【摘要】 三危山断裂位于青藏高原北缘,为阿尔金断裂带的一条重要分支,研究其晚更新世以来的活动特征,可为全面地把握青藏高原北缘的地震活动规律提供基础资料。在对三危山断裂东北段(十工口子西-双塔)进行遥感资料解译、野外地质地貌调查和探槽开挖,并分析探槽内揭露的断层、地层和楔状堆积三者之间关系的基础上,结合相关堆积物的光释光断代研究,最终利用逐次限定法分析了古地震事件发生的年代。研究发现该断裂段上晚更新世以来发生了3次古地震事件:距今最远的一次事件E1发生在约5.3万年前,接近5.3万年;第二次事件E2发生于距今约4万年之前,5.3万年之后,更接近4万年;最近的一次事件E3发生于距今7.42—2.47ka。由于晚更新世以来探槽开挖地点地层沉积的不连续,或地层沉积之后发生的侵蚀作用,导致探槽内揭露出的古地震事件存在严重缺失。但可以确定的是,在晚更新世中晚期和全新世,三危山断裂东北段上确有破裂地表的古地震事件发生。更多还原

【Abstract】 The Sanweishan Mountain fault, located in the north of Tibetan Plateau, is an important branch of Altyn Tagh fault. For providing the basic information to understand the regulation of seismic activity roundly in the north of Tibetan Plateau, we focus on the activity characteristic since late Pleistocene of Sanweishan Mountain fault. The remote sensing data, field investigation and trenches measurement along the northeastern segment(South of Shigongkouzi-Shuangta) on piedmont fault of Sanweishan Mountain. Meanwhile, we analyze paleo-earthquake events using the relationship between faults, stratums, and wedge-shaped deposit, dating some accumulation samples for related to fault activity, and confining the occurred time of paleo-earthquake events by progressive constraining method. The results show that three paleo-earthquake events have occurred along the northeastern segment of Sanweishan Mountain fault since late Pleistocene. The oldest event E1 occurred before about 53 ka B.P., and the second event E2 occurred between 53 ka and 40 ka B.P., and the latest event E3 occurred between 7.42 ka and 2.47 ka B.P. The depositional discontinuity of stratums, or erosion after stratums deposited around the trench site since the late Pleistocene, lead to the serious lack of paleo-earthquake event record, but it is for sure that paleo-earthquake events, which ruptured surface, occurred along the northeastern segment of Sanweishan Mountain fault during mid-late Pleistocene and Holocene.更多还原