青藏高原北缘三危山断裂晚第四纪以来的左旋走滑活动  

LATE QUATERNARY SINISTRAL STRIKE-SLIP ACTIVITIES OF SANWEI SHAN FAULT IN THE NORTH OF TIBETAN PLATEAU

作　　者：云龙 杨晓平[2] 宋方敏[2] 王驹[1] 

机构地区：[1]核工业北京地质研究院,中核高放废物地质处置评价技术重点实验室,北京100029 [2]中国地震局地质研究所,活动构造与火山重点实验室,北京100029

出　　处：《地震地质》2016年第2期434-446,共13页Seismology and Geology

基　　金：国家自然科学基金(41572195);“甘肃北山旧井地区活动断裂的形成及其地震危险性评价”项目共同资助

摘　　要：通过对三危山断裂沿线微地貌的实地调查,发现山前主要分布2期冲洪积扇,多呈上叠式排布。对比区域冲洪积扇的分布和形成年龄,结合文中的光释光测年（OSL）结果,认为三危山山前老冲洪积扇形成于晚更新世晚期至全新世早期。发育于冲洪积扇上的纹沟、断裂通过的山脊被同步左旋位错,最大和最小位错量分别为5.5m和1.7m,但大多分布在3.0~4.5m之间。结合光释光测年（OSL）结果,得出三危山断裂在距今1.4万a和2.0万a以来的左旋走滑速率分别为（0.33±0.04）mm/a和（0.28±0.03）mm/a。Sanwei Shan Fault is located in the north of Tibet,which is a branch of eastern segment of Altyn Tagn fault zone. This fault is distributed along the boundary of fault facet and the Quaternary,with the total length of almost 150 km. The fault is a straight-line structure read from the satellite image. Based on the spatial distribution of the fault,three segments are divided,namely,Xishuigou-Dongshuigou segment,Dongshuigou-West Shigongkouzi segment and West Shigongkouzi-Suangta segment,these three segments are distributed by left or right step.Though field microgeomorphology investigation along Sanwei Shan Fault,it has been found that two periods of alluvial-pluvial fans are distributed in front of Sanwei Shan Mountain,most of which are overstepped. Comparing the distribution of alluvial- pluvial fans with their formation age in the surrounding regions,and meanwhile,taking the results of optical stimulated luminescence（ OSL）dating,it＇s considered that the formation age of the older alluvial-pluvial fans,which are distributed in northern Qilian Shan,inside of Hexi Corridor and western Hexi Corridor（ including the Sanwei Shan piedmont fans）,is between later period of late Quaternary and earlier period of Holocene. The gullies on the older fan and ridges have been cut synchronously. The maximum and minimum sinistral displacement is 5. 5m and 1. 7m,but majority of the values is between 3. 0 ~ 4. 5m. Taking the results from the OSL dating,we conclude that the minimum sinistral strike-slip rate is（ 0. 33± 0. 04） mm / a since 14 ka BP and（ 0. 28±0. 03） mm / a since 20 ka BP.

关 键 词：晚更新世 左旋走滑 三危山断裂 阿尔金断裂带 青藏高原北缘 

分 类 号：P315.2[天文地球—地震学]