## Determination of P-wave anisotropic parameters
and thickness of a single layer of arbitrary anisotropy
from traveltimes of a reflected P wave

**Han Xiao** **&**
**Ivan Psencik**
### Summary

We present an inversion scheme allowing estimates of the thickness
of a layer and its parameters from traveltimes of the wave reflected
from the bottom of the layer. We concentrate on unconverted P wave
reflected in a homogeneous layer of arbitrary anisotropy symmetry
and orientation. The inversion scheme is based on the approximate
travel-time formula derived under the assumption of weak anisotropy.
For the description of anisotropy, the so-called A-parameters, which
represent an alternative to standard elastic moduli specifying anisotropic
media, are used. Nine of fifteen P-wave A-parameters, which describe
P-wave propagation in weak-anisotropy approximation, can be determined.
The thickness of the layer may be either a sought or known quantity.
If an additional information about the orientation of symmetry elements
is available for higher-symmetry anisotropy, the corresponding
phase-velocity surface can be reconstructed. Synthetic tests indicate
that the inversion scheme works very well for weak anisotropy
(less than 10%), yields reasonable results even for anisotropy stronger
than 20%. The scheme has tendency to overestimate the thickness of
the layer if it is a sought parameter.

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*Seismic Waves in Complex 3-D Structures*, **30** (2020), 9-28
(ISSN 2336-3827, online at http://sw3d.cz).