On the symmetry of diffracted wavefronts

What is it about?

Due to comparably weak amplitudes, diffractions are hard to detect and often "hide" behind more priminent wavefield components such as reflections or transmitted waves - likely the main reason, why they are still rarely used in seismology. Nevertheless, they provide superior crustal illumination and are a reliable indicator of structural complexity. With a focus on controlled-source surveys, we discuss and utilize kinematic symmetries of diffractions that arise from the fact, that the back-scattering off a diffracting structure strongly resembles the uniform radiation of a passive source buried in depth. We conclude that diffraction is fully captured and described in data subsets of multi-coverage acquisitions and, consequently, can be enhanced by exploiting this characteristic redundancy of information.

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Why is it important?

In contrast to the commonly favored reflections, diffraction is not limited by Snell's law and, therefore, radiates uniformly, just like a passive source. As seismic diffractions are generally hard to detect, especially when uncorrelated noise is present, the discussed redundancy of information in the diffracted response is a discriminating criterion that helps to detect, separate and enhance diffractions in the prestack domain making them more accessible and usable in imaging and inversion.