Study on divergence correction method in three-dimensional magnetotelluric modeling with staggered-grid finite difference method

Divergence correction is significant both in accelerating three-dimension magnetotelluric modeling and in improving calculation precision. Based on three-dimensional magnetotelluric modeling with staggered-grid finite difference method, three different methods of divergence correction were presented by utilizing the characteristic that magnetic divergence in Maxwell equations was equal to zero. They include the direct divergence correction of magnetic field (DDCM), complex residual divergence correction of magnetic field (RPCM), and real residual divergence correction of magnetic field (RRCM). In order to compare the effect of the three different methods, we tested with three geo-electrical models: abutting quarter spaces, typical low resistivity and international standard model. The results indicate that, compared with the other two divergence correction methods and no divergence correction, RRCM has the advantages of shorter computation time, faster convergence and higher precision. In addition, it shows good stability and adaptability for different mesh generation schemes.