## Prevailing-frequency approximation
of the coupling ray theory
along the SH and SV reference rays
in a heterogeneous generally anisotropic medium
which is approximately uniaxial

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

The behaviour of the actual polarization of an electromagnetic wave
or elastic S-wave is described by
the coupling ray theory, which represents the
generalization of both the zero-order isotropic and anisotropic
ray theories and provides continuous transition between them.
The coupling ray theory is usually applied
to anisotropic common reference rays,
but it is more accurate if it is applied to reference rays
which are closer to the actual wave paths.
In a generally anisotropic or bianisotropic medium,
the actual wave paths may be approximated
by the anisotropic-ray-theory rays
if these rays behave reasonably.
In an approximately uniaxial
(approximately transversely isotropic) anisotropic medium,
we can define and trace the SH (ordinary)
and SV (extraordinary) reference rays,
and use them as reference rays
for the prevailing-frequency approximation of the coupling ray theory.
In both cases, i.e. for the anisotropic-ray-theory rays
or the SH and SV reference rays,
we have two sets of reference rays.
We thus obtain two arrivals along each
reference ray of the first set
and have to select the correct one.
Analogously,
we obtain two arrivals along each
reference ray of the second set
and have to select the correct one.
In this paper,
we suggest the way of selecting the correct arrivals.
We then demonstrate the accuracy of the resulting
prevailing-frequency approximation
of the coupling ray theory using elastic S waves
along the SH and SV reference rays
in four different approximately uniaxial
(approximately transversely isotropic) velocity models.

### Keywords

Wave propagation, elastic anisotropy, electromagnetic bianisotropy,
heterogeneous media, wave coupling,
approximately uniaxial (approximately transversely isotropic)
anisotropic medium,
anisotropic-ray-theory rays,
SH (ordinary) and SV (extraordinary) reference rays.

### Whole paper

The reprint is available in
PDF (4856 kB).

*Stud. geophys. geod.*, **61** (2017), 513-540.