青藏高原中部五道梁-曲麻莱断裂系西段晚第四纪滑动速率厘定

五道梁-曲麻莱断裂系位于青藏高原中部,关于其晚第四纪活动性迄今鲜有介绍。由高分辨率卫星影像解译和野外地质考察可知,断裂系西段由五道梁南山北缘断裂和五道梁南山南缘断裂组成,二者分别断错了五道梁南山两侧的各级洪积扇。通过洪积扇上的断错地貌分析和光释光测年方法得到南缘断裂缩短速率为（0.25±0.11）mm/a,北缘断裂缩短速率为（0.50±0.05）mm/a。基于经验公式和最新洪积扇上陡坎高度,推测南、北缘断裂可能曾发生7.2～7.4级地震,大震复发周期长达8 000余年;如果陡坎高度由2次古地震事件叠加形成,则可能发生6.9～7.1级地震,全新世中期以来大震复发周期可能为2 000～3 000年。

Late Quaternary Slip Rates along Western Segment of the Wudaoliang-Qumalai Fault System in Central Tibet

The Wudaoliang-Qumalai fault system is located in the central of Qinghai-Tibet Plateau, and little is known about its activity since Late Quaternary. Based on high-resolution satellite image interpretation and field investigation, it can be seen that Wudaoliang southern mountain faults is composed of the northern margin fault of Wudaoliang southern mountain and the southern margin fault of Wudaoliang southern mountain. The two faults displaced new diluvial fans on both sides of the Mountain. We used unmanned aerial vehicle topographic surveying and OSL dating of offset diluvial fans to characterize shortening rate along western segment of the Wudaoliang-Qumalai fault system being 0.25±0.11 mm/a and 0.50±0.05 mm/a, respectively. Fault displacement on newest fan and scaling relationships imply that the most recent earthquake was approximately M7.2～7.4 with a recurrence period of more than 8 000 years. If there were two events on the fans, the events were M6.9～7.1 with the recurrence period during 2000～3000 years since the middle Holocene.