## Anisotropic common ray approximation
of the coupling ray theory

**Petr Bulant** &
**Ludek Klimes**
### Summary

The common ray approximation considerably simplifies
the numerical algorithm of the coupling ray theory for S waves,
but may introduce errors in travel times due to the perturbation
from the common reference ray.
At present, the common reference rays are routinely represented
by the isotropic common rays calculated in the isotropic reference
model, but they would better be represented by
the anisotropic common rays calculated in the anisotropic model.
The errors due to the anisotropic common ray approximation
of the coupling ray theory are usually considerably smaller
than the errors due to the routinely used isotropic common ray
approximation of the coupling ray theory.

We numerically calculate the travel-time errors
due to the anisotropic common ray approximation
in three 1-D models of differing degree of anisotropy,
and compare them with the errors
due to the isotropic common ray approximation.
The differences between the isotropic and anisotropic
common ray approximations of the coupling ray theory
are demonstrated on synthetic seismograms.
### Keywords

Coupling ray theory, common ray approximation, travel time,
seismic anisotropy, inhomogeneous media.

### Whole paper

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In: Seismic Waves in Complex 3-D Structures, Report 14,
pp. 107-122, Dep. Geophys., Charles Univ., Prague, 2004.

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