## Properties of weak contrast PP reflection/transmission
coefficients for weakly anisotropic elastic media

**Ivan Psencik** **&**
**Jorge Leonardo Martins**
### Summary

Approximate formulae for *PP* reflection/transmission (R/T) displacement
coefficients for weak contrast interfaces separating weakly anisotropic
media of an arbitrary symmetry are presented. The coefficients have a
form of a sum of a well-known approximate *PP* reflection/transmission
coefficient for weak contrast interfaces separating two background
isotropic halfspaces and a correction due to weak anisotropy. The
correction is controlled, linearly, by the so-called weak anisotropy (WA)
parameters. The coefficients are defined with respect to an arbitrary
isotropic background. The coefficients can describe reflection and
transmission not only in low symmetry weakly anisotropic media but
also in media with higher symmetry (orthorhombic, hexagonal) but with
arbitrarily oriented axes of symmetry. For anisotropies of higher
symmetry, for which approximate formulae for R coefficients of other
authors exist, we discuss the differences between these and our formulae
and their effects on accuracy of approximate coefficients. Performance
of the approximate formulae for reflection coefficients is tested on
models with weak anisotropy and weak contrast interfaces as well as
on models whose anisotropy and velocity contrast are in no way weak.
Even in the latter case, the formulae yield satisfactory results.
Accuracy of the approximate *R*_{PP} coefficient in dependence on the
choice of the background is then investigated. Presented formulae are
convenient for solving an inverse problem: determination of contrasts
of parameters of anisotropic media surrounding an interface. Sensitivity
of the approximate *R*_{PP} coefficient to basic weak anisotropy (WA)
parameters is presented.

### Whole paper

The paper is available in
PostScript (1444 kB !)
and GZIPped PostScript (315 kB).

In: Seismic Waves in Complex 3-D Structures, Report 8,
pp. 151-170, Dep. Geophys., Charles Univ., Prague, 1999.

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