Key points are not available for this paper at this time.
By inverting the azimuthal dependence of Rayleigh and Love dispersions (including the azimuthally averaged term) it is possible to separate the effect of anisotropy from other effects creating lateral heterogeneities (mainly thermal). The different steps of the tomographic method are described. In the first step, we retrieve the geographical distributions of the different azimuthal dispersion terms of Rayleigh and Love waves. For a complete slightly anisotropic medium, these distributions are dependent upon 13 combinations of elastic moduli. This number of parameters is too large and in order to interpret these distributions as simply as possible in terms of elastic properties of the medium, some realistic assumptions about the material can be made. The simplest way to explain the azimuthal distributions is to assume that the medium possesses a symmetry axis but contrarily to previous investigations, it is assumed that the orientation of this axis is not necessarily vertical. In that case, one shows how to retrieve simultaneously the 3-dimensional distributions of seismic velocities and of anisotropy characterized as a vector by an amplitude and the two angles of the symmetry axis. This complete process has been named ‘vectorial tomography’ and can provide valuable information about convection and also mineralogical composition.
Montagner et al. (Mon,) studied this question.