Body-wave receiver-pair seismic interferometry

With seismic interferometry reflections can be retrieved between station positions. In the classical form, the reflections are retrieved by a crosscorrelation of observations and an integration over subsurface sources. For a specific dataset, however, the actual source distribution might not be sufficient to approximate the source integral. Yet, there might be a dense distribution of receivers allowing an integration over the receiver domain. We rewrite the source integral to an integration over receiver pairs. With this formulation, reflections can be retrieved even in the limiting case of only a single source. However, with respect to the classical formulation, an additional stationary-phase analysis is required. We show that - with a 1D approximation - only one subsurface source allows estimating a velocity model and a reflectivity profile of the subsurface.