面波非大圆路径传播研究进展
Research progress on off-great-circle propagation of surface waves
范芮芮 1张泽铭 1叶庆东 2陈浩朋1
作者信息
- 1. 广东工业大学土木与交通工程学院测绘工程系,广州 510006
- 2. 中国地震局第一监测中心,天津 300180
- 折叠
摘要
传统面波层析成像多基于射线理论,并假定面波沿大圆路径传播.由于地球介质的横向非均匀性,面波有时会偏离大圆路径传播,引起面波入射方位角异常和多路径传播效应.本文通过总结面波非大圆路径传播的研究成果,分析了面波非大圆路径传播的主要特点及成因:面波非大圆路径传播效应随着周期的减小而增强,在短周期的非大圆路径传播效应非常明显,地壳上地幔结构的横向非均匀性是导致面波偏离大圆路径传播的主要因素.接着,介绍了测量面波入射方位角异常的两类方法——单台三分量偏振分析和台阵分析方法,其中台阵分析方法相对于单台三分量偏振分析更为可靠和稳定.讨论了面波非大圆路径传播对于面波频散测量和面波层析成像的影响.由于面波的非大圆路径传播,采用天然地震双台法测量的面波频散会高于真实值,而利用背景噪声测量的双台频散会低于真实值.因此,基于大圆路径假设的面波层析成像结果会与真实值出现偏差,特别是各向异性快波方向可能受到的影响更大.最后,本文对面波非大圆路径传播的研究方向进行了展望:在天然地震面波层析成像中,可以利用面波入射方位角异常改正双台面波相速度测量,然后再进行面波层析成像;利用谱元法模拟地震波是研究面波非大圆路径传播的一种有效手段,既需要考虑全球大尺度地壳上地幔结构,也需要考虑研究区内部精细三维结构对于面波非大圆传播的影响.
Abstract
The traditional surface wave tomography is usually based on ray theory and assumes that surface waves propagate along great-circle paths.Due to the lateral heterogeneity of the Earth's medium,surface waves may deviate from the great-circle path,causing arrival angle anomalies of surface waves and multi-path propagation effects.This paper summarizes the research results on the off-great-circle propagation of surface waves,analyzes the main characteristics and causes of off-great-circle propagation of surface waves:the off-great-circle propagation effect of surface waves increases with decreasing period,being particularly pronounced in short periods,and the lateral heterogeneity of the crust-mantle structure is the main factor leading to the deviation of surface waves from great-circle propagation.Then,two types of methods for measuring the arrival angle anomaly of surface waves are introduced:single-station three-component polarization analysis method and array analysis method,with the array analysis method being more reliable and stable compared to single-station three-component polarization analysis.Due to the off-great-circle propagation of surface waves,the surface wave dispersion measured by traditional two-station method will be higher than the true value,while the two station ambient noise dispersion will be lower than the true value.Therefore,the surface wave tomography results based on the great-circle assumption will deviate from the real values.In particular,the anisotropic fast direction of surface waves may be more affected.The paper discusses the impact of off-great-circle propagation of surface waves on surface wave dispersion measurements and surface wave tomography,and emphasizes the necessity of considering the off-great-circle propagation effect of surface waves in high-precision surface wave tomography studies.Finally,the paper looks ahead to future research directions in off-great-circle propagation of surface waves:in event-based surface wave tomography study,the arrival angle anomaly of surface waves can be used to correct the measurement of phase velocity for seismic station pairs,followed by surface wave tomography;using the spectral element method to simulate seismic waves is an effective means to study the off-great-circle propagation of surface waves,which requires considering influence of both the global-scale crust-mantle structure and the fine three-dimensional structures within the study area on the non-great-circle propagation of surface waves.
关键词
面波层析成像/非大圆路径传播/聚束分析/入射方位角异常/多路径效应Key words
Surface wave tomography/Off-great-circle propagation/Beamforming/Arrival angle anomaly/Multi-path effects引用本文复制引用
基金项目
国家自然科学基金(41804061)
广州市基础研究计划基础与应用基础研究专题(2023A04J1526)
出版年
2024
NETL
NSTL
万方数据