We have extended the method of elastic wave-vector decomposition to general heterogeneous anisotropic media.
The simplest way to define the two S modes in such media is to sort them based on the magnitude of their phase velocities. However, this creates difficulties for wave-mode separation and wave-vector decomposition because of the polarization discontinuity at the singularities where the S modes are not easily separable. Using an analytical expression for locating the S-wave singularities in low-symmetry media, we propose to calculate the proximity to the singularity at a given phase direction and to define the area in which a filtering can be applied to reduce the planar artifacts caused by the local discontinuity of polarization vectors at the singularities. The amplitudes affected by the filtering process are additionally compensated by the technique of local signal-noise orthogonalization. Our computational experiments confirm that the proposed method presents an effective way to separate wavefields corresponding to each of the three wave modes in heterogenous anisotropic media. It is appropriate in applications to true-amplitude seismic imaging and inversion.
Elastic wave-vector decomposition in heterogeneous anisotropic media