河西走廊地质构造基本特征以及榆木山北麓与黑河口上龙王活断层研究

作者对河西走廊活动构造尤其是其中段榆木山北麓与黑河口上龙王活断层进行了详细考察和研究,得出下列几点认识: (1) 祁连山山脉是一个向东北推进的推覆体构造,估计其向东北推进的距离在中更新世以来约4—5公里;(2) 在榆木山北麓的北西西向断层带以逆掩断层为主,断层切割的最新地层为晚更新世晚期地层,並保存有古地震遗迹,估计其最新一次古地震的时代距今约1—2万年;(3) 黑河口上龙王北北西向右旋断层切割的最新地层为晚更新世末期砾石层,据槽探揭露与地貌分析,该断层右旋断开黑河四级阶地20多米,並保存有距今最近的四次古地震遗迹。其震级约7—8级。据(14)C测定,后两次古地震分别在15700年与13300年。前两次古地震的时代估计在25000年和24500年左右。其重复间隔大者为8800年左右,小者为2400年和500年左右。

RESEARCH ON THE FUNDAMENTAL CHARACTERISTICS OF THE GEOLOGICAL STRUCTURES OF THE HEXI CORRIDOR AND THE ACTIVE FAULTS OF THE NORTHERN AND EASTERN FLANK OF THE YUMUSHAN MOUNTAIN

In this paper, the fundametal characteristics of the geological structures of the Hexi corridor basin and the recently active features of the fault at the northern flank of the yumushan mountain and Shanglongwang fault at the eastern flank of the yumushan mountain in its middle segment have been discussed. The research result has indicated that(1) The Qilian mountain range is a nappe that moves to the northeastwards. It is estimated that the distance moving to the northeastwards is abont 4-5 kilometers since the middle Pleistocene.(2) The NWW fault belt located at the north flank of Yumushan mountain takes overthrust as the dominant factor and cuts the deposits of the later part of the late Pleistocene.(3) The activity type of the NNW Shanglongwang fault belongs to the type of the right strike slip accompany with the pressure. The geologicol and micro geomorphic evidences show that there have occurred 4 times earthquakes with the magnitude 7-8 in this fault since 25000yr. ago, and the latest one of them occurred at about 13300yr. ago. About the reoccurrence interval of the 4 times paleothquakes, they are nonuniform, namely, there are either the big or the small interval in this fault.