Perpustakaan Digital ITB

Acoustic transversely isotropic medium with a vertical symmetry axis (acoustic VTI) is a very practical anisotropic model for P-wave kinematic analysis. However, apart from P-wave, there is also one additional wave that propagates in this medium, widely known as S-wave artifact. This S-wave possesses bizarre properties and is thoroughly different from the conventional shear waves in elastic VTI media. This paper is devoted to the analysis of S-wave artifact moveout approximations and the Dix-type inversion in acoustic VTI media. We consider four different traveltime approximations originally developed for P-wave and apply them for S-wave moveout. The accuracies of P- and S-waves approximations are numerically compared for both homogeneous and multi-layered acoustic VTI models. With an additional reference ray, the generalized moveout approximation performs the best for S-wave traveltime for a large range of offsets. From the effective parameters estimated for P- and S-waves moveout approximations, we also estimate the interval layer parameters from corresponding Dix-type equations developed for P- and S-waves, respectively. The accuracy and feasibility of the Dix-type inversions are demonstrated in a multi-layered model test.