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本文利用三峡库区重庆遥测台网及邻近地区台网2012年1月至12月期间的连续波形记录,通过噪声互相关,提取了这些台站间的经验格林函数.并通过获取的经验格林函数瑞利面波频散信息,反演出该区域5~40s瑞利面波相速度分布.周期5s及10s的相速度分布结果显示:四川盆地具有较厚的沉积盖层,其中盆地中部沉积层相对偏浅.而周期20s及35s的相速度分布结果显示:中下地壳的扬子克拉通整体呈现较高的相速度分布,具有相对坚硬的中下地壳结构.这其中吉首—常德的武陵山区附近出现明显高速异常,可能与江南古陆古火山岛链(雪峰—九岭弧形古火山群)活动有关,火山活动导致大量的基性-超基性幔源物质侵入地壳,造成了武陵山重力异常,并一定程度上阻挡了云贵高原和湘鄂西部的物质向南逃逸;在地形上,此处恰好对应我国地形第二阶梯向第三阶梯的过渡带,并将华南地块分隔为东西两大部分.最后我们在瑞利面波相速度成像的基础上,反演出该区域三维剪切波速度分布,结果显示四川盆地周边的龙门山、米仓山、大巴山、七曜山和大娄山等地质构造与地壳剪切波速度结构具有明显对应关系.研究结果有助于深入研究该区的深部地质构造特征与地震发生机理.
In this paper, continuous waveform records of Chongqing telemetry network in the Three Gorges reservoir area and the adjacent area network from January to December 2012 are used to extract the empirical Green’s function of these stations through noise cross-correlation, and the empirical Green’s function Rayleigh surface wave dispersion information, the phase velocity distribution of 5 ~ 40s Rayleigh wave surface in this area was inverted. The phase velocity distributions of 5s and 10s periods show that the Sichuan Basin has a thick sedimentary caprock, While the distribution of phase velocities at 20s and 35s shows that the Yangtze craton in the middle and lower crusts presents a relatively high phase velocity distribution with a relatively hard crust beneath the middle and lower crust of the Jishou-Changde area Significantly high-speed anomalies may be related to the activity of ancient volcanic island chains (Xuefeng-Jiuling arc-shaped ancient volcanic group) in the ancient southern Ganglu. The volcanic activity resulted in a large amount of basic-ultramafic mantle material that invaded the crust and caused the Wuling Mountain gravity Anomalous, and to a certain extent, blocked the Yunnan-Guizhou Plateau and western Hunan, Hubei and western materials to escape; in the terrain, where exactly corresponds to the terrain of China’s second ladder to the third ladder of the transition zone, and South China And separated into two major parts.Finally, based on the Rayleigh wave facies velocity imaging, the 3D shear wave velocity distribution in this area was inverted and the results showed that Longmen Mountain, Micangshan, Daba Mountain and Qiyao Mountain around the Sichuan Basin And Daluoshan and other geological structures and the crustal shear wave velocity structure have obvious corresponding relationship.The research results are helpful to in-depth study of the deep geological tectonics and earthquake occurrence mechanism in this area.