The characteristics of active deformation and strain distribution in the eastern Tian Shan

Abstract

The Tian Shan is one of the largest and most active intracontinental mountain belts, and its active deformation has attracted much scientific attention. In this study, we investigated the characteristics of active deformation in the most complex, eastern Tian Shan through the analysis of focal mechanism solutions since 1976, velocity vectors of 25 years geodetic measurements, and existing studies on active tectonics. The results demonstrate that: (a) ~3.5 mm/year of convergence is accommodated by the southern Junggar fold‐and‐thrust belt, forming a series of active thrusts and folds. The Bolokelu‐Aqikekuduke Fault is a transpressional structure, accommodating ~1 mm/year shortening and ~1.5 mm/year of right‐lateral shear strain; (b) Most of the convergence in the Huola Shan region is absorbed by the North Luntai Fault, and the right‐lateral shear strain is probably accommodated by the Kaidu River Fault and the Songshudaban Fault; (c) Active deformation in the eastern Tian Shan under oblique convergence is mainly partitioned into widespread compressional deformation (folding and thrusting) and dextral displacements on the NW‐trending faults. Nevertheless, left‐lateral strike‐slip motions have also been observed, suggesting that further constraints on the kinematics and deformation rates of structures especially the intermontane structures are still needed with the aim of achieving a better understanding of strain distribution in the study area.