青藏块体北部金塔南山断裂晚第四纪走滑活动的地质地貌特征  

GEOLOGICAL AND GEOMORPHIC EXPRESSIONS OF LATE QUATERNARY STRIKE-SLIP ACTIVITY ON JINTA NANSHAN FAULT IN NORTHERN EDGE OF QING-ZANG BLOCK

作　　者：张波[1,2] 何文贵[1] 庞炜[3] 吴赵[1] 邵延秀[1,2] 袁道阳[1] 

机构地区：[1]中国地震局兰州地震研究所,兰州730000 [2]中国地震局地质研究所,北京100029 [3]中国地震局第二监测中心,西安710054

出　　处：《地震地质》2016年第1期1-21,共21页Seismology and Geology

基　　金：中国地震局地震预测研究所基本科研业务专项(2013IESLZ07)资助

摘　　要：前人对位于青藏块体北部与阿拉善块体接触带的金塔南山断裂是否存在左旋走滑新活动一直存在争议。文中基于航空照片和高分辨率遥感影像解译、地质地貌调查与填图、差分GPS测图、开挖剖面等方法,详细研究了金塔南山断裂的地质、地貌表现,分析是否存在左旋走滑的新活动特征。结果表明:金塔南山断裂晚第四纪以来有左旋走滑活动,地貌上表现为正、反向交替的断层陡坎、冲沟和微地貌的左旋位错、拉分盆地和挤压隆起等现象;地质剖面上表现为高倾角的断层面、倾向和性质不固定的断层面、花状构造。通过对比分析,得到金塔南山断裂晚更新世以来的左旋走滑速率约为(0.19±0.05)mm/a,与倾滑速率以及地表抬升速率相当,但远小于阿尔金断裂的走滑速率。综合分析认为,祁连山逆冲断裂系向NE的挤压扩展与应变分配可能是金塔南山断裂左旋走滑运动的动力学来源。Jinta Nanshan Fault is an important fault in northeast front of Qing-Zang Plateau,and it is crucial for determining the eastern end of Altyn Tagh Fault. However,there is still debate on its significant strike-slip movement.In this paper,we study the Late Quaternary activity of Jinta Nanshan Fault and its geological and geomorphic expressions by interpreting aerial photographs and high-resolution remote sensing images,surveying and mapping of geological and geomorphic appearances,digging and clarifying fault profiles and mapping deformation characteristics of micro-topographies,then we analyze whether strike-slip activity exists on Jinta Nanshan Fault.We get a more complete fault geometry than previous studies from most recent remote sensing images. Active fault traces of Jinta Nanshan mainly include 2 nearly parallel,striking 100° ~ 90°fault scarps,and can be divided into 3 segments. West segment and middle segment form a left stepover with 2 ~ 2. 5km width,and another stepover with 1. 2km width separates the middle and east segment.We summarize geomorphic and geologic evidence relating to strike slip activity of Jinta Nanshan Fault. Geomorphic expressions are as follows： First,fault scarps with alternating facing directions;second,sinistral offset of stream channels and micro-topographies; third, pull-apart basins and compressive-ridges at discontinuous part of Jinta Nanshan Fault. Geologic expressions are as follows：First,fault plane characteristics,including extremely high fault plane angle,unstable dip directions and coexistence of normal fault and reverse fault; second,flower structures.Strike-slip rate was estimated by using geomorphic surface age of Zheng et al.（ 2013） and left-lateral offset with differential GPS measurements of the same geomorphic surface at field site in Fig.4e. We calculated a strike-slip rate of（ 0. 19±0. 05） mm / a,which is slightly larger than or almost the same with vertical slip rate of（ 0. 11±0. 03） mm / a from Zheng et al.（ 2013）.When we confirm the strik

关 键 词：金塔南山断裂 左旋走滑 滑动速率 

分 类 号：P315.2[天文地球—地震学]