Modeling of magnetotelluric fields within a block geoelectric model of the southern border of the Chu Basin (Northern Tien Shan)

Three-dimensional inversion of magnetotelluric fields made by 3D block modeling of magnetotelluric (MT) fields of geoelectric models permitted construction of alternative geoelectric models fitting real MT data. Based on their analysis, highly conductive zones have been identified at different depths of the crust. Their correct interpretation requires the use of reliable gravity, temperature, and seismic data. Sensitivity analysis of 3D MT model curves with respect to conductive crustal blocks has shown that it is advisable to use the maximum curves of the phase tensor to estimate the electrical conductivity of the crustal and mantle parts of the section. The information value of these curves is close to that of the maximum induction curve on mapping conductive blocks in the upper and middle crust. It is also shown that the real Wiese–Parkinson vectors provide high resolution on estimating the excess integrated conductivity of the crustal blocks. Therefore, magnetovariational sounding in the Northern Tien Shan should be continued.