Depth migration with a windowed screen propagator

A windowed screen propagator is applied to poststack and prestack depth mig rations. For complex structures with strong velocity contrasts, such as the saltdome-related structures where the velocity of salt body is much higher than that of the surrounding medium, the phase screen method or split-step Fourier migration fails to give an accurate solution for wide propagation angles due to the large velocity perturbations. To handle strong lateral ve locity variations, the PSPI and the extended split step Fourier migration m ethod with multiple reference velocities have been developed, but are costl y since they require a Fourier transform for each reference velocity. By co mbining the windowed Fourier transform and the interpolation technique toge ther, the windowed screen propagator improves both the accuracy for imaging steep reflectors and the computational efficiency. Comparisons with the ph ase-screen migration method demonstrate the potential applicability of the windowed method to subsalt structure imaging.