Coda-correlation Wavefield: State of the Art and Recent Advances

Abstract:

Coda-correlation, the cross-correlation of seismic recordings many hours after an earthquake origin, rises as a new paradigm in global seismology, both as a phenomenon and a new method. As a phenomenon, it has been documented both in terms of observations and theory, but some details are still being defined. As a method, it allows new constraints on Earth’s internal structure. Here, we demonstrate the fundamentals of processing, utilizing and interpreting correlation features in global correlograms.

We first show how to obtain coda-correlation features based on the formation theory of coda-correlation and we demonstrate how to dissect these features in terms of their constituents. Our approach circumvents distortions of relevant correlation-features due to a mixture of various constituents and inaccuracies introduced in data processing. We then derive the relationship between the obtained features and Earth’s structure. The relationship allows inference of Earth’s structure based on the timing of coda-correlation features and their constituents. Finally, we demonstrate the feasibility of the new method via several practical examples. We argue that coda-correlation will be indispensable in advancing fine-resolution illumination of Earth’s interior in the coming decades.