3D AEM forward modeling based on the poly-grid spectral-element method with average weighted conductivity

The accuracy and effectiveness of 3D EM forward modeling are two key points that affect inversion and data interpretation.AEM forward modeling based on the spectral-element(SE) method using regular/deformed hexahedral cells has been verified to be feasible.However, a conventional SE method with a certain physical property assigned to each discrete element still cannot avoid fine grids to discretize a complex model, leading to poor adaptability to complicated earth model.To address this issue, we take into account the nature of the high-order basis functions of the SE method and develop a modified SE method with average volume-weighted conductivity.Physical model discretization is separated from numerical grid discretization, so as to realize the detailed description of physical property change within each element and meanwhile avoid an increase in the number of the equation unknowns in forward modeling.We perform 3D frequency domain AEM forward modeling to examine the accuracy and efficiency of the modified SE method.Numerical tests demonstrate that the modified algorithm can achieve an accuracy not less than that of conventional modeling methods while using fewer degrees of freedom, thus improve the forward modeling efficiency.