## PS reflection moveout in a homogeneous
anisotropic layer of arbitrary symmetry and tilt

**Veronique Farra** **&**
**Ivan Psencik**
### Summary

Use of unconverted reflected PP waves leads to moveout formulae, which
relate the moveout to
only a limited number of parameters specifying anisotropy. Use of
converted reflected PS waves
extends the number of parameters to, generally, a complete set of
twenty-one parameters. It
leads, on the other hand, to more complicated formulae and phenomena
unknown from studies of
unconverted PP waves. In anisotropic media one has to deal with the
existence of two S waves
and their singularities, acoustic approximation cannot be used. We
present and test approximate
formulae for the reflection moveout of PS waves converted at a
horizontal reflector underlying
a homogeneous layer of arbitrary anisotropy symmetry and orientation.
For their derivation, we
use the combination of weak-anisotropy approximation and A-parameters
specifying anisotropy.
The complete set of twentyone A-parameters represents an alternative to
twenty-one independent
elements of the stiffness tensor. In addition to the moveout formulae
for separate PS1 and PS2
waves, we also present moveout formula for a P to common S wave whose
traveltimes represent an
average of traveltimes of PS1 and PS2 waves. Use of the P to common S
wave reflection leads to
several simplifications. Presented tests indicate that for most offsets
and models with P-wave
anisotropy up-to to 26% and S-wave anisotropy over 25%, the relative
traveltime errors do not
exceed 2.5%.

### Keywords

Reflection moveout, arbitrary anisotropy, PS wave reflections, common S wave.

### Whole paper

The reprint can be obtained from
Ivan Psencik.

*J. appl. Geophys.*, **215** (2023), 105062, 13 pp.