A wavefront perspective on seismic data

What is it about?

Traditionally, seismic data consits of individual seismograms recorded at spatially separated locations on the Earth's surface. With the abundance of seismic sensors in crustal-scale seismic measurements with controlled sources and the installation of large-scale seismological arrays in earthquake seismology, the wavefield is sampled with unprecedented density and wavefronts can be tracked and measured across stations. With the aim of unifying active and passive-source seismology, we approach the redundancy of seismic data from a wavefront perspective and intruduce generalized approximations valid for reflection, diffraction and passive source excitation, expressed in two equally useful replacement media.

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Why is it important?

If signals are comparably weak, as is generally the case for back-scattering and, in particular, for diffraction off structural features with an extent below the dominant seismic wavelength, stacking and coherence arguments can be used for enhancement and for suppressing uncorrelated noise. The suggested wavefront picture contributes to unifying existing approximations and explains their observed differences in behavior under a rigurous and intuitive conceptual roof that is inspired by projections as they are described in geometrical optics. In addition, we suggest new approximations with unique properties that have not been used before.