华北和云南地区地壳上地幔S波速度与方位各向异性结构研究

发布时间：2018-06-28 08:27

本文选题：华北 + 云南　；参考：《武汉大学》2015年博士论文

【摘要】：本文提出了通过双台互相关-多地震叠加法提取双台间的面波频散,提高频散测量的精度。利用华北地震流动台阵和云南数字地震台网记录的天然地震数据,提取10-60s的Rayeligh波相速度频散。利用基于单函数的Tarantola方法进行Rayleigh波相速度各向同性层析成像,得到不同周期的相速度分布,并进一步反演得到华北和云南地区地壳上地幔S波速度结构；利用基于多函数的Tarantola方法进行相速度各向异性层析成像,得到不同周期的相速度方位各向异性分布,并进一步反演得到华北和云南地区的地壳上地幔S波方位各向异性结构。结合前人研究,探讨了两个地区的地球动力学问题,并得出了一些非常有价值的结论。在华北地区,南北重力带两侧的S波速度结构存在明显不同,南北重力带的形成和东部块体的破坏可能与太平洋俯冲有关。大同附近存在明显的的低速带(50-110km),可能与来自西部块体下方地幔转换带处的软流圈上涌有关。张蓬断裂带的东南部存在一个低速带,低速带内方位各向异性方向平行于低速带走向,张蓬断裂带可能切断了岩石圈,提供了软流圈上涌通道。华北克拉通的东部块体的破坏可能既与太平洋板块上的软流圈上涌有关,也与来自西部块体下方的软流圈上涌有关。京津唐地区存在一个明显的低速带(30-50 km),这个低速带可能与发生在该地区的大地震有关,促进的地震发生。华北地区的历史大地震大多发生在中上地壳的S波高低速交界的地方,速度的转换可能有利于大地震的发生。研究区的S波方位各向异性在横向和垂向都发生明显的变化。在中部造山带存在非常明显的分层各向异性,在浅部与造山带走向一致,而在深部则垂直于造山带走向。中部造山带的分层各向异性结构可能是该地区不同SKS观测结果存在差异的原因。云南地区的研究热点问题是中下地壳低速流与壳幔耦合机制。本文的研究结果表明云南地区的中下地壳低速层是确实存在的,低速层是连通的,没有被断层分割和围限,低速层的方位各向异性快波方向平行于低速层的走向,支持云南地区存在中下地壳低速流的观点。云南地区的壳幔耦合机制比较复杂,不同地区具有不同的耦合特征。在绿汁江断裂东侧的滇中地块和扬子克拉通,在20-110km有着比较稳定的近N-S向S波快轴方向,壳幔是耦合的。在绿汁江断裂西侧的滇中地块部分,存在很明显的分层各向异性,这一部分地块是壳幔解耦的。西南部的保山地块在浅部和深部的S波速度和方位各向异性特征存在明显不同,该地区的壳幔是解耦的。S波速度结构图显示滇中地块与扬子克拉通在深部具有更加一致的结构,在80-110km主要呈现高速特征,滇中地块在整体上仍然隶属于扬子克拉通。腾冲地块、保山地块和思茅地块在80-110km呈现明显的低速特征,可能对应于深部的软流圈上涌。在20-60km,保山地块南部存在一个非常明显的高速异常,且高速异常的形态与澜沧江断裂形态基本一致。在地质历史时期,可能存在保山地块向东北向挤压思茅地块的构造活动,形成了现今澜沧江断裂的形态。云南地区大多数地震都沿着大断层分布,其中主要发生在中部的滇中地块及西部的怒江断裂、澜沧江断裂附近。大多数地震都发生在中上地壳S波低速或者高低速交界的地方,高速异常区域几乎没有大地震发生。红河断裂和哀牢山断裂附近的大地震比较少,可能是由于思茅地块与滇中块体的速度结构更为接近,两者相对稳定。
[Abstract]:In this paper, a two platform cross correlation multi seismic superposition method is proposed to extract the frequency dispersion of surface wave between two platforms and improve the accuracy of dispersion measurement. Using the natural seismic data recorded by the North China seismic array and the Yunnan digital seismic network, the Rayeligh wave velocity dispersion of 10-60s is extracted. The Rayleigh wave based on the single function Tarantola method is used. Phase velocity isotropic tomography is used to obtain the phase velocity distribution of different periods and further inversion of the S wave velocity structure in the crust and upper mantle in North China and Yunnan, and the phase velocity anisotropic tomography based on the Tarantola method based on multi function is used to obtain the azimuthal anisotropy of the phase velocity in different periods, and further inverse. The S wave azimuthal anisotropy structure of the crust and upper mantle in North China and Yunnan is derived. Based on previous studies, the geodynamic problems of the two regions are discussed and some very valuable conclusions are drawn. In North China, the S wave velocity structure on both sides of the north and South gravity zones is distinct, the formation of the north and the South gravity zones and the eastern block. The damage may be related to the Pacific subduction. There is a clear low velocity zone near Datong (50-110km), which may be related to the upwelling of the asthenosphere from the mantle transition zone below the western block. There is a low velocity zone in the southeast of the Chang Peng fault zone. The direction of the azimuthal anisotropy in the low velocity zone is parallel to the low velocity zone, and the Chang Peng fault zone may be possible. The disruption of the lithosphere provides a surge channel in the asthenosphere. The destruction of the eastern block of the North China Craton may be related to both the upwelling of the Pacific rim and the upwelling of the asthenosphere below the western block. There is a clear low velocity zone (30-50 km) in the Beijing Tianjin Tangshan region, which may occur