3-D Time migration velocity model building using CRS-based pre-stack diffraction separation

What is it about?

3-D imaging of diffractions is still a challenge since they are inherently of 3-D nature. We need to consider three dimensions if we want to correctly image diffractions. Seismic diffractions carry a lot of information about the subsur-face especially in regions with small-scale heterogeneities. If diffraction-only data are available, they permit to extract information in addition to that obtained from reflection processing. In this work, firstly, we present a new 3-D workflow for pre-stack diffraction separation and enhancement based on common-reflection-surface (CRS) attributes. At the second step, we perform PreSTM velocity analysis using diffraction-only data by evaluating the semblance norm. Application to a 3-D synthetic data reveals that pre-stack diffraction separation shows advantages over post-stack diffraction separation. Moreover, the diffraction-only gathers allow to determine time migration velocities in pre-stack domain which favourably focus diffractions.

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