3D nonlinear conjugate gradient inversion for frequency-domain airborne EM based on vector finite element method

Abstract

The 3D inversion is a challenging task in the research of the frequency-domain airborne electromagnetic (AEM) method due to the massive amounts of data and limited computational efficiency. In this paper, we introduce the 3D FAEM inversion based on the vector finite element method (FEM). Compare with the traditional nodal FEM, the vector FEM can improve the computational efficiency by reducing the number of variables and the scale of linear equations. To tackle the computational demands, in the calculation process we apply the PARDISO solver with shared-memory distributed-memory multi-processors to solve the multi-source forward linear equations and calculate the gradient of the objective function by adjoint equations. Then typical resistivity model with the anomalous body is carried out to verify the validity of the proposed method. Meanwhile, in allusion to the multi-solution problem caused by the inversion problem, we study the influence of typical initial models on inversion results. Finally, we applied our algorithm to invert field data. The inversion results demonstrate that the proposed method can obtain reliable AEM resistivity inverted results.