华南地块及邻区基于背景噪声的壳幔三维S波速度结构  

THREE-DIMENSIONAL S-WAVE VELOCITY DISTRIBUTION BASED ON AMBIENT NOISE ANALYSIS IN SOUTH CHINA BLOCK AND ITS ADJACENT AREAS

作　　者：宫猛 吕坚 郑勇[4] 谢祖军 盛书中 张杏棉 GONG Meng;LÜJian;ZHENG Yong;XIE Zu-jun;SHENG Shu-zhong;ZHANG Xing-mian(Engineering Research Center for Seismic Disaster Prevention and Engineering Geological Disaster Detection of Jiangxi Province,Nanchang 330013,China;State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences,Beijing 100083,China;East China University of Technology,School of Geophysics and Measurement-Control Technology,Nanchang 330013,China;China University of Geosciences,Wuhan 430074,China)

机构地区：[1]江西省防震减灾与工程地质灾害探测工程研究中心,南昌330013 [2]地质过程与矿产资源国家重点实验室(中国地质大学),北京100083 [3]东华理工大学,地球物理与测控技术学院,南昌330013 [4]中国地质大学,武汉430074

出　　处：《地震地质》2022年第4期1011-1028,共18页Seismology and Geology

基　　金：中国地震局地震科技星火计划项目(XH20032);江西省自然科学基金(20202BABL203035);地质过程与矿产资源国家重点实验室开放课题(GPMR202114);江西省防震减灾与工程地质灾害探测工程研究中心开放基金(SDGD202010)共同资助。

摘　　要：文中使用华南地块及其邻区609个宽频地震仪记录的2010年1月—2012年12月共36个月垂直分量(Z分量)的连续噪声数据,通过波形互相关和叠加计算得到各台站对间的经验格林函数,采用时频分析方法(FTAN)提取台站对之间的瑞利波相速度频散曲线,并使用非线性贝叶斯蒙特卡罗方法反演获得华南地块及其邻区的三维S波速度结构。结果显示,S波速度的分布特征与地表地质和构造特征表现出较好的相关性,能清晰地揭示出地壳内部的横向速度变化。盆地和地堑地区由于受沉积层的影响,浅层的S波速度表现为低速异常。江汉盆地和四川盆地的中下地壳存在高速异常,表明盆地的中、下地壳较冷、硬。四川盆地内部由于存在上地幔上拱现象,其壳—幔S波速度整体相对较高,且盆地内部中心区域的S波速度高于边缘区域。位于华南地块内部的扬子地块和华夏地块由于演化过程有所不同,上地幔的S波速度结构存在较大差异。扬子地块的S波速度相对较高,说明其块体内部结构相对稳定,而华夏地块的S波呈现低速异常,预示着在其演化过程中存在强烈的岩浆活动。位于华南地块西南边界以西区域的壳—幔S波速度呈低速异常,可能预示着青藏高原东缘中下地壳存在软流层。秦岭-大别造山带东、西2段的S波速度结构存在较大差异,以地壳厚度过渡带为界呈现东高西低的分布特征。鄂尔多斯块体的壳—幔S波速度相对较高,说明其块体内部结构相对稳定,但其西南角上地幔中的S波呈现低速异常,可能表明华北克拉通上地幔热流已经开始对鄂尔多斯的岩石圈进行“侵入”改造。The South China block,located in the east of the Eurasian plate,mainly consists of the Yangtze block and the Cathaysia block.The South China block is bounded by the eastern margin of the Qinghai-Tibet Plateau in the west,the Qinling-Dabie orogenic belt in the north,and its eastern boundary extends from the southeast coast to the north,through the Taiwan Strait,and then along the Ryukyu Island arc to the west direction.The neotectonic movement of the South China block is intense.It is not only the continental margin with the most active crustal growth and continental accretion,but also the tectonic belt with the most intense core-mantle mass transfer and the coupling zone of the inner layers of the Earth.Therefore,the crust-mantle velocity structure of the South China block and its formation and evolution have always been a hot topic in earth science research.In this paper,we collected continuous vertical component broadband seismic data between January 1,2010 and December 31,2012 from the regional networks of 609 stations and used ambient noise tomography method to inverse the three-dimensional S-wave velocity structure of South China block and its adjacent area.Firstly,the seismograms are cut into daily segments and decimated at a sampling rate of 1 Hz.After the removal of the mean,trend,and instrument response,a 3~150 s band-pass filter is applied.In order to reduce the effect of earthquakes and instrumental irregularities on cross-correlations,we normalized the seismograms with a time-frequency normalization method.Then,we computed daily cross-correlations for each station pairs and stacked all of them by using normalized linear stacking method to obtain cross-correlation functions.Next,the phase velocity dispersion curves of Rayleigh surface wave were extracted by frequency-time analysis method.Finally,the three-dimensional S-wave velocity structure of the study area was obtained by using nonlinear Bayesian Monte Carlo inversion method.The results show that the S-wave velocity distribution has a good correlat

关 键 词：背景噪声 相速度 频散曲线 S波速度 壳—幔速度结构 

分 类 号：P315.2[天文地球—地震学]