3D airborne electromagnetic forward modeling based on the multiscale hexahedral finite-element method

ABSTRACT Slow forward modeling is the main factor that restricts the practical use of 3D inversion and interpretation of airborne electromagnetic (AEM) data. To improve modeling efficiency with 3D AEM data, we develop a new multiscale finite element (MsFE) method based on unstructured hexahedral meshes. Compared to traditional 3D AEM forward modeling, the main advantage of our newly developed method is that it can simulate complex underground structures in the earth quickly. Because we can fit the earth’s topography or the anomalous bodies underground using a small number of hexahedral grids, we can quickly model them using MsFE. The main idea of the MsFE forward-modeling method is to construct an interpolation operator between a coarse and a dense mesh and use the interpolation operator to map the conventional finite-element coefficient matrix to the MsFE coefficient matrix and thus reduce the number of unknowns in the modeling process. This will vastly reduce the scale of the linear equations system. We validate our method by simulating a typical mountain peak model and determine its effectiveness by simulating numerous synthetic models and a model from Voisey Bay’s Ovoid sulfide deposit, Canada.