Home – Home – Jornals – Russian Geology and Geophysics 2025 number 10

A significant problem with the magnetotelluric sounding (MTS) method is the influence of local near-surface inhomogeneities that distort MTS data across the entire frequency range. These distortions complicate the analysis and interpretation of data and, ultimately, the acquisition of information about the deep structures being studied. A widely used method for suppressing near-surface distortions is the normalization of MTS curves using spatial low-pass filtering. The aim of this study is to evaluate the effectiveness of this approach, including using weight functions proposed by the authors. A simple geoelectric model of the Earth’s crust containing a conductive sedimentary cover, a high-resistivity basement, and a three-dimensional conductive depression in the basement was compiled. Two model variants with a homogeneous upper part of the section and with multiple local near-surface inhomogeneities were considered. A synthetic magnetotelluric sounding (MTS) dataset was calculated for a system of profiles using three-dimensional modeling. The effect of near-surface distortions is observed from the data of the second version of the model, leading to a shift by level in the MTS amplitude curves. MTS curves were normalized using smoothing filters in a sliding window with different radiuses to suppress the distorting effect of near-surface inhomogeneities. Various weight functions of the filters were used, namely: for distance from the center of the sliding window, for the difference in amplitude from the average in the window and for the difference in the main directions determined by the polar diagrams of the module of the main component of the impedance tensor and the main component of the phase tensor. In general, the experimental results showed a high efficiency of normalization of the main components of the impedance tensor and the telluric tensor, and a lower efficiency of normalization of additional components.