Resolution analysis for full wavefield inversion and its application to time‐lapse

Full-wavefield inversion (FWI) estimates a subsurface elastic model by iteratively minimizing the misfit between observed and simulated data. Resolution analysis provides a framework for understanding what parts of model are better constrained by the data. However, the conventional SVD (singular value decomposition) approach to computing the resolution matrix is prohibitively expensive for FWI. We tested an iterative method (Lanczos algorithm) for computing an approximation to the resolution matrix based on a simple 3-layer model. We compared the results with the full SVD solution by ScaLAPACK. We find that after 150 iterations, the approximate resolution matrix agrees well with the full SVD solution. Then we applied Lanczos approach to 2D Time-Lapse analysis based on the SEAM model. The analysis shows that the approximate resolution matrix matches the inversion result.