Fresnel-Volume-Migration of Single-Component Seismic Data

Abstract

In standard KPSDM implementations of Kirchhoff prestack depth migration (KPSDM) the wavefield is smeared along two-way-traveltime isochrones. In the case of sparse sampling or limited aperture the image is sometimes affected by significant migration noise. Some modifications have been proposed which aim at reducing these artefacts by constructing a specular path of wave propagation derived from the slowness of coherent phases in the seismogram section and the heuristic restriction of the imaging operator to that wave path. Here we propose another physically frequency-dependent approach by using the concept of Fresnel-Volumes. Firstly the emergence angle at the receiver is determined by a local slowness analysis. Using the emergence angle as the starting direction a ray is propagated into the subsurface and the back-propagation of the wavefield is restricted to the vicinity of this ray according to its approximated Fresnel-Volume. We describe the procedure and show applications to a synthetic model as well as a real data set over a salt pillow in North Germany. Compared with standard KPSDM the image quality of our Fresnel-Volume-Migration is significantly enhanced due to the restriction of the migration operators to the region near the actual reflection point.