3D inversion of CSEM data using finite element method in data space

In this study, we present an efficient and memory saving 3D inversion algorithm for interpreting controlled-source electromagnetic (CSEM) data using the total electric field formulation. To tackle CSEM problems involving complex geometries, we discretize the study domain for both forward and inversion problems using unstructured tetrahedral elements. Our inversion scheme combines the parallelized finite element (FE) method with the Gauss-Newton optimal strategy. Additionally, we transform the conventional model space inversion into data space inversion, significantly reducing the computation time and Random Access Memory (RAM) requirements during the inversion process. To begin, we validate the effectiveness and stability of the developed data space inversion algorithm by utilizing a synthetic land CSEM basin model and a synthetic marine CSEM model with bathymetry. These validation experiments further demonstrate that compared with the conventional model space inversion method, the computational efficiency of the data space inversion scheme is greatly improved and the memory required is significantly reduced. Furthermore, we apply the inversion method to survey CSEM data to demonstrate the practical applicability of the new inversion scheme.