in the region. The large earthquakes in the region of North China mostly occur at the junction of S wave high and low velocity in the middle and upper crust, and the conversion of velocity may be beneficial to the occurrence of large earthquakes. The azimuthal anisotropy of the S wave in the study area changes obviously in the transverse and vertical directions. There are very obvious points in the middle orogenic belt in the central region. The stratified anisotropy is consistent with the orogenic belt in the shallow part, while in the deep part it is perpendicular to the orogenic belt. The stratified anisotropic structure of the Central Orogenic belt may be the reason for the difference of the SKS observation results in the region. The hot issue in Yunnan area is the low velocity flow and the crust mantle coupling mechanism in the middle and lower crust. The results of this paper show the results of this paper. The low-speed layer of the middle and lower crust in the Yunnan region is true. The low velocity layer is connected, and the low velocity layer is not divided and bounded. The direction of the azimuthal anisotropic fast wave in the low velocity layer is parallel to the low velocity layer, supporting the low velocity flow in the middle and lower crust in the region of Yunnan. The crust and mantle coupling mechanism in the Yunnan region is complex and the different regions are in different areas. Different coupling characteristics. The central Yunnan massif and Yangzi craton on the east side of the green Jujiang fault have a relatively stable near N-S to S wave fast axis direction, and the crust and mantle are coupled. There is a distinct stratified anisotropy in the middle part of the Middle Yunnan block on the west side of the green juice River fault. This part of the block is the crust mantle decoupling. The Baoshan land in the southwest of Baoshan. There are obvious differences between the S wave velocity and azimuthal anisotropy in the shallow and deep parts. The crust and mantle in this area is a decoupled.S wave velocity structure map showing that the central Yunnan massif and the Yangtze craton have a more consistent structure in the depth, and in the 80-110km, the high speed characteristics are mainly present, and the central Yunnan block still belongs to the Yangtze craton on the whole. The flush block, Baoshan block and Simao massif show obvious low velocity characteristics in 80-110km, which may correspond to the upwelling of the deep soft flow circle. In the south of the Baoshan block, there is a very obvious high velocity anomaly in the south of the Baoshan block, and the shape of the high-speed anomaly is basically the same as that of the Lancang River fault. In the geological historical period, there may be the Baoshan massif eastward. The tectonic activity of the northward extrusion of Simao massif forms the form of the present fault of the present Lancang Cangjiang fault. Most of the earthquakes in the Yunnan region are distributed along the large faults, mainly occurring in the central Yunnan block and the Nu River fault in the West and near the Lancang River fault. Most of the earthquakes occur at the low or high low speed boundary of the middle and upper crust S waves. There are few large earthquakes in the high velocity anomaly area. The large earthquakes near the Honghe fault and Ailao Mountain fault are relatively small, which may be due to the closer speed structure of the Simao block and the central Yunnan block, and the two are relatively stable.
【学位授予单位】：武汉大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：P315

【相似文献】