Vector-based image condition for 3D elastic reverse time migrations

Elastic reverse time migration (ERTM) requires separation of PP and PS reflections before, or as part of, applying the image conditions. Traditional P- and S-waves separation methods based on divergence and curl operators don't preserve the elastic vector information, and the non-normalized crosscorrelation image condition generates image amplitudes with no physical meaning. Thus a preferable workflow for isotropic ERTM should include a vector decomposition of the elastic wavefields and a vector-based image condition that directly uses the signed magnitudes of the decomposed vector wavefields to produce PP and PS images. The image condition involves the calculation of propagation directions of the decomposed P- and S-waves, which can be further utilized to efficiently generate PP and PS angle domain common image gathers (ADCIGs).