Calculation of seafloor direct current electric potentials by 3D finite element method using isoparametric elements

Abstract

There has been a growing interest in the marine direct current (DC) methods for the marine exploration of a broad range of geological targets. In most geophysical applications of marine DC methods, it is necessary to model geoelectrical structures and seafloor topography whose shape, size, and electric conductivity vary in an arbitrary manner. In this study, we have developed a new 3D modeling code for marine DC potentials, which can be applied to various subbottom exploration targets. Our new code is based on an isoparametric finite element method and the Galerkin’s FE formulation approach can be effectively applied to arbitrary seafloor topography by using isoparametric elements. The new code can take into account the effect of seafloor topography as well as the response of 3D subbottom geoelectrical structures with current and potential electrodes at any arbitrary position. In order to examine the efficiency and ac developed computer program and FE formulation, we conducted numerical experiments using a layered deep water model, whose analytical solutions can be easily obtained for comparison. Thereafter, the developed code has been tested using synthetic examples such as a layered earth model of seafloor with simple topography. The results show that the code provides an accurate numerical model of seafloor DC potentials. Thus, the code can be effectively used for the interpretation of practical data.