Connection of scattering principles: focusing the wavefield without source or receiver

Inverse scattering, seismic interferometry, and focusing are subjects usually studied as independent problems in different research areas. We speculate that a physical connection exists between them because the equations that rule these scattering principles have a similar functional form. With a visual explanation of the relationship between these principles, we describe the importance of the interaction between the causal and acausal Green’s functions and provide physical insight to emphasize the connection between these principles. Finally, we show how to reconstruct the Green’s function that radiates from a location where there is no source or receiver, going beyond seismic interferometry.