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柯坪推覆系是南天山重要的多排逆断裂推覆系,研究其活动性对讨论天山新生代构造具有重要意义。讨论柯坪推覆系全新世以来的活动特征和古地震情况可以对其最新活动性特点做出评价。通过对柯坪推覆系西段三排褶皱冲断带山前地貌面上断层陡坎的精确测量和典型地点的古地震探槽研究,并通过~(10)Be宇宙成因核素方法确定地貌面时代和古地震发生时间。获得的结果表明全新世以来柯坪推覆系西段的西柯坪塔格断裂、奥兹塔格断裂和托克塔格断裂的活动速率分别为1.45(+1.68/-0.44)mm/a,0.81(+0.35/-0.19)mm/a和(0.3±0.05)mm/a。表现出天山多排逆断层前展模式中活动强度由后排构造向前排构造转移的特点;古地震的位移量和复发周期特点与活动速率相似,前排古地震活动性强于后排,产生较大地表破裂的强震多出现在第一排的柯坪塔格断裂上。其中第一排西柯坪塔格断裂2次地震复发间隔约4 ka,单次地震位移量约3 m;第二排奥兹塔格断裂4次地震复发间隔约2 ka,单次地震位移量约1 m;第三排托克塔格断裂7 ka来仅发生过1次地震。皮羌捩断层是柯坪推覆系东西段前展推覆速率差异的构造结果。推覆系西段的变形速率明显强于东段,造成推覆系统整体沿皮羌捩断层撕裂。同时由于前展模式的构造特点,目前皮羌断裂两侧的后排断层已经存在近20 km的巨大错距,而随着活动速率向前排的转移,前排两侧4km左右的错距正在增大。
The Keping pluton system is an important multi-lateral thrust fault system in southern Tianshan Mountains. It is of great significance to study the activity of Tianshan Mountain in terms of discussing the structure of the Tianshan Cenozoic. Discussing the characteristics of the activities and paleoearthquakes in the area since the Holocene in the Keping area during the Niupo-Nippon-Palaeogeography period can make an assessment on the latest activity characteristics. Based on the accurate measurement of the fault scarp on the front of the three-row fold-thrust belt in the western part of the Keping pluton and the paleoseismic exploration of the typical site, the geomorphology was determined by the ~ (10) Be cosmic formation nuclide method Mian era and the time of the ancient earthquake. The results obtained show that the activities of the Xikapingtag fault, the Ortigas fault and the Tokutag fault in the western part of the Keping pluton are 1.45 (+ 1.68 / -0.44) mm / a, respectively, since the Holocene, 0.81 (+ 0.35 / -0.19) mm / a and (0.3 ± 0.05) mm / a. Showing that the activity intensity in the Tianshan multi-row reverse fault foreland model changed from the rear structure to the front row structure. The displacement and recurrence period of the paleoseismicity are similar to the moving velocity, and the activity of the anterior Paleo- Strong earthquakes that caused large surface ruptures occurred in the first row of the Kepingtage fault. In the first row, the recurrence interval of two earthquakes in Xupingtage fault was about 4 ka with a single seismic displacement of about 3 m. The intervals of the second Ortakay fault in the four earthquakes occurred about 2 ka and the single seismic displacement About 1 m; only 3 earthquakes occurred in the third row of Toktags fracture at 7 ka. The Piqiang fault is the result of the difference in the forward peening rates of the eastern and western segments of the Keping pluton. The deformation rate of the west part of the thrusting system is obviously stronger than that of the eastern part, resulting in the whole of the thrusting system tearing along the faults of the Qiangtang fault. At the same time, because of the tectonic features of the foreground mode, the fault faults in the back faults on both sides of the Piqiang fault nowadays have a huge gap of nearly 20 km. With the transfer of the moving velocity to the front row, the wrong distance of about 4 km on both sides of the front row Increase.