利用面波直接反演方法研究滇西北地壳三维S波速度结构  

Three-dimensional S-wave velocity structure of the crust in Northwest Yunnan using the surface wave direct inversion method

作　　者：茶文剑 王伟君[3] 张圆缘 黑贺堂 CHA Wenjian;WANG Weijun;ZHANG Yuanyuan;HEI Hetang(Dali Center,China Seismic Experimental Site,Yunnan Earthquake Agency,Dali 671000,Yunnan,China;Northwestern Yunnan Crustal Tectonics Observatory of CEA,Dali 671000,Yunnan,China;Institute of Earthquake Forecasting,CEA,Beijing 100036,China;Kaiyuan Earthquake Agency,Honghe 661600,Yunnan,China)

机构地区：[1]云南省地震局中国地震科学实验场大理中心,云南大理671000 [2]云南大理滇西北地壳构造活动中国地震局野外科学观测研究站,云南大理671000 [3]中国地震局地震预测研究所,北京100036 [4]开远市地震局,云南红河661600

出　　处：《地震工程学报》2025年第2期458-467,共10页China Earthquake Engineering Journal

基　　金：中国地震局地震预测研究所基本科研业务专项(CEAIEF20220402);云南省地震局科技人员传帮带项目(CQ3-2021004);中国地震局地球物理研究所基本科研业务费专项(DQJB23Z03-02);云南省地震科技创新团队(CXTD202411)。

摘　　要：我国滇西北地区(25°~27°N,99°~101°E)是川滇菱形地块西边界所在区域,由于构造运动活跃,是我国地震灾害比较严重的地区,非常有必要深入研究其孕震结构。文章利用该地区69个短周期流动台站2020年记录的连续波形,通过背景噪声互相关计算和时频分析方法,提取所有台站对Rayleigh面波相速度频散曲线,采用基于射线追踪的面波频散直接反演方法,得到研究区地下三维S波速度结构。研究结果表明,研究区域上地壳速度结构存在明显差异,特别是大型断裂带的分段特征明显。如维西—乔后断裂带浅层5 km内整体表现为西北部高速,东南部低速;程海断裂带北段高南段低,在宾川盆地存在厚度约5 km的低速异常,说明宾川盆地存在较厚的沉积层。地壳浅层波速和地形起伏有较好的对应关系,在盆地区域整体表现为低速,高山区域为高速。2021年漾濞M S6.4地震发生在S波高低速过渡区域,研究区中下地壳内存在不同程度的低速区,可能为地震的发生提供了孕震环境。The northwestern region of Yunnan Province(25°—27°N,99°—101°E)lies along the western boundary of the Sichuan—Yunnan rhomboid block,a zone marked by active tectonic movements.This region is among the most seismically hazardous in China,requiring a comprehensive understanding of its seismogenic structures.In 2020,we analyzed continuous waveforms from 69 short-period stations in the area.We extracted Rayleigh surface-wave phase-velocity dispersion curves using cross-correlation of ambient noise and time-frequency analysis.We derived the Dl S-wave velocity structure beneath the study area using the direct inversion method of surface-wave dispersion based on ray tracing.The results reveal significant variations in the crustal velocity structure,particularly in segmented features along major fault zones.For example,at a depth of 5 km beneath the Weixi—Qiaohou fault zone,high velocities are observed in the northwestern section,whereas low velocities dominate the southeastern section.Similarly,the Chenghai fault zone exhibits high velocities in its northern segment and low velocities in the southern segment.In the Binchuan Basin,a low-velocity anomaly of approximately 5 km suggests the presence of a substantial sedimentary layer.Shallow crustal wave velocity correlates closely with terrain relief,with low velocities observed in basin areas and high velocities in mountainous regions.The 2021 Yangbi M 6.4 earthquake occurred in a transition zone between high and low S-wave velocities.In addition,low-velocity zones of varying extents are identified in the middle and lower crust,potentially providing a seismogenic environment for the earthquake.

关 键 词：滇西北地区 背景噪声 面波直接反演方法 地壳S波速度结构 孕震环境 

分 类 号：P315.2[天文地球—地震学]