云南地区地壳速度结构与动力学机制研究

发布时间：2018-07-25 16:10

【摘要】：本文选取了云南省境内共50个台站记录到的159个远震事件作为研究对象,涵盖经纬度范围在97。E-107。E与21。N-29。N之间。首先计算每个台站各个事件的单条P波接收函数,经挑选后的有效接收函数共2211个,接着选取简单初始模型进行二重反演获得单个事件速度结构,而后对同一个台站的多个速度结构进行bootstrap重采样统计,获得该台站下方物质分布最可能的精细速度结构。根据计算结果统计Moho面埋深情况、低速区存在位置与地下物质S波的整体分布规律并绘制相应图表。综合各个台站结果进行区域性分析讨论,从而了解研究区范围内物质分布规律与地质构造间活动情况,并推测云南省的地壳分布结构、川滇地区板块内部以及板块之间活动的动力学机制。研究结果主要有： 1、通过理论数值模拟实验与实测数据计算,论证了用bootstrap方法统计各事件结果最终获得台站下方精细速度结构是可行的,它比起叠加接收函数再进行反演要更加可靠。同时通过选取2次模型反演不同高斯参数下的接收函数,能够降低结果对初始模型的依赖。 2、研究区内地壳厚度在北偏西向逐渐增加,横向变化幅度可达30-40km,高原存在抬升隆起现象。在滇中块体附近等值线存在3个明显的舌状突出,Moho面埋深的变化幅度在各个方向上不均匀：其他区域内等值线呈均匀的递增趋势。 3、研究区地下2km深度范围内广泛分布着沉积层,之后S波速度跃变到3.0km/s以上。部分台站下方存在低速结构,这些台站多分布在深大断裂附近,火山活动区以及滇中块体内部。而在其他岩石圈较为稳固的地区如四川盆地边缘、保山块体与兰坪—思茅块体附近基本没有低速结构存在。 4、根据计算结果,本文的结论支持青藏高原下地壳物质流的运动模式。即：青藏高原下地壳物质被挤出后受到四川盆地与喜马拉雅构造结的限制,主要沿着深大断裂流入云南境内,并且物质流突破了丽江断裂,侵入到滇中块体并在块体内部集中分布。
[Abstract]:In this paper, 159 teleseismic events recorded by 50 stations in Yunnan Province are selected as research objects, covering the range of longitude and latitude between 97.E-107.E and 21.N-29.N. First of all, the single P-wave reception function of each station is calculated, and the selected effective reception function is 221, and then the single event velocity structure is obtained by double inversion with a simple initial model. Then the bootstrap resampling statistics of multiple velocity structures of the same station are carried out to obtain the most probable fine velocity structure of the material distribution under the station. According to the statistical results of the Moho surface buried depth, the location of the low velocity region and the overall distribution of the S wave of underground matter are calculated and the corresponding charts are drawn. Based on the regional analysis and discussion of the results of each station, the distribution law of matter and the activities between geological structures in the study area are understood, and the crustal distribution structure of Yunnan Province is inferred. The dynamic mechanism of intraplate and inter-plate activity in Sichuan-Yunnan area. The main results are as follows: 1. Through the theoretical numerical simulation experiment and the calculation of the measured data, it is proved that it is feasible to obtain the fine velocity structure under the station by using the bootstrap method to calculate the results of each event. It is more reliable than superposition receiving function to perform inversion. At the same time, by selecting two models to invert the reception function under different Gao Si parameters, the dependence of the results on the initial model can be reduced. The crustal thickness in the study area increases gradually in the north-west direction. The range of lateral variation can reach 30-40 km, and the uplift phenomenon exists in the plateau. There are three obvious tongue protruding surface buried depth in the central Yunnan block. The variation range of the buried depth of Moho surface is not uniform in all directions: in other regions, the isoline is increasing uniformly. 3. The underground 2km depth in the study area The sediment is widely distributed in the area, Then the velocity of S wave jumps above 3.0km/s. Some of the stations have low velocity structures, which are located near the deep fault, volcanic active area and the central Yunnan block. However, in other areas where the lithosphere is relatively stable, such as the margin of the Sichuan Basin, there is basically no low-velocity structure near the Baoshan block and the Lanping-Simao block. The conclusion of this paper supports the movement model of the lower crust material flow in the Qinghai-Xizang Plateau. That is, the material in the lower crust of the Qinghai-Xizang Plateau was restricted by the tectonic junction between Sichuan Basin and the Himalayas and flowed into Yunnan mainly along the deep and large faults, and the material flow broke through the Lijiang fault. Intruded into the central Yunnan block and distributed within the block.
【学位授予单位】：云南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P315.2

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