Abstract: Strike-slip fault plays an important role in the process of tectonic deformation since Cenozoic in Asia. The role of strike-slip fault in the process of mountain building and continental deformation has always been an important issue of universal concern to the earth science community. Junggar Basin is located in the hinterland of Central Asia, bordering on the north the Altay region and the Baikal rift system, which are prone to devastating earthquakes, the Tianshan orogenic belt and the Tibet Plateau on the south, and the rigid blocks, such as Erdos, the South China, the North China Plain and Amur, on the east. Affected by the effect of the Indian-Eurasian collision on the south of the basin and at the same time, driven by the southward push of the Mongolian-Siberian plate, the active structures in the periphery of the basin show a relatively strong activity. The main deformation patterns are represented by the large-scale NNW-trending right-lateral strike-slip faults dominated by right-lateral shearing, the NNE-trending left-lateral strike-slip faults dominated by left-lateral shearing, and the thrust-nappe structure systems distributed in piedmont of Tianshan in the south of the basin. There are three near-parallel-distributed left-lateral strike-slip faults in the west edge of the basin, from the east to the west, they are:the Daerbute Fault, the Toli Fault and the Dongbielieke Fault. This paper focuses on the Dongbielieke Fault in the western Junggar region. The Dongbielieke Fault is a Holocene active fault, located at the key position of the western Junggar orogenic belt. The total length of the fault is 120km, striking NE. Since the late Quaternary, the continuous activity of the Dongbielieke Fault has caused obvious left-lateral displacement at all geomorphologic units along the fault, and a linear continuous straight steep scarp was formed on the eastern side of the Tacheng Basin. According to the strike and the movement of fault, the fault can be divided into three segments, namely, the north, middle and south segment.
In order to obtain a more accurate magnitude of the left-lateral strike-slip displacement and the accumulative left-lateral strike-slip displacement of different geomorphic surfaces, we chose the Ahebiedou River in the southern segment and used the UAV to take three-dimensional photographs to obtain the digital elevation model(the accuracy is 10cm). And on this basis, the amount of left-lateral strike-slip displacement of various geological masses and geomorphic surfaces(lines)since their formation is obtained. The maximum left-lateral displacement of the terrace T₅ is(30.7±2.1)m and the minimum left-lateral displacement is(20.1±1.3)m; the left-lateral displacement of the terrace T₄ is(12±0.9)m, and the left-lateral displacement of the terrace T₂ is(8.7±0.6)m. OSL dating samples from the surface of different level terraces(T₅, T₄, T₂ and T₁)are collected, processed and measured, and the ages of the terraces of various levels are obtained. By measuring the amount of left-lateral displacements since the Late Quaternary of the Dongbielieke Fault and combining the dating results of the various geomorphic surfaces, the displacements and slip rates of the fault on each level of the terraces since the formation of the T₅ terrace are calculated. Using the maximum displacement of(30.7±2.1)m of the T₅ terrace and the age of the geomorphic surface on the west bank of the river, we obtained the slip rate of(0.7±0.11)mm/a; similarly, using the minimum displacement of(20.1±1.3)m and the age of the geomorphic surface of the east bank, we obtained the slip rate of(0.46±0.07)mm/a. T₅ terrace is developed on both banks of the river and on both walls of the fault. After the terraces are offset by faulting, the terraces on foot wall in the left bank of the river are far away from the river, and the erosion basically stops. After that, the river mainly cuts the terraces on the east bank. Therefore, the west bank retains a more accurate displacement of the geomorphic surface(Gold et al., 2009), so the left-lateral slip rate of the T₅ terrace is taken as(0.7±0.11)mm/a. The left-lateral slip rate calculated for T₄ and T₂ terraces is similar, with an average value of(0.91±0.18)mm/a. In the evolution process of river terraces, the lateral erosion of high-level terrace is much larger than that of low-level terrace, so the slip rate of T₄ and T₂ terraces is closer to the true value. The left-lateral slip rate of the Dongbielieke Fault since the late Quaternary is(0.91±0.18)m/a. Compared with the GPS slip rate in the western Junggar area, it is considered that the NE-trending strike-slip motion in this area is dominated by the Dongbielieke Fault, which absorbs a large amount of residual deformation while maintaining a relatively high left-lateral slip rate.

Key words: western Junggar, Dongbielieke Fault, deformation of terrace, slip rate

摘要： 冬别列克断裂是一条全新世活动断裂，位于西准噶尔造山带的关键位置，该断裂总长120km，走向NE。晚第四纪以来，冬别列克断裂的持续活动使得断裂沿线各级地貌面发生了明显的左旋位错，在塔城盆地东侧形成线性连续且笔直的陡坎地貌。文中利用高精度无人机和差分GPS对阿合别斗河多级阶地的左旋位错量进行了面状航拍、测量，建立了分辨率高达0.1m的数字地形数据，发现T₅-T₂阶地陡坎的最大左旋位错量依次为30.7m、12.0m和8.7m。通过光释光测年方法得到了各级阶地（T₅-T₁）的年龄，进而得出冬别列克断裂晚更新世以来的左旋滑动速率为0.7~0.94mm/a，结合阶地侧向侵蚀特征，分析认为T₄、T₂阶地的滑动速率更加接近真实值（0.91±0.18）mm/a。结合西准噶尔的其它2条大型走滑断裂（达尔布特断裂和托里断裂）的滑动速率，并对比西准噶尔地区的GPS速率，认为该地区NE向的走滑运动以冬别列克断裂为主，吸收大量剩余变形，同时保持相对较高的左旋滑动速率。

关键词: 西准噶尔, 冬别列克断裂, 阶地位错, 滑动速率