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近10年来,中国布设的宽频带地震台站大幅度增加.宽频带地震记录中含有大量的剪切波分裂信息,它在揭示中国大陆上地幔的各向异性特征起重要作用.本文对这些台站的远震SKS和(或)SKKS记录,采用最小切向能量的分析方法,确定各台站剪切波分裂的快波偏振方向和延迟时间.此外,还收集了前人在中国大陆及其周边地区的剪切波分裂研究的部分结果,形成拥有1020个剪切波分裂参数对的数据集.这些分裂参数展示了复杂的上地幔各向异性图像.统计分析表明,中国大陆存在较强的上地幔各向异性,平均的剪切波时间延迟为0.95 s,其中西部地区为1.01 s,东部地区为0.92 s.西部地区的各向异性强度略大于东部地区.在大尺度意义下,青藏高原及天山地区,其SKS波分裂和地表变形数据共同支持岩石圈变形模式,即地壳与岩石圈地幔是连贯变形的;东部地区的平均快波偏振方向近似平行于绝对板块运动方向,上地幔各向异性归因于软流圈流动.中部的鄂尔多斯至四川盆地一带为东、西部两种变形模式的过渡带,各向异性结构较为复杂,表现为“化石”各向异性和(或)双层各向异性.印度板块和欧亚板块的碰撞是中国大陆西部上地幔各向异性的主要影响因素,东部地区则与太平洋板块和菲律宾板块向欧亚板块俯冲有关.
In recent 10 years, the broadband seismic stations deployed in China have greatly increased.The broadband seismic records contain a large amount of shear wave splitting information, which plays an important role in revealing the anisotropy of mantle on the Chinese mainland.In this paper, Station, the teleseismic SKS and / or SKKS records of the station, the minimum tangential energy analysis method is used to determine the fast wave polarization direction and delay time of the shear wave splitting at each station.In addition, The results of the shear-wave splitting studies in the surrounding area form a dataset with 1020 pairs of shear-wave splitting parameters that show the complex anisotropy of the upper mantle.Statistical analysis shows that there is a strong In the upper mantle, the average shear-wave time delay is 0.95 s, which is 1.01 s in the western part and 0.92 s in the eastern part. The anisotropy strength in the western part is slightly greater than that in the eastern part.In the large-scale sense, the Tibetan Plateau And the Tianshan Mountains, the SKS wave splitting and surface deformation data jointly support the lithospheric deformation model, that is, the crust and the lithospheric mantle are coherently deformed; the average fast wave polarization direction in the eastern region is approximately flat In the direction of absolute plate motion, the anisotropy of the upper mantle is attributed to the asthenospheric flow.The transition zone from Ordos to the Sichuan Basin in the central part is the transition zone of the two deformation modes in the east and west, and the anisotropic structure is more complicated with “fossil ”Anisotropy and / or bilayer anisotropy. The collision between the Indian plate and the Eurasian plate is the main factor affecting the anisotropy of the upper mantle in the western part of China. In the eastern region, the collision with the Pacific plate and the Philippine plate to the Eurasian plate Subduction related.