Aliasing in prestack wavefield continuation migration

Brad Artman, Jeff Shragge, and Biondo Biondi

brad@sep, jeff@sep, biondo@sep

ABSTRACT

With the widespread adoption of wavefield continuation methods for prestack migration, the concept of operator aliasing warrants revisiting. While zero-offset migration is unaffected by spatial aliasing due to the migration operator, this is not the case for prestack migration. This problem arises in any situation where sources and receivers are not collocated at every sampling point. Once anti-aliasing criteria have been calculated, aliased energy may be prevented from entering the image space by using a source function of appropriate band-width, or band-limiting the energy of the contributing data. As shot-profile migration is the most accurate and expensive imaging algorithm, data axes are commonly subsampled to save cost. We analyse the costs and benefits of implementing anti-aliasing measures to remediate unequal sampling intervals. While some bandwidth of the output image is lost in this process, it will attend to aliasing problems that will be most apparent in the shallow overburden and steeply dipping reflectors. Despite the loss in resolution, any proposed method still enjoys better bandwidth than source-receiver migration with the same data.