In homogeneous transversely isotropic media with a vertical symmetry axis (VTI media), P- and SV-waves can be described by the vertical velocities VP0 and VS0 of P- and S-waves, respectively, and two dimensionless parameters and Thomsen (1986). Tsvankin and Thomsen (1994) and Alkhalifah (1997a) demonstrated that P-wave velocity and traveltime are practically independent of VS0, even for strong anisotropy. Thus, for practical purposes, P-wave kinematic signatures can be considered a function of just three parameters: VP0, , and .
Alkhalifah and Tsvankin (1995) further demonstrated that a new representation in terms of just two parameters is sufficient for performing all time-related processing, such as normal moveout correction (including nonhyperbolic moveout correction, if necessary), dip-moveout removal, and prestack and post-stack time migration, assuming that the velocity varies only vertically. These two parameters are the normal-moveout velocity for a horizontal reflector