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 kinds of
anisotropies can exist (i.e., orthrohombic anisotropy), the large
amount of shales
present in the subsurface implies
that the TI model has the most influence on *P*-wave data Banik (1984).

In homogeneous transversely isotropic media with a vertical symmetry axis (VTI media),
*P*- and *SV*-waves^{} can be described by the vertical velocities
*V*_{P0} and *V*_{S0} 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 correction, and prestack and post-stack time
migration. These two parameters are the normal-moveout velocity for a horizontal reflector

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7/5/1998