On the Formation of Global Inter-Source Correlations and Applications to Constrain the Interiors of the Earth and Other Terrestrial Planets

The cross-correlation stack of earthquake late-coda between seismic receivers on a global scale—global inter-receiver correlogram—exhibits numerous features that provide information on the Earth's structure. The cross-correlation stack between seismic sources (global inter-source correlogram) can also be constructed, and, in theory, it should reproduce the correlation features seen in the inter-receiver correlogram. However, practical attempts at global inter-source correlograms have not produced the theoretical expectations. Namely, the obtained inter-source correlograms are void of discernible correlation features. Here, we address this problem and document the steps that have to be undertaken to produce the inter-source global correlogram with the equivalent abundance of correlation features. We show that forming inter-source correlation features requires constructive contributions determined by specific source mechanisms and source-receiver geometries. They are overwhelmed by destructive contributions if seismic records of all available sources and source-receiver geometries are used. Building upon that, we present an effective procedure for constructing global inter-source correlations through a rigorous selection of source mechanisms and source-receiver geometries. The resulting inter-source correlations exhibit numerous prominent correlation features as predicted. Notably, this method enables the construction of global inter-source correlations in a special case with a single seismic receiver. Furthermore, we explore and demonstrate the feasibility of utilizing single-receiver inter-source correlations to constrain the interiors of the Earth and other terrestrial bodies. Our study facilitates practical applications of global inter-source correlations, providing additional constraints on the Earth's structure and offering an effective routine to probe the interiors of other planets and moons using currently affordable resources.