摘要
祁连造山带位于青藏高原东北缘,中祁连地块位于祁连造山带的中心地带,在区域构造演化中占据着重要地位。为揭示祁连造山带地壳速度结构,探讨速度结构与地震活动性之间的关系,本研究利用中国地震台网中心在甘肃、青海等台网记录到的P波、S波到时数据,应用双差层析方法对研究区内6617个地震事件进行重定位,并获得三维P波、S波速度结构及波速比分布。双差成像结果表明:(1)中北祁连断裂带活动性具有东西分段特征,东段以浅层断裂为主(0~10 km),西段存在更深层的构造活动(15~25 km),表明祁连造山带西段上地壳增厚更加显著;大地震集中分布在中上地壳高速异常区域,指示脆性地壳更容易发生断层破裂。(2)速度结构及波速比分布同时呈现纵向的高至低转变过程,表明祁连造山带中上地壳更硬,中下地壳可能存在含水矿物的脱水反应。(3)中祁连地块与北祁连造山带在中上地壳存在显著的界面分隔,与祁连造山带沉积岩层厚度的南深北浅分布特征有较好对应。
The Qilian Orogenic Belt,located at the northeastern margin of the Tibetan Plateau with the Central Qilian Block at its core,plays a significant role in regional tectonic evolution.To reveal the crustal velocity structure of the Qilian Orogenic Belt and investigate the relationship between velocity structure and seismic activity,this study utilized P-wave and S-wave arrival time data recorded by seismic networks in Gansu,Qinghai,and other regions under the China Earthquake Networks Center.A double-difference tomography method was applied to relocate 6,617 seismic events in the study area,and 3D P-wave/S-wave velocity structures as well as velocity ratio distributions were obtained.The double-difference tomography produced several interesting results:(1)The Central-Northern Qilian Fault Zone exhibits distinct segmentation in activity along its eastern and western sectors.The eastern segment is dominated by shallow-seated faulting(0-10km),whereas the western segment features deeper-seated tectonic activity(15-25km).This indicates more pronounced upper crustal thickening in the western sector of the Qilian orogenic belt.Large earthquakes are concentrated in high-velocity anomaly regions of the upper-middle crust,suggesting that brittle crust is more prone to fault rupture.(2)Both velocity structures and velocity ratio distributions show a vertical transition from high to low values,indicating that the upper-middle crust of the Qilian Orogenic Belt is more rigid,whereas the middle-lower crust may include dehydration reactions of hydrous minerals.(3)There is a significant interface separation between the Central Qilian Block and the North Qilian Orogenic Belt in the upper–middle crust,which corresponds well with the south-deep and north-shallow distribution characteristics of sedimentary rock layer thickness in the Qilian Orogenic Belt.
作者
梁赐安
沈旭章
李敏娟
刘谨瑞
LIANG Ci'an;SHEN Xuzhang;LI Minjuan;LIU Jinrui(School of Earth Sciences and Engineering,Sun Yat-sen University,Zhuhai 519000,China;Gansu Earthquake Agency,Lanzhou 730000,China)
出处
《CT理论与应用研究(中英文)》
2025年第5期763-774,共12页
Computerized Tomography Theory and Applications
基金
国家自然基金重点项目(祁连造山带深部结构与晚新生代构造变形研究(42230305))
2025年度地震预测开放基金(XH25005D)。
关键词
祁连造山带
双差层析成像
地壳速度结构
Qilian orogenic belt
double-difference tomography
crustal velocity structure
