Imaging Beneath Igneous Sills Using Reverse Time Depth Migration

A variety of imaging problems are associated with igneous sill complexes. Existing processing solutions provide good images of the shallowest sills, but are unsuitable for the imaging of deeper sills, for the steep dips associated with the sill feeder mechanisms and for resolving the sedimentary sequences underlying the intrusions. In this paper we construct a 2D model incorporating a variety of sill geometries. We use the model data to demonstrate that existing one-way depth imaging technology cannot provide adequate images. Internal multiples are also an issue for consideration. Reverse Time Depth Migration is used for the first time to provide accurate images of the sill feeder structures and sedimentary sequences beneath the sills. This powerful imaging approach has the potential to dramatically improve image quality in the North Atlantic continental margins regions such as the NW of Ireland, Britain and Norway. Results will benefit those studying sill emplacement and those exploring beneath igneous intrusions.