A comparison between numerically calculated and formula based scattering coefficients for anisotropic media.

摘要

A numerically based program TAVRT (Tilted Anisotropic Viscoelastic Reflection and Transmission), which calculates scattering coefficients for generally anisotropic media with arbitrary tilt, is tested for isotropic, VTI and monoclinic anisotropic media. The results agree with those of the scattering coefficients calculated via analytical formulae found in the literature. TAVRT is also tested for the HTI case and the results are in good agreement with those calculated using the Seismic Unix program program refRealAziHTI (Ruger, 2001; Stockwell, 1997) which computes the exact scattering coefficients numerically for interfaces between two HTI media having the same symmetry plane.; Formulae for SH-wave scattering coefficients for an interface between two tilted VTI media with angles ϕ1 and ϕ2 about the x2-axis have been derived and their results matched very well those of TAVRT.; The program TAVRT can be used to have more confidence about new derived exact and approximate scattering coefficient and group velocity formulae. It can be also used to study more complex anisotropic media.; For tilted VTI media, it is found that the scattering coefficients vary with tilt, but are unaffected by the sign of the tilt angle of the lower medium, i.e., the scattering coefficient for an interface between two tilted VTI media with angles ϕ1 and ϕ2 and the scattering coefficient for an interface between two tilted VTI media with angles ϕ1 and -ϕ2 are equal.; For tilted VTI media at pre-critical angles of incidence, the magnitude of the reflection coefficient is inversely proportional to the absolute value of the tilt angle of the upper medium. The magnitude of the transmission coefficient is directly proportional to the absolute value of the tilt angle of the upper medium.; In general, the angle of incidence and the angle of reflection are different for tilted VTI media.