Three-dimensional magnetotelluric inversion using unstructured deformed hexahedral grids

Abstract Topography has a great influence on the inversion and interpretation of magnetotellurics. To improve the reliability of the inversion, the influence of topography must be eliminated, and inversion with topography is an effective solution. At present, three-dimensional electromagnetic inversion is still mostly based on finite difference forward modeling, but it is difficult to simulate complex topography using structured hexahedral grids effectively, and unnecessary densification of the grid extension area will be performed. The finite element method can use arbitrary grids to divide the area and is very suitable for simulating undulating topography. Therefore, this study uses unstructured deformed hexahedral grids to divide the calculation area, which can densify local key areas and reduce the number of grid divisions in the extended areas, ensuring calculation accuracy and relatively reducing the number of calculations. The effectiveness of the method is proved by inverting the theoretical model.