背景噪声和地震面波联合反演渭河盆地及邻区壳幔S波速度结构  

JOINT INVERSION OF AMBIENT NOISE AND SURFACE WAVE FOR S-WAVE VELOCITY OF THE CRUST AND UPPERMOST MANTLE BENEATH WEIHE BASIN AND ITS ADJACENT AREA

作　　者：冯红武 颜文华 严珊[1] 郭瑛霞 惠少兴[1] 常城 FENG Hong-wu;YAN Wen-hua;YAN Shan;GUO Ying-xia;HUI Shao-xing;CHANG Cheng(Shaanxi Earthquake Agency,Xi'an 710068,China;Jiangsu Earthquake Agency,Nanjing 210014,China)

机构地区：[1]陕西省地震局,西安710068 [2]江苏省地震局,南京210014

出　　处：《地震地质》2019年第5期1185-1205,共21页Seismology and Geology

基　　金：中国地震局地震科技星火计划项目(XH17035YSX);陕西省地震局启航与创新基金(QC201923)共同资助

摘　　要：利用陕西及邻区测震台网和中国地震科学台阵探测项目共257个宽频带台站记录的连续波形与远震数据,采用基于射线追踪的面波频散直接反演方法获得了渭河盆地及邻区地壳上地幔顶部S波速度结构,成像结果显示:1)渭河盆地顶部形成于新生代的沉积层造成其浅部显著的低速异常,盆地中、上地壳为低速结构,低速带延深至约25km深处,莫霍面相对两侧突变上隆,上地幔高速体侵入下地壳,可能与中-新生代上地幔基性-超基性铁镁质物质底侵有关。2)南鄂尔多斯块体地壳浅层东薄西厚的低速结构可能与块体遭受的整体掀斜、差异性抬升和强烈而不均匀的剥蚀有关。壳内不存在明显的低速异常,说明壳内低速体并没有贯穿整个鄂尔多斯地块,鄂尔多斯南段仍保留着稳定克拉通属性,至今还未遭受明显改造。3)秦岭造山带东、西深部结构存在差异,具有分段特征。造山带下地壳底部的低速异常,可能与造山带受青藏高原东北缘隆升和向外扩展等构造活动的影响有关,分析认为秦岭造山带存在青藏高原物质E流的下地壳流通道的可能性不大。The Weihe Basin is the main component of the extrusion and escape shear zone between the ancient North China craton block in Ordos and the ancient Yangtze platform in Sichuan Basin,and carries the dynamic transmission from the main power source of the Qinghai-Tibet Block in the west to the North China and South China regions in the east. The basin itself plays multi roles in the east-west and north-south tectonic movement,and is an excellent site for studying the structural interlacing,dynamic transformation and transmission. At the same time,Weihe Basin is also a famous strong earthquake zone in China. Historically,there was a strong earthquake of magnitude 81/4 occurring in Huaxian County in 1556,causing huge casualties and property losses. In view of the special geological structures and the characteristics of modern seismicity activities in the Weihe fault-depression zone,it is necessary to carry out fine three-dimensional velocity structure detection in the deep part of Weihe Basin and its adjacent areas,so as to study the relationship between velocity structure and geological structural units and their evolution process,as well as the deep medium environment where earthquakes develop and occur.We investigate the S-wave velocity structure beneath Weihe Basin and its adjacent regions based on continuous background noise data and teleseismic data recorded by 257 broadband stations in Shaanxi Province and its adjacent regions and China Seismological Science Array Exploration Project,and by adopting seismic surface wave inter-station method and background noise cross-correlation method,a total of 10 049 fundamental-mode Rayleigh surface wave phase velocity dispersion curves in the periods of 5 ~ 70 s are obtained. Firstly,using the average dispersion curve in this study area,we obtain the one-dimensional average S-wave velocity structure model of the study area,and then we apply the ray-tracing surface-wave-dispersion direct inversion method to obtain the S-wave velocity structure of the crust and uppermost mant

关 键 词：背景噪声 地震面波 S波速度结构 渭河盆地 频散曲线 

分 类 号：P315.31[天文地球—地震学]