East Tacheng (Qoqek) Fault Zone: Late Quaternary Tectonics and Slip Rate of a Left-Lateral Strike-Slip Fault Zone North of the Tian Shan

Although the Tacheng Basin may play an important role in accommodating crustal shortening north of the Tian Shan and west of the Junggar Basin based on observations of several conspicuous surface ruptures in satellite imagery, little is known about its late Quaternary tectonic activity. We analyze the tectonic geomorphology of the East Tacheng fault zone, including the subparallel NE-SW trending East Tacheng and Wuerkashier faults, using field observations, interpretations of satellite imagery, and construction of decimeter-scale digital elevation models from unmanned aerial vehicle surveys. Geomorphological features such as displaced stream channels and terrace risers, negligible vertical offset, opposite facing directions of a single fault scarp, and linear fault traces suggest that the East Tacheng fault is a nearly pure left-lateral subvertical strike-slip fault. The late Quaternary horizontal slip rate is estimated to be 0.4-2.0 mm/year, likely similar to 0.7 mm/year. Paleoearthquake studies in trenches reveal that the most recent earthquake occurred between 3.1 and 0.5 ka. The Wuerkashier fault, which shows pristine surface ruptures along a total length of similar to 67 km, is also a nearly pure left-lateral strike-slip fault. The most recent earthquake along this fault is dated to be 7.9-0.5 ka. Combining GPS velocity and active fault kinematics in the northern Tian Shan and western Junggar, we suggest that the western Junggar is controlled by regional N-S crustal shortening related to the India-Eurasia collision, and the reactivated Paleozoic fault zones in the western Junggar play a key role in transferring deformation northeastward into the Altai and Mongolia.