Abstract: The Longling-Ruili Fault is an important northeast trending active fault in southwestern China which controls the development of the sedimentary series and magmatic action of the two sides of the fault,and also controls Longling Basin,Mangshi Basin and Zhefang Basin along the fault.Due to limited Quaternary sediments samples and harsh natural conditions,the study of late Quaternary fault activity on the northern segment of the Longling-Ruili Fault is lacking and presently the time of the newest faulting and the Quaternary slip rate are not clear.Based on interpretation of remote sensing images,quantitative geomorphologic deformation measurement and dating of young terrace deposits and alluvial fans,the paper obtains some new results as follows:The northern segment of Longling-Ruili Fault is a Holocene dextral strike-slip fault with a normal slip component.The terrace T1 composed mainly of alluvial deposits formed during 4ka BP was offset by the northern segment of the Longling-Ruili Fault,with left-lateral and vertical displacements of 8～12m and 2m,respectively.The late Pleistocene alluvial fan was dislocated with a left-lateral and vertical displacement of 70m and 18m,respectively.The strike-slip rate of the Longling-Ruili Fault is 2.2～2.5mm/a and vertical slip rate is 0.6mm/a since late Pleistocene epoch.The strike-slip rate of the Longling-Ruili Fault is 1.8～3.0mm/a and vertical slip rate is 0.5mm/a during the Holocene epoch.The proportion of horizontal to vertical displacement is about 4:1,that means the vertical rate on the northern segment of Longling-Ruili Fault is about 25%of horizontal slip rate.The left-lateral slip rate in late Holocene is well consistent with GPS measurement.The strike slip rate is in good consistency in different time scales since late Pleistocene epoch,indicating that the activity of the Longling-Ruili Fault is stable.

Key words: the Longling-Ruili Fault, late Quaternary, faulted landforms, slip rate

摘要： 遥感影像解译和野外地质地貌调查表明,龙陵-瑞丽断裂(南支)北段是以左旋走滑为主兼张性正断的区域性活动断裂。根据一些断错地貌点的大比例尺填图、实地测量及其年代学分析,确定了该断裂为全新世活动断裂,断裂晚更新世以来的平均水平滑动速率为2.2mm/a,平均垂直滑动速率为0.6mm/a;全新世以来的平均水平滑动速率为1.8～3.0mm/a,平均垂直滑动速率为0.5mm/a。断裂晚更新世以来的滑动速率在不同的时间尺度上变化不大,反映了该断裂晚更新世以来的活动强度比较平稳。

关键词: 龙陵-瑞丽断裂, 晚第四纪, 断错地貌, 滑动速率