Retrieving reflections by source-receiver wavefield interferometry

Source-receiver wavefield interferometry has been proposed recently as an extension of classical correlation-based interferometry. Under idealized assumptions, it allows the Green's function between a source and a receiver to be reconstructed from boundary data that are collected using two closed contours of sources and receivers, respectively. An intuitive geometric description of this method, based on ray theory, can be used to design a method for reconstructing virtual-gather events that typically are lost when conventional interferometry is employed. In classical interferometry, events in the Green's function between two receiver locations are reconstructed by automatically finding a ray that emanates from a stationary source, passes through the virtual source, reflects off the structure, and finally is recorded by the second receiver. The common path to both receivers is then canceled by a suitable crosscorrelation. If illumination of the structure is not ideal, such a ray may not exist and the reflection is not reconstructed. Source-receiver wave interferometry can be given a similar geometric description. The reflection off the structure can be constructed using not one but multiple rays produced simultaneously by two stationary sources. This new redatuming technique proves successful in geometries in which classical interferometry fails. Extensive numerical simulations support these theoretical conclusions.