Abstract: The newest active time and segmentation of the fault are of special significance in the safety evaluation of major engineering projects.This paper discusses the active times and segmentation characteristics of the Guanguanling Fault zone through interpreting aerial photos,field investigation,topographic and geomorphic surveys and analysis of trench logs on paleoearthquake in connection with the study of the geological and seismologic problems in Heishanxia project of the Huanghe River.The Guanguanling active fault zone lies on the northeastern margin of the Qinghai-Tibet block.It is part of the Zhongwei-Tongxin arc active fault zone,striking near EW generally,with a total length of about 60km.It consists of 5 discontinuous secondary faults arranged in left step en echelon,namely,Jingtaixiaohongshan(F_1-1),Guanguanling(F_1-2),Shajing(F_1-3),Zhongweixiaohongshan(F_1-5)and Qingshan-Gushanzi(F_1-4),respectively.Since Late Quaternary,the fault is characterized with intense sinistral strike-slip and compressional thrust and has offset a series of ridges and small gullies and terraces.At the same time,fault scarps were developed along the fault zone.The study reveals that the latest earthquake occurred 700～1200a BP,the largest displacement took place in Guanguanling,and the maximum horizontal sinistral displacement reaches 6m since Holocene.

Key words: Guanguanling active fault zone, northeastern margin of the Qinghai-Tibet block, neo-activity

摘要： 断层的最新活动时代以及分段特征一直在重大工程安全性评价中具有特别重要的意义。在解决黄河黑山峡地震地质问题时,通过对罐罐岭断裂带的航片解译、野外追踪调查、地形地貌测量和古地震槽探资料研究,从而确定了该断裂带的活动时代以及分段特征。该断裂带发育在青藏块体东北缘,是中卫-同心弧形活动构造带的一部分,总体走向近EW,长约60km,分为5条不连续的次级断层,各段成左阶羽列,晚第四纪以来表现出强烈的左旋走滑兼挤压逆冲活动特征。断层错断了一系列山脊、小冲沟和阶地等,发育醒目的断层陡坎。研究发现,罐罐岭断裂最新一次地震破裂发生在距今700～1200a之间,最大同震位移位于罐罐岭附近,全新世以来水平左旋最大错距达6m。

关键词: 活动断裂, 青藏块体东北缘, 新活动