## Moveout approximation for a P-SV wave
in a moderately anisotropic homogeneous DTI layer

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

We derive and test the moveout formula for converted
P-SV (or SV-P) waves in a homogeneous, weakly or
moderately anisotropic, transversely isotropic layer
with axis of symmetry perpendicular to a dipping reflector
underlying it. Instead of commonly used Taylor series
expansion of the squared traveltime with respect to the
offset, we use weak-anisotropy approximation of the
exact traveltime formula. We replace the exact traveltime
along the actual ray of a converted wave by its first-order
weak-anisotropy approximation along a ray in a nearby
reference isotropic medium. The traveltime formula is
derived in the plane defined by the source-receiver line
and the normal to the reflector. The source and the
receiver may be situated arbitrarily in the model, the flat
reflector may have an arbitrary 3D orientation.
The accuracy of the proposed moveout formula is tested on
models with varying strength of anisotropy for a varying
dip of the reflector. In isotropic media, the formula
yields highly accurate results with relative traveltime
errors not exceeding 0.5%. In anisotropic media of P- and
SV-wave anisotropy of about 25% and 12%, respectively,
relative traveltime errors do not exceed 2%.

### Whole paper

The reprint can be obtained from
Ivan Psencik.

*Journal of Applied Geophysics*, **159** (2018), 690-696.