The Magnetotelluric Dimensional Finite Element Forward Modeling, And

Magnetolluric(MT) is a kind of exploration methods of study of the structure of the earth using natural electromagnetic field, based on the difference between the rock for the foundation and precondition. Currently the inversion of MT data is still in one-and two-dimensional interpretation of inversion, but forward modeling is base of inversion, in this paper, the forward with topography is studied and become the basis of the forward.Two-dimensional magnetotelluric response with topography is calculated by finite element method in this paper, In the first, boundary value problems of the two-dimensional magnetotelluric is derived from Maxwell's, and its weak solution is getted by variational theory. Rectangular element is used for all models, and shape function for each element is linear interpolation and second interpolation. Last, the finite element solution is obtained by solving large, sparse linear system. By rectangular element, magnetotelluric response with topography is modeling by finite element methed. A forward program is made, and magnetotelluric response for different topography is study and distribution of magnetotelluric field is compared and analysised.The program is verified by comparison with the analytic response of a symmetrical ladders model and with finite difference results of laterally inhomogeneous model and topographic model.We discuss topographic effects in magnetotelluric surveys by two topographic models and confirm there lies in topographic effects in both transverse electric mode and transverse magnetic mode (especially the transverse magnetic mode).