蒙古中南部地区基于天然地震的勒夫波相速度层析成像  

Love wave phase velocity tomography in the south-central Mongolia from earthquakes

作　　者：余大新[1] 吴庆举[2] 王鹏[3] 叶庆东[1] 潘佳铁[2] 高孟潭[2] 

机构地区：[1]中国地震局第一监测中心,中国天津300180 [2]中国地震局地球物理研究所,中国北京100081 [3]水利部长江勘测技术研究所,中国武汉430011

出　　处：《地震学报》2016年第1期41-52,157,共12页Acta Seismologica Sinica

基　　金：中蒙国际科技合作专项(2011DFB20210);国家自然基金(41274088;41504073);中国地震局第一监测中心主任基金(2015014)联合资助

摘　　要：借助中蒙国际科技合作项目获取的宽频带地震台阵观测数据,采用小波变换频时分析技术提取了蒙古中南部地区901条双台间基阶勒夫波相速度频散曲线.通过对该曲线进行二维反演,重构了蒙古中南部地区12—80s周期内横向分辨率约为50km的勒夫波相速度分布图.结果显示,蒙古中南部地区相速度分布存在一定的横向不均匀性.短周期内(12—20s),相速度分布受地表地形的控制,杭爱—肯特山盆表现为高速异常,乌兰巴托盆地、中戈壁带及南戈壁带均表现为低速异常;中等周期内(20—40s),研究区相速度分布形态与短周期类似,但横向不均匀性强度减弱;中长周期内(40—70s),南戈壁带和杭爱—肯特山盆为低速异常,中戈壁带为高速异常,整个区域表现出南北低速异常夹中部高速异常的形态,与瑞雷波中长周期速度分布形态显著不同.结合中戈壁带分布大量新生代火山岩,推测研究区域内存在较强的径向各向异性.This paper utilized the data from broadband seismic arrays of theChina-Mongolia cooperative project, and extracted the fundamental mode Love wave phase velocity dispersion curves along the 901 two-station paths in the south-central Mongolia by the wavelet transformation method. These phase velocity dispersion curves were applied to construct the 2-D Love wave phase velocity maps for the period range of 12-80 s with horizontal resolution about 50 km in the area. The distribution of phase velocity show that horizontal heterogeneity exists in the studied area. The phase velocity distributions at shorter periods （12-20 s） are obviously controlled by geologic units, for exam- ple, Hangay-Hentiy mountain basin exhibits high velocity anomaly while Ulaanbaatar basin, middle Gobi and southern Gobi desert exhibit low velocity anomaly. In the period range of 20-40 s, the features of phase velocity distribu- tion are similar to those for shorter periods, but the amplitude of horizontal heterogeneity becomes weaker. At longer periods （40-70 s）, the southern Gobi and Hangay Hentiy mountain basin show low velocity anomaly while the middle Gobi shows high velocity anomaly, which is distinctly different from that by Rayleigh wave phase tomography. The whole areas present the shape of low velocity anomaly in north and south and high velocity anomaly in middle. Therefore, combined with broad distribution of Cenozoic volcanic rocks in the middle Gobi, it is deduced that the stronger radial anisotropy exists in the studied area.

关 键 词：蒙古中南部 相速度 面波层析成像 勒夫波 

分 类 号：P315.31[天文地球—地震学]