Introduction

Velocity analysis based on a hyperbolic moveout model has been in wide use until now. Velocities estimated this way are routinely used to improve signal quality by stacking multifold seismic data. Also, the stacking velocity spectrum is used to obtain lithologic information about the subsurface. However, under the existence of anisotropy the hyperbolic moveout equation is no longer adequate to preserve signal resolution through stacking. Furthermore, stacking velocity estimates alone are not sufficient to distinguish among different lithologies.

In order to approximate anisotropic ray velocity, Muir (1985) introduced a practical anisotropic system as a rational form and lately another approximation as a form of truncated Fourier cosine transform was presented by Byun et al. (1989).

In this paper I examine the meaning of additional parameters, anellipticity q, in two anelliptic approximations for a transversely isotropy velocity curve, which result in non-hyperbolic moveout equations, and explore the usefulness of the two methods by applying them to the synthetic data.