oa Constrained voxel inversion using the Cartesian cut cell method

Voxel inversion is a well-established method for constructing a physical property model from geophysical data. However, a limitation on Cartesian voxel inversion is that the voxel earth model is restricted to prism shaped elements which do not conform to geology and can lead to numerical artefacts. Octree and unstructured meshes have been used to overcome this limitation, but both add significantly to either the number of voxel elements, or to the complexity of the representation. We propose an alternative method which maintains much of the simplicity of the regular Cartesian voxel model while allowing very accurate geometric representation of geological surfaces: the Cartesian cut cell (CCC) method.

A significant geologic surface in most voxel inversions is the topography, which is very poorly represented by voxels. There are many other common geologic sub- surfaces including faults, contacts, unconformities, mineralized zones, etc. We demonstrate the necessity of improving the conventional voxel representation to ensure accurate geophysical modelling and how this is achieved with the CCC method. We also show the value of the CCC method in constrained inversion. These examples demonstrate that the CCC method allows accurate representation of geologic surfaces with a minimal extension to the simplicity of a conventional voxel model.