The plot above shows 2D slices from a 3D VSP volume (left) and a 3D surface seismic volume (right). The abutting image slices show the same discontinuous sand/shale section but the 3D VSP image has approximately two times the frequency content of the surface seismic image. Small faults and stratigraphic changes that control gas production in this area are much more visible in the 3D VSP image.