Imaging Artifacts Using Pre-stack Gathers

Thanks to advances in computer technology wave-based methods like shot profile migration and reverse time migration (RTM) have become established methods during the last decade. However, RTM is also known for producing low frequency artefacts, when sharp velocity contrasts are present. These artefacts are created by the unwanted cross-correlation of head waves, diving waves, and backscattered waves, which are not included in the imaging condition. We apply the imaging condition with time-shift gathers to remove artefacts based on properties of wave propagation. The filters can be applied as a post-imaging process, and it therefore preserves all input data. Compared to regular noise filters the filtering with time-shift gathers yields superior zero time-shift images.