2D Simulation of magnetotelluric data using finite element method

Abstract

Finite element method to model plane-wave electromagnetic fields in 2D conductive structures has been developed. Triangular grids were used which readily conform to complicated geologic structures, unlike other existing numerical modeling techniques which are bound by the limitations of approximating complicated geologic structures using rectangular grids. Maxwell’s equations were treated as a system of 2nd order partial differential equations and transformed into a weak form using method of weighted residuals. Application of this method for 2D Simulation of Magnetotelluric (MT) data, in transverse electric (E-polarization) mode, revealed that to obtain accurate results, a minimum thickness of the air layer is added to the model and is a function of the lateral conductivity contrasts within the earth. In the numeral model example, a minimum of 50 km air-layer thickness was added to nullify lateral changes in conductivity. Furthermore, Magnetotelluric (MT) transfer functions: impedance, apparent resistivity and impedance phase were also computed and their graphs displayed against the horizontal profile (y in km).