Angle gathers for shot-record migration by local harmonic decomposition in 73rd Ann

It is now recognized that shot-record wave-equation migration is the best method for imaging in complex media. However, it is also recognized that producing one output image is not enough. Velocity analysis can only be done when a gather is produced, as well as AVO analysis or multiple attenuation. This paper starts by describing the local harmonic decomposition: it is an efficient algorithm which can be used to extract angle information from a wavefield. It is then shown that this algorithm can be used to produce reflection angle gathers. A synthetic test proves that these gathers are centered on zero opening angle whatever the dip and the absence of artefacts. Results from the application of this algorithm on real 3D OBC data are shown.