## P-wave reflection-moveout approximation for horizontally
layered media of tilted weak-to-moderate orthorhombic symmetry

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

An approximate nonhyperbolic P-wave moveout formula applicable
to horizontally layered media of weak-tomoderate orthorhombic or
higher-symmetry anisotropy of arbitrary orientation is presented and
tested.
Weak-anisotropy approximation is used for the derivation of the formula,
in which the square of the reflection traveltime is expanded in terms
of weak-anisotropy (WA) parameters specifying the anisotropy of the
layers.
Due to the use of the weak-anisotropy approximation, the proposed
formula
is applicable to any offset. Its accuracy decreases with increasing
strength
of anisotropy. The relation between traveltimes and WA parameters in
the formula is transparent and relatively simple. For any offset along
an arbitrarily chosen single surface profile, the formula depends in
each
layer on its thickness, on the auxiliary reference P-wave velocity, on,
atmost, six WA parameters describing P-wave orthorhombic or
higher-symmetry
anisotropy, and on three Euler angles specifying the orientation of
symmetry
elements in the layer. Performed tests indicate that the maximum
relative
traveltime error does not exceed 2.5% for P-wave anisotropy about 25%.
Often,
the errors are considerably lower.

### Whole paper

The reprint can be obtained from
Ivan Psencik.

*J. appl. Geophys.*, **178** (2020), 104057.