## PS-wave moveout in anisotropic media
of arbitrary symmetry and tilt

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

As previous studies of reflection moveout show, use of unconverted
P waves leads to formulae, which relate the moveout to only a limited
number of parameters specifying anisotropy. Use of converted PS waves
extends the number of parameters to, generally, complete set of twenty
one parameters. We present and test an approximate formula for
the reflection moveout of a wave converted at a horizontal reflector
underlying a homogeneous layer of arbitrary anisotropy symmetry.
For its derivation, we use the weak-anisotropy approximation. It leads
to an approximate formula for the square of the reflection traveltime
expressed in terms of A-parameters, parameters used to specify
anisotropy. The complete set of A-parameters represents an alternative
to twenty one independent elements of the stiffness tensor. Traveltimes
are calculated along reference rays of converted reflected waves traced
in a reference isotropic medium. Presented tests indicate that
the maximum relative traveltime errors are less than 1% for models
with P- and S-wave anisotropy of less or slightly higher than 10%
and less than 2% for models with P- and S-wave anisotropy of less
or slightly higher than 20%, respectively.

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*Seismic Waves in Complex 3-D Structures*, **31** (2022), 31-54
(ISSN 2336-3827, online at http://sw3d.cz).