ISSN 1004-4140
    CN 11-3017/P

    基于同步和异步环境背景噪声成像研究广州地下三维速度结构

    Three-dimensional Velocity Structure Beneath Guangzhou, China, Derived from Synchronous and Asynchronous Ambient Noise Tomography

    • 摘要: 广州地处多活动断裂交汇的珠江三角洲北缘,其地下结构复杂,地质灾害风险高。为获得高分辨率的地壳剪切波速度结构,本文结合两期临时地震台网与地方永久台站数据,联合同步(C1)与异步(C2)环境噪声互相关方法进行层析成像。C1方法提取局部台站间射线路径,C2方法构建跨子阵远距离射线路径,在1~8s周期范围内显著提高了路径覆盖与交叉密度。通过多重滤波分析提取频散曲线,我们采用基于小波稀疏约束的直接反演算法,构建了0~7km深度内的三维S波速度模型。结果表明,广州—从化断裂(GCF)、瘦狗岭断裂(SF)、广州—三水断裂(SSF)、珠江口断裂(ZJF)等主要断裂与低速异常具有良好的空间对应性,反映出断裂控制下的沉积盆地结构;同时,GCF深部低速异常揭示出其存在构造反转过程。本研究表明,融合C1与C2的环境噪声成像技术可有效提升城市区域地壳结构成像质量,其结果为广州地区地质灾害防控与资源探测提供了关键地球物理依据。

       

      Abstract: Located at the northern margin of the Pearl River Delta, Guangzhou is characterized by complex subsurface structures resulting from the intersection of multiple active faults, leading to elevated geohazard risks. This study derives a high-resolution crustal shear-wave velocity structure by integrating data from two temporary seismic networks and local permanent stations using a joint ambient noise tomography approach that combines synchronous (C1) and asynchronous (C2) cross-correlation techniques. The C1 method extracts short-range ray paths between local stations, whereas the C2 method constructs long-range paths across sub-arrays, significantly improving both path coverage and crossing density within the 1–8 s period band. Using multiple-filter analysis to extract Rayleigh wave dispersion curves, we employ a wavelet-based, sparsity-constrained direct inversion algorithm to construct a three-dimensional shear-wave velocity model down to 7 km depth. The results reveal pronounced spatial correlations between major faults—including the Guangzhou-Conghua (GCF), Shougouling (SF), Guangzhou-Sanshui (SSF), and Zhujiangkou (ZJF) faults—and distinct low-velocity anomalies, that reflect sedimentary basin structures controlled by fault activity. Furthermore, a prominent deep low-velocity anomaly beneath the GCF suggests an ongoing or past tectonic inversion process. This study demonstrates that the combined application of C1 and C2 ambient-noise tomography significantly enhances the imaging resolution of crustal structures in urban environments, providing crucial geophysical constraints for geohazard assessment and resource exploration in the Guangzhou region.

       

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