Late Quaternary activity characteristics of the strike-slip Dongbielieke Fault in West Junggar, China

Abstract

The Dongbielieke Fault, an active fault that originated during the Holocene, is located at a key position in the West Junggar orogenic belt. The total length of NE-striking the fault is 120 km. Since the Late Quaternary, continuous activity on the Dongbielieke Fault has caused clear left-lateral dislocations at all morphological units along it, and a continuous linear steep ridge has formed on the eastern side of the Tacheng Basin. Using high-resolution UAV images and differential GPS to depict and measure the strike-slip dislocations at each river terrace level, it was found that the maximum left-lateral dislocations in the T5, T4, and T2 terraces are 30.7 m, 12.0 m, and 8.7 m, respectively. In addition, based on the geomorphic ages from optically stimulated luminescence analyses, we have limited the sliding rate of different terraces on the Dongbielieke Fault. The average left-lateral strike-slip rate since the late Quaternary of the Dongbielieke Fault is 0.91 ± 0.18 mm/a. Combining the GPS rates for North Tianshan with those for the Tacheng Basin, it is believed that the three large NE-trending strike-slip faults (Daerbute, Tuoli, and Dongbielieke faults) absorb a large amount of residual deformation in the area. This would allow the faults to maintain a higher left-lateral slip rate. In summary, analysis of surface faulting, Quaternary geology, seismicity, and measurements of Holocene morphology suggests that the Dongbielieke Fault is an active strike-slip fault with high seismic risk. However, it is unlikely that this fault could generate an earthquake of magnitude greater than 7.5. Our data do not allow for discussion of a more complex seismic cycle.