High-accuracy prestack depth migration and imaging using local harmonic basis beamlet

Beamlet migration using local cosine bases (LCB) has good image quality and high computational efficiency. However, local cosine beamlets have two symmetric lobes with respect to the vertical axis. This lack of uniquely defined direction-localization leads to inaccurate modeling of wave propagation in high contrast heterogeneous media, and is inconvenient for many operations in local angle domain. We proposed a new wavefield decomposition scheme using local harmonic bases (LHB), which is implemented by linear combinations of local cosine and local sine bases. Compared to Gabor-Daubechies frame (GDF) beamlet, LHB beamlet is much more efficient because LHB is still orthogonal and has fast algorithm, but it has directional localization which is similar with GDF. On the other hand, beamlet migration using LHB propagators has the same efficiency as LCB propagator but improves the accuracy due to the directional localization built in the propagators. The results of prestack depth migration using the synthetic data of the 2D SEG/EAGE salt model and 2D BP benchmark model demonstrate the good imaging quality and the ability of direction localization.