Here, I consider the simplest and probably most practical anisotropic model, that is a transversely isotropic (TI) medium with a vertical symmetry axis. Although, more complicated anisotropies can exist (i.e. orthorhombic anisotropy), the large amount of shales present in the subsurface makes the TI model the most influential on P-wave data Banik (1984).

In homogeneous transversely isotropic media with vertical symmetry axis (VTI media),
*P*- and *SV*-waves (I omit the qualifiers in ``quasi-*P*-wave" and
``quasi-*SV*-wave" for brevity) can be described by the vertical velocities
*v*_{v} and *v*_{sv} of *P*- and *S*-waves, respectively, and two
dimensionless parameters and Thomsen (1986).

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 non-hyperbolic moveout correction, if necessary),
dip-moveout removal, and prestack and post-stack time
migration. These two parameters are the normal-moveout velocity for a horizontal reflector

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8/21/1998