短周期密集台阵接收函数成像方法揭示南岭中部丹霞盆地及邻区三维地壳结构  

3D crustal structure of the Danxia Basin and its adjacent area in the central Nanling region revealed by receiver function imaging using a dense seismic array

作　　者：毕昊 方洪健 杨振 高锐 BI Hao;FANG HongJian;YANG Zhen;GAO Rui(School of Earth Science and Engineering,Sun Yat-Sen University,Zhuhai Guangdong 519082,China;Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai),Zhuhai Guangdong 519082,China)

机构地区：[1]中山大学地球科学与工程学院,广东珠海519082 [2]南方海洋科学与工程广东省实验室(珠海),广东珠海519082

出　　处：《地球物理学报》2024年第6期2322-2335,共14页Chinese Journal of Geophysics

基　　金：国家自然科学基金项目(42104046);珠江人才计划项目(2017ZT07Z066)联合资助。

摘　　要：华南陆块自早新元古代扬子与华夏地块完成拼贴以来,经历了显生宙多期陆内造山事件,其岩石圈结构与动力学演化一直是地球科学研究的热点问题.近年来,在华南地区完成的一系列地球物理探测使我们对于该地区的深部结构有了更清楚的认识.然而,目前在华南陆块开展的大多数地震学研究主要依赖于固定台及部分流动台阵数据,受限于稀疏的地震台站的分布,研究获取的地壳模型仍然存在分辨率不足的问题,这制约了我们对于区域断裂构造及深部过程的理解.本研究基于在粤北丹霞盆地及其邻区布设的短周期密集台阵,采用接收函数共转换点叠加成像方法,同时分析了不同频率的接收函数结果,获取了研究区高分辨率的地壳及盆地结构模型.研究发现该地区具有较浅的莫霍面,约28~31 km,平均地壳厚度29 km,揭示其经历了强烈的伸展减薄作用.合成数据测试结果表明复杂的三维地壳结构,如地表低速沉积层,对利用接收函数研究莫霍面起伏具有不可忽略的影响.此外,通过对比合成数据与实际观测高频接收函数中的沉积层Ps转换波及多次波震相,我们发现地表低速沉积层厚度为3 km的模型最能拟合实际观测,这一结果也得到了背景噪声成像以及相关的地质调查结果的印证.我们的研究为利用短周期密集台阵方法探测小尺度沉积盆地结构提供了一个案例.The South China Block consists of the Yangtze and the Cathaysia Block that assembled in the Neoproterozoic and underwent multiple phases of intra-continental orogeny in the Phanerozoic.Detailed tectonic evolution and the controlling factors,however,are still missing largely due to the lack of a high-resolution crustal model.Over the past few decades,many geophysical surveys have imaged the deep structure in the South China Block,but with coarse resolution because of the sparse data coverage.In this study,we derive a high-resolution crustal image in the Danxia Basin and its neighboring area in northern Guangdong Province using receiver function analysis of a short-period dense seismic array.We find that the area has a relatively shallow Moho of about 28~31 km,with an average crustal thickness of 29 km.Synthetic tests show that complex 3D crustal structure,especially those associated with the low-velocity sedimentary layers,has a non-negligible effect on the study of Moho undulations.Moreover,by fitting the synthetic data to the observed high-frequency receiver functions in the Danxia Basin,we find that a low-velocity sedimentary layer of 3 km could explain the data best.The thickness is consistent with the ambient noise tomography and other geological investigations.Our experiment shows great potential for probing small-scale sedimentary basin structures using short-period dense nodal arrays.

关 键 词：密集台阵 接收函数 地壳结构 南岭成矿带 丹霞盆地 

分 类 号：P315[天文地球—地震学]