## Comparison of the anisotropic-common-ray
approximation of the coupling ray theory for S waves
with the Fourier pseudo-spectral method
in weakly anisotropic models

**Petr Bulant**,
**Ivan Psencik**,
**Veronique Farra** and
**Ekkehart Tessmer**
### Summary

The standard anisotropic ray theory does not work properly or even
fails when applied to S-wave propagation in inhomogeneous weakly
anisotropic media or in the vicinity of shear-wave singularities,
where the two shear waves propagate with similar phase velocities.
The coupling ray theory was proposed to avoid this problem. In it,
amplitudes of the two S waves are computed by solving two coupled,
frequency-dependent differential equations along a common S-wave
reference ray. In this paper, we test two recently developed
algorithms of the coupling ray theory. As a reference, we use the
Fourier pseudo-spectral method, which does not suffer from
limitations of the ray methods and yields very accurate results. We
study the behaviour of shear waves in weakly anisotropic media as well
as in the vicinity of intersection singularity or conical singularity. By
comparing the coupling ray theory results with the results of the Fourier
pseudo-spectral method, we illustrate clearly applicability of the
coupling ray theory in the mentioned situations.

### Whole paper

The paper is available in
PDF (2539 kB).

In: Seismic Waves in Complex 3-D Structures, Report 21,
pp. 167-183, Dep. Geophys., Charles Univ., Prague, 2011.