3D Gravity Inversion Constrained By Stereotomography

We present a 3D inversion scheme for gravity data that incorporates a priori information about the subsurface structure from seismic stereotomography. The velocity models recovered by stereotomography are smooth, but the coherent reflection events are well positioned. Assuming that a seismic impedance contrast also represents a contrast in the bulk density, these coherent events can be used to build a structural model of the subsurface. Our 3D gravity inversion scheme allows for sharp parameter contrasts at known structural boundaries. Reducing the weight of the smoothness regularization at structural boundaries leads to density contrast models that reflect the a priori information on the subsurface. The proposed scheme was tested on a synthetic model reflecting a salt scenario. A body with a constant low density and a constant high velocity is located in the center of our test model. The background is layered and the velocities and densities increase with depth. The density contrast of the anomalous body is therefore positive at the top and negative at the bottom with a nil-zone in between. We are able to recover this density gradient by using the structural information given by stereotomography.