Approximations to seismic velocities in anisotropic media

Faranak Mahmoudian, R. James Brown

Vertical and horizontal transverse isotropy (VTI and HTI) provide good models for wave propagation in many rock media. Expressing the exact body-wave velocities in TI media requires five parameters (in addition to density); expressing just the exact P-wave velocity requires four. That is more than can usually be estimated from surface seismic data. In this report we review a recent paper by Fowler, who makes several practical approximations for P- and S-wave phase and group velocities, each using only three parameters. It is shown, among other things that, with a good choice of parameterization, P-wave velocities become nearly independent of vsz, the vertical S-wave velocity. We propose some further potentially valuable extensions on Fowler's work