ИСТИНА

The direct problem of electrical sounding of a medium with a ground surface is solved by the Integral Equations Method. The numerical method is based on the triangulation of the computational domain, adapted to the shape of the relief and the measurements line. The numerical algorithm is tested by comparing results with the known solution for horizontally layered media and by checking the fulfillment of the "reciprocity principle”. The results of simulations have also been tested in artificial physical models. Then simulations are carried out for a twolayered media with a relief of the surface. Synthetic measured data have been obtained for a 2D relief form with the underlying layer at given depth h and resistivity ρ2. The quantitative effects of the influence of the relief form and media parameters (depth h, resistivities ρ1 and ρ2) to the apparent resistivity curves are established. Then synthetic data are entered into 2D inversion programs. Calculations show that the apparent resistivity anomalies lead to significant distortions of the interpretation results. Modelling on the base of Integral Equations Method allows one to estimate the level of false anomalies that appear due to topography.