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和其它地震成像方法比较,背景噪声成像方法能够较有效的获得地壳以及上地幔的速度结构.本研究将PhaseWeighted-Stack方法应用到了互相关函数的叠加过程中,有效的增强了Love波信号,压制了获得的格林函数中的噪声.本文将这种技术应用到了北京大学与中国地质科学院合作布设在秦岭及其周边地区的(69台)宽频带流动地震台阵,利用台站的水平分量噪声记录提取的Love波频散曲线来获得台站间Love波相、群速度,进而得到了从6 s到30 s周期的Love波相速度二维分布图像.进一步进行了三维SH波速度反演,获得了研究区地壳和上地幔SH波3D速度结构,为研究该地区构造运动和上地幔动力学提供基础观测资料.一个重要的结果显示秦岭造山带以及鄂尔多斯块体外部西北方向在50 km深度呈现较强的SH波低速异常,这个连贯的低速异常带是否对应于青藏高原上地幔物质在鄂尔多斯块体和四川盆地块体之间的向东扩展流动而形成的温度异常或者部分熔融体还有待于进一步验证.
Compared with other seismic imaging methods, the background noise imaging method can obtain the velocity structure of the crust and the upper mantle more effectively.In this study, the PhaseWeighted-Stack method was applied to the superposition of the cross-correlation function, effectively enhancing the Love wave signal, suppressing We get the noise of Green’s function obtained.This paper applies this technique to the (69) broadband mobile seismic array co-located by Peking University and the Chinese Academy of Geological Sciences in the Qinling Mountains and its surrounding areas. Using the station’s horizontal component noise record The Love wave dispersion curve was extracted to obtain the Love wave phase and group velocity between stations, and then the two-dimensional distribution of Love wave phase velocity from 6 s to 30 s was obtained. The 3D SH wave velocity inversion was further obtained, The velocity structure of SH wave in the crust and upper mantle in the study area provides the basic observation data for the study of tectonic movement and upper mantle dynamics in this area.An important result shows that the Qinling orogenic belt and the northwestern direction of the Ordos block have a higher velocity Strong SH wave low-velocity anomalies, whether this coherent low-velocity anomaly corresponds to the Tibetan Plateau upper mantle material in the Ordos block Or partial melting temperature anomaly between east and Sichuan block body formed extended flow needs to be further verified.