短周期线性密集台阵揭示宣城地区浅部地壳速度结构及断裂发育特征  

Short-period linear array reveals velocity structure and fault development characteristics of the shallow crust in the Xuancheng area

作　　者：方捷 姚华建[1,2] 李杰 李俊伦[1,2] 周桂理 Fang Jie;Yao Huajian;Li Jie;Li Junlun;Zhou Guili(School of Earth and Space Sciences,University of Science and Technology of China,Hefei 230026,China;Mengcheng National Geophysical Observatory,Mengcheng 233500,China;Anhui Earthquake Agency,Hefei 23003l,China)

机构地区：[1]中国科学技术大学地球和空间科学学院,合肥230026 [2]蒙城地球物理国家野外科学观测研究站,蒙城233500 [3]安徽省地震局,合肥230031

出　　处：《地球与行星物理论评（中英文）》2025年第2期201-214,共14页Reviews of Geophysics and Planetary Physics

基　　金：国家重点研发计划资助项目(2021YFC3000704);国家杰出青年科学基金资助项目(42125401)。

摘　　要：宣城市位于东南丘陵与长江中下游平原过渡地带,区内经历多期构造活动,地质构造复杂且断裂十分发育,开展宣城地区浅部速度结构和断裂带探测,不仅有助于深入了解区内地质构造和成矿作用,还可以为区域地震危险性和危害性评价提供重要的参考模型.本文在研究区布设了一条由110套三分量地震仪组成的短周期线性密集台阵,利用采集的一个月的三分量背景噪声数据,采用噪声谱比方法(HVSR)探测研究区场地峰值频率及基岩界面结构;通过垂直分量背景噪声数据重建经验格林函数,采用拓距相移法(ERPS)提取相速度频散曲线并反演线性台阵下方浅部地壳精细横波速度结构.基于HVSR计算的场地峰值频率和基岩界面埋深,刻画了测线下方浅部地表松散沉积层的结构,结果显示研究区内皖南山区基岩埋深较浅,盆地区域基岩埋深较深,地表松散沉积层的厚度最大可至地下80 m,此外还评估了区内地震破坏性和建筑的抗震性,认为研究区内平均振幅放大系数相对较高,局部区域可能会产生明显的地震放大效应,并且皖南山区低矮建筑(1~2层)及宣城—南陵盆地区域的高层建筑(7层及以上)在抗震设防上应当特别注意;依据反演的二维横波速度模型,获得了研究区浅部地壳6 km以深的结构,结果显示宣城—南陵盆地在浅部表现为明显的低速特征,其基底深度可达2 km,并且盆地部分区域呈现相对高速的异常特征,指示在区域多期构造活动中产生的岩浆侵入和逆冲推覆构造作用。此外,区内深部总体表现为高低速异常交替分布的“叠瓦状”构造模式,出现的多处低速异常带推断分别是周王断裂、江南断裂和茅山断裂以及清水河—河湾断裂的构造破碎带,指示了研究区内经历的多期次挤压—拉伸的强烈变形改造.综合上述研究成果,本研究为宣城地区地质构造条件的分析、地震危险性及危�Xuancheng City is situated in the transitional zone between the southeastern hills and the middle and lower reaches of the Yangtze River plain.This region has undergone multiple stages of tectonic activity,resulting in complex geological structures and well-developed fault systems.Investigating the shallow velocity structure and fault zones in the Xuancheng area not only enhances our understanding of the region's geological structure and mineralization but also provides an important reference model for assessing regional seismic risks and hazards.A short-period linear array consisting of 110 three-component seismometers was deployed in the study area.Using one month of collected three-component ambient noise data,the horizontal-to-vertical spectral ratio(HVSR)method was applied to detect site peak frequency and the bedrock interface structure.The empirical Green's functions were reconstructed from the vertical ambient noise data,and the phase velocity dispersion curve was extracted using the extended range phase shift(ERPS)method.Based on the site peak frequency and bedrock interface burial depth derived from HVSR,the structure of the shallow,loose sedimentary layers along the survey line was delineated.The results indicate that bedrock depth in the southern Anhui mountainous region is relatively shallow,whereas it is deeper in the basin areas.The thickness of the loose surface sedimentary layer can reach up to 80 m below ground.Furthermore,a seismic damage assessment and earthquake resistance evaluation of buildings in the area revealed that the average amplification factor of ground motion is relatively high.Localized areas may experience significant seismic amplification effects,warranting special attention to the earthquake resistance of low-rise buildings(1-2 stories)in the southern Anhui mountainous region and high-rise buildings(7 stories or more)in the Xuancheng-Nanling basin.According to the inverted 2D shear wave velocity model,the structure of the shallow crust down to a depth of 6 km in the study area

关 键 词：背景噪声成像 H/V谱比 拓距相移 地壳浅层结构 断裂带探测 地震灾害预防 

分 类 号：P315[天文地球—地震学]