Approximate retrieval of the point source in anisotropic media: numerical modelling by indirect parametrization of the source

We propose an approximate approach to the waveform inversion of the mechani sm and source time function of a point earthquake source buried in an aniso tropic medium. We have modified the INPAR (INdirect PARametrization) invers ion algorithm used for isotropic media by taking into account that the arri val times of waves propagating in an anisotropic medium differ from those p ropagating in an isotropic medium. All other effects caused by anisotropy a re neglected. In the waveform inversion, we simply use the isotropic Green' s function for constructing synthetic seismograms, and match them with anis otropic waveforms. To estimate the accuracy of this approach, we performed a series of numerical experiments covering various station configurations, ranging from very dense to sparse, and exploiting either only P, or both P and S waves. Treating anisotropy in this simplified way is mainly projected onto additional spurious moment tensor components, whilst the double-coupl e orientation and the source time function remain largely unaffected. It ap pears that even fairly high anisotropy (24 per cent in P waves and 11 per c ent in S waves) can be treated by this approach without fatal loss of infor mation about the source.