The design of stable, sparse wavefield extrapolators using projections onto convex sets

We present the results of poststack explicit depth migration of the well-known 2D SEG/EAGE salt model zero-offset seismic data using sparse wavefield extrapolators. The extrapolators are designed to be sparse by forcing some of the very small complex-valued coefficients’ magnitude values to be zero. The proposed extrapolators design method combines the previously reported modified projections onto convex sets (MPOCS) for designing explicit depth frequency-space (⁠$f-x$⁠) wavefield extrapolation operators with hard-thresholding of the small extrapolators coefficients’ magnitude. The real and imaginary parts of the MPOCS operators, with small magnitudes, are replaced by zeros during the MPOCS algorithm iterations. The migrated result of the SEG/EAGE salt model data, using such sparse designed operators, shows comparable migrated results using the nonsparse version of the MPOCS extrapolation operators as well as the image obtained using the well-known phase-shift plus interpolation (PSPI) migration technique. Overall, the sparse operators result in poststack imaging computational savings (in terms of used flops) of about 28% when compared to poststack imaging of the same data using the nonsparse MPOCS designed operators, and of more than 87.77% saved flops using the PSPI technique.