A comparison of accuracy and computation time of three-dimensional magnetotelluric modelling algorithms

This paper presents a comparison of four different three-dimensional (3D) magnetotelluric (MT) modelling algorithms in terms of accuracy and computation time. Three of them use the finite difference method while the last one uses the edge finite-element method. The modelling algorithms are analysed with respect to governing equations, boundary conditions, solvers, preconditioners and static divergence correction. The accuracy of the algorithms is examined by simulating MT responses for two different models, both of which have anomalous bodies in simple background media. Although the simulated responses generally show good agreement, small discrepancies are observed over the anomalous bodies. These discrepancies are caused by the difference between the electric- and magnetic-field formulations used by the algorithms. The three algorithms using the finite difference method are adequate for 3D inversion of MT data since they produce solutions in a short computation time. Although the algorithm using the edge finite-element method requires longer computation time than the others, it can provide more accurate solutions and model surface topography.