Results of inversion of distorted magnetotelluric sounding curves (numerical experiment)

The paper presents the results of a joint inversion of magnetotelluric sounding (MTS) curves taken at several stations without preliminary selection and normalization and distorted by the presence of lateral electrical-conductivity inhomogeneities in the medium. In the calculations, we used synthetic MTS data for a three-dimensional model. Preparation and interpretation of data are carried out by the Trefftz method using a numerical model of the field and MTS curve distortions. To solve the inverse problem and optimize the subsurface model, we used a nonlinear least-squares method and an iterative process with calculation of the sensitivity matrix and its singular decomposition. The target functional is determined by the discrepancies between the model and synthetic experimental apparent-resistivity curves corresponding to the elements of the impedance tensors on the lateral diagonal. The reliability of the reconstructed subsurface model is characterized by the dispersion of the deviations of its parameters from the parameters of the known model used for the preparation of synthetic experimental data. The joint consideration of distorted apparent-resistivity curves at several stations increases the reliability of interpretation results. The obtained solution to the inverse problem is approximate and can be used as a starting model for more complex algorithms and programs.