two experiments were used to test the applicability of a number of seismic techniques to the determination of the crack's size, orienta-tion, and location by studying the scattered signal. The technique of wavefront reconstruction was used to analyse a data set consisting of first arrival times and amplitudes of the com-bined incident and scattered wavefields. The amplitude distribution of the reconstructed wavefronts at various depths in the model showed that the signal scattered by the dry crack resembles that radiated by the sudden opening of a tensile crack, though the sense of the motion is reversed