广东及其邻域噪声面波层析成像  

Surface wave tomography of Guangdong and its adjacent areas from ambient seismic noise

作　　者：沈玉松[1,2] 康英[2] 

机构地区：[1]中国科学技术大学地球与空间科学学院,中国合肥230026 [2]广东省地震局,中国广州510070

出　　处：《地震学报》2014年第5期826-836,980,共11页Acta Seismologica Sinica

基　　金：广东省科技计划项目(20090308);地震公益性行业科研专项(201308008);地震科技星火计划(XH13019)共同资助

摘　　要：通过收集广东及其邻域104个固定地震台站近10个月的垂直分量连续波形数据资料,使用地震背景噪声互相关格林函数方法,获得了大部分台站对的背景噪声互相关曲线.基于这些对称叠加的互相关曲线,利用时频分析方法,进一步提取了该地区周期为5—40s的基阶瑞雷波群速度频散曲线.其噪声来源分析结果显示:广东及其邻域的噪声场来源有很强的方向性,短周期(5—10s)噪声主要来自东南方向,范围基本与海岸线分布一致,可能是由于近海水陆相互作用产生的;较长周期(15—30s)噪声主要来自三大洋的方位.以这些提取的噪声面波资料为基础,采用噪声面波层析成像方法反演得到了该地区周期为5—28s的瑞雷波群速度层析成像图,从该图可以看出,广东及其邻域地下结构的横向变化总体较小,沉积层厚度较薄,地壳中可能普遍存在一个低速层;从研究区历史地震的分布及其表层地质构造的发育特征来看,地震主要分布在高、低速过渡带附近,表明面波群速度与地震之间具有较强的耦合关系;从群速度的低速异常特征来看,广东及其邻域普遍分布的温泉和高地热主要受深部构造的控制和影响.We obtain the ambient noise cross-correlation curves for most of the station-pairs using 10 months of continuous data from the 104 permanent seis-mic stations of the Guangdong seismic network and its surrounding regions. Based on these symmetrically superimposed cross-correlation curves,we com-plete Rayleigh wave group velocity dispersion measurements for the periods from 40 s down to about 5 s using time-frequency analysis method.Ambient noise source analyses show that in Guangdong and its neighbor areas,sources of noise field has a strong directionality.Short-period noise （5-10 s）is mainly from the southeast,and its distribution is consistent with the scope of the coast-line,so it may be caused by interaction of coastal land and water.Longer-period noise （15-30 s）mainly comes from the orientation of the Pacific,Atlantic,In-dian Oceans.Furthermore,we obtain the Rayleigh wave group velocity distri-bution maps in the whole studied area for the periods from 5 s to 28 s using the ambient surface wave tomography algorithm.The tomographic results revealed that in Guangdong and its adjacent areas the crustal lateral variation is small, and the surface sediment thickness is thinner,indicating that there may be a widespread low-velocity layer in the crust.According to the characteristics of history earthquakes and surface geological structure,it can be obtained that earthquakes are mainly distributed in the vicinity of high- and low-velocity tran-sitional zone,suggesting there is a strong coupling relationship between surface wave velocity and earthquakes.From low group velocity anomaly,it is inferred that the high geothermal and hot springs widely distributed in Guangdong and its neighbor areas is mainly under the control and influence of the deep structure.

关 键 词：面波 层析成像 背景噪声互相关 广东及其邻域 

分 类 号：P315.31[天文地球—地震学]