Modeling of the magnetotelluric impedance in the Tien Shan region

The separation of information on deep layers and shallow geological noise i s an important point of the Russian-Chinese study of the crustal electrical conductivity in Tien Shan. This work analyzes the magnetotelluric impedanc e in terms of a quasi-3D thin-sheet model in order to improve results of th e previous 2-D interpretation of magnetotelluric soundings. The numerical m odeling was based on a composite map of the sedimentary cover thickness in the Tien Shan region, constructed from Russian and Chinese geological-geoph ysical data. The map was converted to a scheme of electrical conductance us ing the average resistivity of the sedimentary cover, which was derived Fro m the results of magnetotelluric studies conducted by Russian and Chinese g eophysicists in western and eastern Tien Shan, respectively. The model impe dance diagrams reveal 3-D effects of the Tarim, Dzungar, Chu, and Iii basin s.