Tian Shan is a vast and highly seismically active intracontinental mountain range. GPS measurements and field studies have shown that E-W and NW-SE trending thrusts and fault-related folds are distributed across central Tian Shan. However, few studies have determined the fault and fault-related-fold activity in the Bole Basin, the northernmost part of central Tian Shan. In this study, we focus on the Alashak Fold, which is situated along the southern margin of the Bole Basin. Using high-resolution uncrewed aerial vehicle-Digital Elevation Model data, field observations, and detailed mapping, we determined that the Alashak Fold is characterized by a trishear fault-propagation fold. Along the Alashak River, we identified five levels of fluvial surfaces, the T3 terrace was continuously preserved across the fold. Radiocarbon and surficial Be dating were used to determine the exposure age of the deformed T3 terrace. The folding characteristics of T3, trishear inversed modeling, and abandonment age indicate that the Alashak Fault has an uplift rate of 0.8 ± 0.3 mm/yr, a dip-slip rate of 4.2 ± 1.2 mm/yr, and a crustal shortening rate of 4.0 ± 1.2 mm/yr since the late Pleistocene, respectively. The Alashak and Latgan Faults intersect at a depth of 1.2 km, enclosing a wedge-shaped block. Our study emphasizes that tectonic activity along the southern margin of the Bole Basin has played a significant role in north-south shortening within central Tian Shan, as measured by geological measurements since the late Pleistocene. The Alashak Fault can potentially generate moderate–strong (Mw 5.0–7.0) earthquakes, while the Alashak and Latgan Faults can generate major (Mw 7.2) earthquakes.

中文翻译：

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博乐盆地晚更新世断层滑动速率：中天山变形运动学的见解


天山是一片广阔且地震活跃的陆内山脉。 GPS测量和实地研究表明，东西向和西北-东南向的逆冲断层和与断层相关的褶皱分布在天山中部。然而，很少有研究确定中天山最北端博乐盆地的断层和与断层相关的褶皱活动。在这项研究中，我们重点关注位于博乐盆地南缘的阿拉沙克褶皱。利用高分辨率无人驾驶飞行器数字高程模型数据、现场观测和详细测绘，我们确定阿拉沙克褶皱具有三剪断层传播褶皱的特征。沿着阿拉沙克河，我们确定了五层河流表面，T3阶地在褶皱上连续保留。利用放射性碳和地表铍定年法确定了变形T3阶地的暴露年龄。 T3褶皱特征、三剪反演和废弃年龄表明，阿拉沙克断层的隆升速率为0.8±0.3mm/yr，倾滑速率为4.2±1.2mm/yr，地壳缩短速率为4.0自更新世晚期以来，分别为 ±1.2 毫米/年。阿拉沙克断层和拉特甘断层相交深度为 1.2 公里，围成一个楔形断层。我们的研究强调，根据晚更新世以来的地质测量，博乐盆地南缘的构造活动对天山中部南北缩短发挥了重要作用。阿拉沙克断层有可能产生中强（震级5.0-7.0）地震，而阿拉沙克和拉特甘断层则可能产生大地震（震级7.2）。