嘉黎断裂带中段流域地貌形态指数与新构造活动特征  

Geomorphic Index and Activity Characteristics of the Mid-Segment of Jiali Fault

作　　者：黄峰 熊仁伟[1] 林敬东 赵峥 杨攀新[1] HUANG Feng;XIONG Ren-wei;LIN Jing-dong;ZHAO Zheng;YANG Pan-xin(Institute of Earthquake Forecasting,CEA,Beijing 100036,China)

机构地区：[1]中国地震局地震预测研究所,北京100036

出　　处：《地震》2024年第1期1-18,共18页Earthquake

基　　金：中国地震局地震预测研究所基本科研业务费专项(2018IEF010101,CEAIEF2022030201)。

摘　　要：本文以嘉黎断裂带中段(尼屋乡—古乡段)为研究对象,利用30 m分辨率的SRTM DEM数据,提取435条支流流域标准化陡峭指数(ks)、 43条支流河谷宽高比指数(VF)、 55个流域面积-高程积分指数(HI)、 10条支流河道纵剖面和裂点。依据不同河段的河流标准化陡峭指数和沿河道纵向剖面的一系列裂点分布特征,将研究区划分出流域上游、下游南侧与下游北侧三个区域进行对比分析。上游ks值与HI值均低于下游,而VF值高于下游。这些数据研究结果表明,尼屋乡—古乡段下游区域构造抬升活动强烈,而上游区域抬升则相对较弱。尼屋乡—古乡段下游选取南北两侧各5条支流分析,遥感解译结果显示断裂大致沿河谷南侧展布,多与南侧一级支流低海拔裂点发育位置相当。结合野外断裂剖面调查和测年结果分析,认为断裂中段活动时代为全新世早期或晚更新世晚期,除右旋走滑活动外,还伴有显著的逆冲挤压性质,其原因是断裂中段位于青藏高原东构造结正北侧,推测断裂除羌塘块体向东运移影响外,逆冲作用是受构造节持续向北推挤作用的结果。435 tributary basin standardised steepness indices(k,),43 tributary valley width-height ratio(VF),55 basin area-elevation integral index(HI),10 tributary channel longitudinal profiles and knick points were extracted by using 30 m resolution SRTM DEM data for the middle section of the Jiali Fracture Zone(Niwuxiang-Guxiang).Based on the river steepness indices of different reaches and the distribution characteristics of a series of knick points along the river longitudinal profile,the study area was divided into three are-as for comparative analysis:upstream,the south side and the north side of the lower part.The upstream k,and HI were lower than the downstream values,while the VF values were higher than the downstream values.The study results indicated that the tectonic up-lift activity in the downstream area of the middle section of the fault was strong,while the uplift in the upstream area was relatively weak.Five tributaries from the north and south were selected respectively for analysis in the downstream part of the Niwuxiang-Guxiang section,and the remote sensing interpretation results showed that the fracture spread roughly along the southern side of the river valley,and was mostly in the same position as the development of low elevation knick points of the first-order tributaries on the southern side.Combining with the results of the field fracture profile survey and dating result,the analysis suggested that the middle section of the fracture was of early Holocene or Late Pleistocene age,and was accompanied by significant recoil extrusion in addition to right-slip activity.The reason was that the middle section of the fault was located directly north of the eastern tectonic junction of the Qinghai-Xizang Plateau,and it was assumed that in addition to the eastward transport of the Qiangtang block,the recoil was the result of the continuous northward pushing of the tectonic junction.

关 键 词：地貌指数 河流纵剖面 嘉黎断裂 新构造运动 

分 类 号：P315.7[天文地球—地震学]