Wavefronts in dissipative anisotropic media: Comparison of the plane-wave theory with numerical modeling

In a previous work, Carcione investigated the characteristics of wavefronts in a dissipative anisotropic (orthorhombic) medium by means of time-harmonic, homogeneous, plane-wave analysis. Here, we extend the theoretical analysis to a monoclinic medium and perform numerical experiments to investigate the transient response. Given a line source the forward modeling algorithm computes pure shear waves in the symmetry plane of the medium. The results of the theoretical analysis agree with those of our transient wave simulation. For instance, the onset of the wavefield coincides with the theoretical wavefront calculated with the unrelaxed (high-frequency limit) energy velocity. Moreover, while the wavefronts computed with the theoretical envelope and energy velocities coincide practically with a numerical evaluation of the energy location, using the group velocity yields a wrong prediction. Finally, as an interesting example, we present a medium where the wave behaves isotropically (cylindrical wavefronts) at a given frequency, but is strongly anisotropic at the low- and high-frequency limits.