地震精定位新方法及芦山地震相关研究

发布时间：2018-05-24 06:28

本文选题：地震重定位 + 地震干涉　；参考：《中国科学技术大学》2016年博士论文

【摘要】：本论文分为三个部分：(1)我们首先介绍一种高分辨率的地震精确定位新方法(命名为hypoRelocate)以及这个方法在芦山地震余震重定位中的应用；(2)然后讨论芦山地震前震检测的研究工作：(3)最后展示芦山地震余震中的重复地震的研究工作,并试图解释余震(第一部分中精确重定位的余震以及较大的重复震群)分布与有限断层反演的破裂滑动分布模型的关系。我们发展了一套地震精定位新方法,这个方法在地震定位中除了用到传统的地震波绝对走时和地震间的相对走时差,还加入了一种新约束一一震源间叠加的地震尾波互相关走时信息。这个新方法通过模拟退火法寻找以上三种约束的总残差最小值来实现地震最佳位置和发震时刻的反演。这种方法在地震间走时差精确约束地震相对位置的基础上,通过构建地震震源间叠加的地震尾波互相关波形走时,更加精确地约束震源间的距离；通过地震波绝对走时的加入削弱地震定位结果对初始地震目录位置的依赖。我们将这种新方法应用于芦山地震和余震的重定位中,并与流行的地震相对定位精定位程序hypoDD进行对比。结果显示叠加的地震尾波互相关走时的约束和地震波绝对走时的加入,能够更加精确地约束地震的相对位置和绝对位置。我们利用最新的微小地震信号检测方法一匹配定位法(match and locate method)对芦山地震进行了前震检测。通过对震前六个月时间连续波形的扫描,我们没有发现地震目录以外的小地震信号。尽管在芦山地震发生前,震中附近区域也有一些小的地震事件出现,但是主震发生前该区域的地震活动没有明显增加的趋势。通过对芦山地震余震的波形对比,我们发现在余震中存在一定数量波形相似度较高的重复地震,这些重复地震一般震级较小并且沿断层的各个区域都有分布。较大的重复地震群与高精度重定位后的较大余震的分布和有限断层反演的破裂滑动模型的对比分析显示余震大多分布在断层主要破裂周围滑动量较小的区域,同时主断层的破裂可能触发周围区域其它断层的地震活动。
[Abstract]:This paper is divided into three parts: 1) We first introduce a new high-resolution accurate seismic location method (named hypoRelocateand its application in Lushan aftershock relocation) and then discuss the Lushan earthquake foreshock detection. At the end of the study on repeated earthquakes in the aftershocks of the Lushan earthquake, This paper also attempts to explain the relationship between the distribution of aftershocks (accurately relocated aftershocks in the first part and large repeated earthquake swarms) and the fracture slip distribution model of finite fault inversion. We have developed a new method of accurate seismic location, which uses not only the traditional absolute travel time of seismic waves but also the relative travel time difference between earthquakes. A new constraint is added to the seismic coda correlation time information. This new method uses simulated annealing method to find the minimum of the total residual error of the above three constraints to realize the inversion of the optimum position and the time of earthquake generation. On the basis of accurately constraining the relative position of the earthquake by using the traversing time difference between earthquakes, this method restricts the distance between the sources more accurately by constructing the cross-correlation waveforms of the superimposed coda waves between the seismic sources. The dependence of seismic location results on the location of the initial earthquake catalogue is weakened by the addition of absolute travel time of seismic waves. We apply this new method to the relocation of Lushan earthquake and aftershock and compare it with the popular program hypoDD. The results show that the relative position and absolute position of the earthquake can be more precisely constrained by the constraint of the correlation time of the superimposed coda wave and the addition of the absolute travel time of the seismic wave. In this paper, we use the new micro-seismic signal detection method-match and locate method) to detect the Lushan earthquake foreshock. By scanning the continuous waveforms six months before the earthquake, we found no small seismic signals outside the earthquake catalogue. Although there were some small earthquake events in the area near the epicenter before the Lushan earthquake occurred, there was no obvious increase in seismic activity in the region before the occurrence of the main earthquake. By comparing the aftershocks of the Lushan earthquake we find that there are a number of repeated earthquakes with high waveform similarity in the aftershocks which are usually of small magnitude and distributed along every region of the fault. The comparative analysis of the distribution of large aftershocks after large repeated earthquake swarm and high precision repositioning and the fracture slip model of limited fault inversion show that the aftershocks are mostly distributed in the areas with small slip amount around the main faults. At the same time, the rupture of the main fault may trigger the seismic activity of other faults in the surrounding area.
【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：P315

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