Extension of the Finite-difference Contrast-source Inversion Method to 3D Geometries

We extend the finite-difference contrast-source inversion (FD-CSI) method to 3D geometries for solving seismic full-waveform inversion (FWI). The FD-CSI algorithm uses a finite-difference frequency-domain formulation. The most promising advantage of the FD-CSI method is that it does not require the explicit solution of the full forward problem in the inversion process, while some other popular inversion techniques require us to solve at least three forward problems in each iteration. Further, to enhance the quality of the profile reconstruction, the inversion is regularized employing a weighted L2-norm regularization term, which is effective for imaging structures with sharp boundaries, as illustrated in the numerical results. The weighting parameter of this extra regularization term in the cost function is determined automatically by employing the multiplicative regularization technique. This technique is robust in terms of noise suppression and in handling limited measurement data. We present some inversion results on the 3D SEG/EAGE salt model.