Inversion of teleseismic S particle motion for azimuthal anisotropy in the upper mantle: a feasibility study

SUMMARY We have developed a technique for the inversion of teleseismic S-waveforms in terms of azimuthal anisotropy in the upper mantle. We test different models of the Earth upper mantle by transforming the observed horizontal components into a synthetic vertical component and comparing this with the observed vertical component. The optimum model is found by minimizing the difference between the synthetic vertical component and the observed one. Using this method, we explore the possibility of constraining the distribution of azimuthal anisotropy with depth. We present examples of seismic observations where the data are clearly in favour of an anisotropic model. These observations can be interpreted in terms of two anisotropic layers with different directions of fast velocity axes.

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