## Errors due to the anisotropic-common-ray approximation of the coupling ray theory.

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

The coupling ray theory
provides a continuous transition between the isotropic and
anisotropic ray theories, and is particularly
important at degrees of anisotropy and frequencies typical in
seismic exploration and structural seismology on all scales.
In the common ray approximation of the coupling ray theory,
only one reference ray is traced
for both anisotropic-ray-theory S waves,
and both S-wave anisotropic-ray-theory travel times are
approximated by the first-order perturbation expansion
from the common reference ray.
The common ray approximation thus considerably simplifies
the coding of the coupling ray theory and numerical calculations,
but may introduce errors in travel times due to the first-order
perturbation.
Fortunately, the accuracy of the common ray approximations
can be estimated by quadratures along the reference rays.
The accuracy of the common ray approximation depends
considerably on the selection of the reference rays,
and it is much worse for the isotropic common rays
calculated in the isotropic reference model,
than for the anisotropic common rays,
traced in the anisotropic model
using the averaged Hamiltonian of both anisotropic-ray-theory S waves.

### Whole extended abstract

The extended abstract is available in
PostScript (4 494 ! kB)
and GZIPped PostScript (1 017 ! kB).

Extended Abstracts of 68th EAGE Conference (Vienna),
EAGE, Houten, 2006, P183.

SW3D
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