Premigration data anti-aliasing for reverse time migration

If the migration frequency is high (e.g., 50 Hz), reverse time migration (RTM) can be computationally very expensive and hardware demanding for large 3D data sets with large apertures. For this reason, while the vertical wave-propagation grid is chosen to be dense enough to hold the highest frequency content, a sparser than needed horizontal wave-propagation grid is often used to make high-frequency RTM affordable. As a result, the theoretically alias-free RTM operator suffers from aliasing issues when applied to high-frequency data with steep surface angles. To solve this aliasing issue, we propose first decomposing the input shot gathers of the common-shot RTM into the plane-wave domain using sparse inversion and then applying surface-angle-dependent anti-aliasing filters to individual plane-wave coefficients before transforming them back to the spatial domain. Using 2D synthetic and 3D field data examples, we demonstrate that our method allows RTM to migrate data with a frequency higher than the Nyquist frequency imposed by the horizontal wave-propagation grid without much suffering from aliasing problems.