Wave propagation in isotropic and cross anisotropic layered media

To investigate the waveforms and the characteristics of the wave propagation in the isotropic and cross anisotropic layered media, the crosshole seismic method is simulated using a finite element model with a diagonal mass matrix and a direct integration of the equations of motion in the time domain. The effects of the type of excitation and the position of the receiver with respect to the source on the shape of the recorded motions are investigated. The times of arrival of the different waves are also calculated based on a curved ray path theory. The results of the ray path model are compared with the finite element solutions to assess the accuracy of this much simpler procedure as a means to interpret the experimental data and to determine the material properties. The results obtained by the two methods are in good agreement as far as the times of arrival of the waves are concerned although the ray path model cannot provide the complete waveforms.