Abstract: The Boluokenu fault is the boundary between the north and middle Tianshan, and has many periods of activity. Microgeomorphology related to fault activity, gully right-lateral displacement, fault scarp, pull apart basin occur along the fault in the southeast of Jinghe county town to Alashankou. Large gullies on the alluvial-pluvial fan are cut by the Boluokenu fault, the largest right-lateral displacement is about 500m, and its average is 400m. Some small gullies which only developed on the fault scarp have been cut by the fault. Its right lateral displacement can be divided into four groups in displacement values, i.e. 2.4～4.0m, 5.7m, 8.3m and 15.3m. The height of the fault scarp can be divided into three groups of which the value is 1.2m, 2.51m and 3.63m, respectively. In the southwest of Alashankou, right-lateral displacement for small gullies is 1～1.7m. The heights of the fault scarp on deferent geomorphic surface are 0.55m and 1.2～1.5m. All these didplacement values may indicate that the horizontal and vertical displacement of characteristic earthquakes on the segment is 3m and 1.2m, respectively. The age of the alluvial-pluvial fan in southeast Jinghe is about 70 ka old by geomorphic dating, and the right-lateral slip rate is 4.7mm/a.

Key words: Strike-slip fault, Horizontal displacement, Late Pleistocence, Slip rate, Boluokenu fault

摘要： 通过对博罗可努断裂精河-阿拉山口段微地貌的实地调查,发现该断裂错断精河东南到阿拉山口之间的晚更新世冲洪积扇,地表留下了冲沟和山脊同步右旋位错、断层陡坎、断层鼓包、拉分盆地等与断层活动有关的微地貌。精河东南冲洪积扇上大冲沟的最大右旋位移为500m,平均400m。断层陡坎上的纹沟右旋位移为2.6～4.0m,较大级别的纹沟位移可分为5.7m,8.3m和15.3m3组。它们大致为3的整数倍。实测断层陡坎的高度分别为1.2m,2.51m和3.63m,大致是1.2的整数倍,阿拉山口西南断层的水平位移为1～1.7m;垂直位移可分为两组,一组为0.55m,另一组为1.2～1.5m。这些数据可能揭示了该断裂段的特征地震水平位移为3m,垂直位移为1.2m。区域地貌对比和年代学分析得出,精河东南冲洪积扇的最后形成时代为距今7万a左右,右旋滑动速率为4.7mm/a。

关键词: 走滑断层, 水平位移, 晚更新世, 滑动速率, 博罗可努断裂