2D Elastic Frequency-domain Full–waveform Seismic Inversion Using the Varying PML Approach

In this work, we present a two-dimensional (2D) FWI method for elastic data inversion. The method is based on the multiplicative regularized Gauss-Newton inversion approach. The forward problem is a finite-difference frequency-domain (FDFD) method using a perfectly matched layer (PML) absorbing boundary condition. The PML is used to truncate both the forward and inversion domains. The PML is a medium with special material properties that are determined by the material properties of the physical domain. In the inversion process, the material properties of the physical domain are changing after each iteration; hence, the material properties of the PML medium will be modified accordingly. Otherwise, an artificial reflection caused by the PML medium will contaminate the simulated data corrupting the inversion result. This varying PML approach will affect the computations of the sensitivity matrix calculation (adjoint fields). The use of the varying PML approach has been introduced before for the acoustic problem. In this work we will discuss its extension for the elastic approximation and for multiparameter inversion (the Lam'e parameters and mass density).