利用双差定位法研究云南地震分布的活动构造意义

发布时间：2019-06-26 13:04

【摘要】：地震定位是测震学的基础工作之一,对于研究活动构造具有重要意义。双差地震定位法能够得到精确的震源的时空分布,是研究地震活动和活动构造之间关系的有力武器。本文利用云南数字地震台网记录的天然地震观测报告和数字波形数据,应用波形互相关技术计算波形互相关走时差数据,使用双差定位法对云南地区2009-2014年发生的M≥1.0级的地震进行重定位,得到整个云南地区的精细的地震活动图像。本文着重强调波形互相关数据的计算和使用,主要研究目的是：快速的获得稳定可靠的高精度波形互相关走时差数据；数据组合和大研究区域的分块定位,获得尽可能多的地震定位结果；分析重定位地震的时空分布和云南地区活动构造的关系,反映活动构造的细节特征。本文提出了时域多通道相关检测函数,该函数可以提高计算效率,获得稳定的互相关走时差数据。本文同时采用了一些准则对目录走时差数据和互相关走时差数据进行筛选,确保走时差数据的可靠性。由于目录数据和互相关数据各有优缺点,本文将两者进行有机组合,在确保定位精度的基础上尽可能的提高定位的地震数量。本文将研究区域分为13块,分块定位,共得到33328个地震的定位结果,采用统计学方法评估了定位误差和震源参数相关性。结果表明,互相关数据能够提高定位精度和减弱震源参数之间的相关性,是双差定位法的关键。本文分析2009～2014年云南地区地震总体的时空分布和某些地震密集地区的地震时空分布,结合前人研究,探讨了地震分布和活动构造的关系,得出了一些有意义的结论。重定位后,地震序列分布特征显现,与附近断裂和区域应力场有良好的对应。通过分析地震序列的时空分布发现,主震发生前一般会存在一段时间的地震活动平静期,表明区域应力正在积累,为大地震的发生提供能量；主震发生时,地震活动出现高峰,而后随时间有起伏的逐渐衰减；强余震也能够引发高阶余震序列,使地震活动出现小高峰。地震序列的优势分布方向与附近断裂和区域应力场有关,但是,大的地震会破坏区域应力场和附近地质结构,使得地震序列出现新的优势分布方向,因此,地震序列的分布同样受到由主震或大的余震引发的局部应力场的控制。通过对云南地区整体地震活动的震中和震源深度分布进行分析,发现不仅4级以上的中强地震沿附近活动断裂分布,14级的中小地震也多数沿活动断裂分布。川滇菱形块体内部也分布有少量的中小地震,推测川滇菱形块体在整体运动的过程中,内部受力并不均匀,导致地层出现错动,形成断裂,产生地震。川滇菱形块体内部可能存在多条隐伏断裂。震源深度的分布与活动断裂也具有明显的对应关系,深大断裂处,震源深度较深。少数小地震的震源深度已进入下地壳甚至上地幔,中强地震大多发生于上地壳,并且随着震级增大,震源平均深度越深,但是深度分布范围越窄。震源深度的分布特征与云南地壳“北深南浅”的特征相符合。本文的研究表明,地震活动的时空分布能很好的反映活动构造的特征,与活动构造之间具有密切的关系。
[Abstract]:Seismic location is one of the basic work of the seismology, and it is of great significance to study the structure of the activity. The spatial and temporal distribution of the seismic source can be obtained by the double-difference seismic location method, which is a powerful weapon for studying the relationship between the seismic activity and the activity structure. By using the natural seismic observation report and the digital waveform data recorded by the Yunnan Digital Seismic Network, the waveform cross-correlation technique is applied to calculate the time difference data of the waveform, and the two-difference location method is used to re-position the M-type 1.0-level earthquake in the region of Yunnan in 2009-2014. And the fine seismic activity images of the whole Yunnan area are obtained. In this paper, the calculation and use of waveform cross-correlation data are emphasized. The main purpose of this paper is to obtain stable and reliable high-precision waveform and to close the time-difference data with each other. The spatial and temporal distribution of the relocated earthquake and the relationship between the structure of the activities in Yunnan are analyzed, and the details of the structure of the activity are reflected. In this paper, a time-domain multi-channel correlation detection function is proposed, which can improve the calculation efficiency and obtain stable cross-correlation time difference data. At the same time, some criteria are used to screen the time difference data of the directory and the time difference data of each other, so as to ensure the reliability of the time difference data. Because of the advantages and disadvantages of the catalogue data and the cross-correlation data, this paper makes an organic combination, and improves the number of the positioning as much as possible on the basis of ensuring the positioning accuracy. In this paper, the study area is divided into 13 blocks, and the positioning results of 33328 earthquakes are obtained. The correlation between the positioning error and the source parameter is evaluated by the statistical method. The results show that the correlation between the positioning accuracy and the attenuation of the source parameters can be improved by cross-correlation data, which is the key to the double-difference location method. In this paper, the spatial and temporal distribution of the earthquake in Yunnan and the spatial and temporal distribution of the earthquakes in some areas of the earthquake are analyzed in this paper. The relationship between the distribution of the earthquake and the structure of the earthquake is discussed, and some meaningful conclusions are drawn. After the relocation, the distribution of the seismic sequence is characterized by good correspondence with the nearby fracture and the regional stress field. Through the analysis of the spatial and temporal distribution of the seismic sequence, it is found that there is a period of quiet period of the seismic activity before the main shock occurs, indicating that the regional stress is accumulating and providing the energy for the occurrence of the large earthquake; when the main shock occurs, the earthquake activity is at a peak, The strong aftershock can also cause high-order aftershock sequence to make the earthquake activity small peak. The dominant distribution direction of the seismic sequence is related to the nearby fracture and the regional stress field. However, the large earthquake will destroy the regional stress field and the nearby geological structure, so that the seismic sequence has a new dominant distribution direction, so, The distribution of the seismic sequence is also controlled by the local stress field induced by the main shock or the large aftershock. Based on the analysis of the epicenter and the depth of the focal depth of the whole seismic activity in Yunnan, it is found that not only the mid-strong earthquakes in the vicinity of level 4 are distributed in the vicinity, but the small and medium-sized earthquakes of class 14 are also distributed along the active faults. Small and medium-sized earthquakes are also distributed in the interior of the Sichuan-Yunnan diamond-shaped block, and it is assumed that the internal stress is not uniform in the process of the whole motion of the Sichuan-Yunnan diamond-shaped block, and the formation of the stratum is wrong, and the fracture is formed and the earthquake is generated. There may be a plurality of hidden faults inside the Sichuan-Yunnan diamond-shaped block. The distribution of the depth of the source and the active faults also have a clear corresponding relation, and the depth of the source is deeper than the depth of the source. The depth of the source of a small number of small earthquakes has entered the lower crust or even the upper crust, and the middle-strong earthquakes mostly occur in the upper crust, and as the magnitude increases, the average depth of the source is deeper, but the narrower the depth distribution. The distribution of the depth of the source is consistent with the characteristics of the crustal "the south of the north is shallow" in Yunnan. The research of this paper shows that the spatial and temporal distribution of the seismic activity can reflect the characteristics of the active structure well and have a close relationship with the structure of the activity.
【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】：P315.5

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