Receiver-pair seismic interferometry applied to body-wave USArray data

Abstract

With seismic interferometry, reflections can be retrieved between stations positioned on the Earth's surface. In the classical form, the reflections are retrieved by a crosscorrelation of observations and an integration over subsurface sources. For a specific data set, 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 and call it receiver-pair seismic interferometry (RPSI). With this formulation, reflections can be retrieved even in the limiting case of only a single source. We illustrate the new relation both with synthetic data and data from the USArray, which is a large grid of stations covering the USA. The field observations are from an earthquake in Mexico. We show that RPSI can be applied both for a line and grid of receivers. When using isolated phases recorded over a line of stations inline with the earthquake, reflections are retrieved from the core-mantle boundary, which reflections can be ascribed to specific virtual source and receiver locations within the USArray. When using full responses as input to RPSI, the retrieved phases are an average over multiple virtual sources and receivers. Location is then only possible when the integrand is spatially windowed or when a clear leading term is identified. When using a grid of receivers, the location of the source does not need to be known, but spatially averaged instead of localized responses are obtained, also when isolated arrivals are used as input to RPSI.