## Applicability of the ray theory for S-wave propagation
in elastic weakly anisotropic inhomogeneous media

**Vaclav Vavrycuk**
### Summary

Propagation of P waves in elastic, weakly anisotropic, inhomogeneous
media can be studied by the ray theory without any problem.
Propagation of S waves in such media, however, creates more
complications in the ray theory. These complications are caused
mainly by the so-called S-wave coupling. It is known that the
standard zeroth-order ray theory is inapplicable, if the S-wave
coupling is significant in the wavefield. In this case, modifications
of the ray theory such as the coupling ray theory or the quasi-
isotropic approximation of the ray theory have so far been used to
reproduce the S waves correctly. We show, however, that the failure
of the ray theory is not principal, and that it can be overcome even
without modifying the ray theory. We show that the ray theory fails
because only the zeroth-order term of the ray series is considered.
If we include higher-order ray approximations in the solution, we
obtain correct results. On a simple example of a plane S wave
propagating in a weak transversely isotropic medium with a rotating
axis of symmetry we study the accuracy of the ray theory in
dependence on the number of higher-order ray approximations
considered in the ray solution.

### Whole paper

The paper is available in
PostScript (1256 kB !)
and GZIPped PostScript (213 kB).

In: Seismic Waves in Complex 3-D Structures, Report 8,
pp. 127-149, Dep. Geophys., Charles Univ., Prague, 1999.

SW3D
- main page of consortium ** Seismic Waves in Complex 3-D Structures **.