Deep Structure and Dynamics of the Issyk-Ata Fault (Northern Tien Shan)

The identification of hidden areas of active faults in the Earth’s crust that can generate earthquakes is the most urgent problem in assessing the seismic hazard of various regions. The main goal of this study was a detailed study of the geophysical characteristics in the zone of individual segments of active faults in the Northern Tien Shan with electromagnetic geophysical methods. The structural line of the Issyk-Ata fault is clearly, but fragmentary, revealed on the surface by geological methods, since the tectonic disturbance is hidden by loose deposits of the Cenozoic age. The results of inversion of detailed magnetotelluric soundings in the fault impact zone of the fault made it possible to determine the position of the upper edge, width, depth, strike and inclination of the fault zone. At the stage of complex construction of 2D geoelectric models of the Issyk-Ata fault zone, the results of field profile soundings by the method of surface electrical resistivity tomography were used. To study the dynamics of the constructed block model of the fault zone, we considered variations in the following electromagnetic parameters that reflect the response of the geomedium to a change in its stress–strain state: impedance and tipper components, apparent resistivity and impedance phase, time–frequency series, and anisotropic properties. Based on this, estimates of the correlation between variations in electromagnetic parameters and lunar-solar tides and the spatiotemporal distribution of seismicity were made. This work was supported by the Russian Science Foundation under grant No. 22–27-00567.