3D CSEM frequency-domain modeling and inversion algorithms including topography

Abstract

Rough topography encountered when conducting controlled-source electromagnetic (CSEM) surveys significantly distorts electromagnetic (EM) fields. However, there have been few studies on the accurate consideration of topography into modeling and inversion algorithms. We have developed a three-dimensional (3D) CSEM inversion algorithm based on the forward modeling algorithm which rigorously incorporates topography based on an edge-based finite element (EFEM) method. We focused on the strict reflection of topographic information to the modeling algorithm and the accuracy of the algorithm was verified through comparing with the semi-analytic solutions. In numerical experiments, we successfully performed the inversion of data obtained from a ridge and valley model. This implies that real data acquired at rough terrain can be handled reasonably by using the inversion algorithm developed in this study.