Wave‐equation migration with dithered plane waves

ABSTRACT Wave‐equation based shot‐record migration provides accurate images but is computationally expensive because every shot must be migrated separately. Shot‐encoding migration, such as random shot‐encoding or plane‐wave migration, aims to reduce the computational cost of the imaging process by combining the original data into synthesized common‐source gathers. Random shot‐encoding migration and plane‐wave migration have different and complementary features: the first recovers the full spatial bandwidth of the image but introduces strong artefacts, which are due to the interference between the different shot wavefields; the second provides an image with limited spatial detail but is free of crosstalk noise. We design a hybrid scheme that combines linear and random shot‐encoding in order to limit the drawbacks and merge the advantages of these two techniques. We advocate mixed shot‐encoding migration through dithering of plane waves. This approach reduces the crosstalk noise relative to random shot‐encoding migration and increases the spatial bandwidth relative to conventional plane‐wave migration when the take‐off angle is limited to reduce the duration of the plane‐wave gather. In turn, this decreases the migration cost. Migration with dithered plane waves operates as a hybrid encoding scheme in‐between the end members represented by plane‐wave migration and random shot‐encoding. Migration with dithered plane waves has several advantages: every synthesized common‐source gather images in a larger aperture, the crosstalk noise is limited and higher spatial resolution is achievable compared to shot‐record migration, random shot‐encoding and linear shot‐encoding, respectively. Computational cost is also reduced relative to both random and linear shot‐encoding migration since fewer synthesized common‐source gathers are necessary to obtain a high signal‐to‐noise ratio and high spatial resolution in the final image.