Azimuth-dependence of shear-wave splitting in EDA media: Two-dimensional three-component pseudo-spectral modeling

In order to evaluate the detecting performance of azimuthal dependence of shear wave splitting on preferred oriented cracks/fractures, we made analyses of seismic attributes variations with respect to crack/fracture density and orientation. A set of three-component gathers are obtained from two-dimensional modeling with the popular pseudo-spectral wavefield simulation method. In our modeling, the absorbing boundary and antiperiodic extension method are applied to suppress surface-observed synthetic seismograms from the layered models with different orientation azimuth and density of cracks/fractures. Then, the time-frequency analysis and splitting shear wave's polarization check techniques are adopted to understand azimuthal dependence of shear wave splitting on preferred oriented cracks/fractures. The results demonstrate that the orientation and density of cracks/fractures determine the delay time and polarization of shear-wave splitting. With density of cracks/fractures increasing,the delay time of fast and slow shear wave increases. The delay time varies slightly with crack orientation, and reaches maximum at 45 degrees. On the other hand, by applying time-frequency analysis, we obtain that instantaneous dominant frequency is obviously different for different cracks/fractures orientation and it changes sharply with the shear wave splitting. Thus, the azimuthal variation of instantaneous amplitude and frequency as well as the delay time and fast splitting shear wave polarization can be used as seismic signatures of azimuth and density of orientated cracks/fractures.