Imaging of VTI media from wide-aperture data by frequency-domain full-waveform inversion

Seismic imaging of anisotropic media is one of the most challenging problem in exploration geophysics because of the possible coupling between the different anisotropic parameters. In this study, we develop a frequency-domain full-waveform inversion (FWI) method for imaging 2D visco-elastic VTI media from wide-aperture data. The forward problem relies on a finite-element discontinuous Galerkin method on unstructured triangular meshes that allows for accurate seismic modeling in complex media with reflectors of arbitrary shape. The inversion relies on a quasi-Newton algorithm which allows for proper scaling of misfit-function gradients associated with different parameter classes. The model parameters are either the P and S wave speeds on the symmetry axis and the Thomsen’s parameters ! and ", or the stiffness coefficients c11, c33, c13 and c44. We first present a review of the diffraction patterns of each anisotropic parameter classes to assess the best parameterization of the inverse problem. Second, we present some preliminaries examples of FWI with simple synthetic model. Results highlight the coupling between the parameters and the difficulty of imaging the ! parameter from surface data.