3-D controlled source electromagnetic modelling based on unstructured mesh using finite element method

The forward modeling and inversion study on Controlled-Source Audio-Frequency Magnetotelluric method is very important to field work and interpretation of field data. One dimension forward modeling and inversion study has gotten lots of interest over the years and the technology has now been well developed. However, a wrong result may be obtained when the model varies laterally by using 1D numerical modeling, given that both the source used by CSAMT and the actual model are of 3D character. Hence, there is an urgent need to develop three-dimension (3D) forward modeling and inversion technique. To simulate complex geological model, this paper does study on three-dimension finite element modelling based on unstructured grid. We solved the primary field induced by the background model (1D) and the secondary field induced by the anomalous body, respectively, so as to avoid the singularity of the source and reduce the computation area. The algorithm was validated to modeling layered model by comparing its result with the result obtained from integral equation (IE) method. Then, numerical modeling was performed for a single conductive model and the electromagnetic response was analyzed.