【作者】 李宜晋；

【导师】 陈颙； 王宝善；

【作者基本信息】 中国地震局地球物理研究所 ， 固体地球物理学， 2011， 硕士

【摘要】 地球内部介质的结构及其变化对于了解地震孕育发生过程和地下应力变化,开展油气流动监测等具有重要意义。地球内部介质变化可通过地震波波速变化来反映。目前,利用人工震源激发地震波,进行地下介质监测已成为一个重要发展方向。基于观测基线长度的不同,介质波速变化人工震源监测的研究可以分为大、中、小等不同的尺度。相比于大尺度而言,小尺度介质波速变化的监测对测量精度要求更高。本文在前人研究的基础上,以提高介质波速变化监测精度为核心,分析了影响人工震源波速变化测量精度的因素,并以此为指导,构建了一套高精度小尺度地震波速变化观测系统,在北京市延庆县西拨子地震台开展了一年的连续观测实验,获得了该台站介质波速高精度观测结果,形成了几项关键技术。研究得出,影响波速变化测量精度的主要因素有：(1)震源能量与重复性；(2)信号采集时间触发精度；(3)波形的信噪比；(4)波速变化分析方法；(5)采集仪器性能；(6)观测系统布设与操作。利用超磁致伸缩超声震源和高速数据采集系统,构建了一套小尺度地震波速变化观测系统,该系统性能稳定,适于小尺度高精度地震波速变化观测。通过对连续观测实验数据的分析处理,得到：(1)超磁致伸缩材料震源是一种较为可靠的重复震源,相关系数可达0.999以上；(2)通过将采样率提高至10兆,大大减小了触发时间误差；(3)通过叠加、滤波和采用前置放大提高了观测波形的信噪比；(4)利用前后互相关使波速变化测量精度达到10-6；(5)波速变化观测结果与温度和大气压的变化具有良好的相关性。更多还原

【Abstract】 Knowing the inner earth structure and its variation in the medium has magnificent meaning to understand the seismogenic process, stress change in the subsurface, as well as oil and gas flow monitoring. Changes of the medium inside the earth can be reflected by seismic velocity change. Currently, using active sources to monitor underground medium has become an important study field. As base lines in observation are different, our study of seismic velocity change in the medium using active sources can be divided into three scales, from large to small. Compared to the large scale sources, it is more strict in the precision of seismic velocity change monitoring for small ones.Based on former study, this article aims at increasing precision of velocity change monitoring in the medium. We analyzed factors that influence the precision of seismic velocity change measurement, from which we construct a set of small scale seismic velocity change observation system with high precision. We also carried out an continuously observation experiment at Xi Bozi station in Yan Qing district, Beijing which last for about one year. Results of velocity change at the station with high precision are acquired, and several key techniques are done.Studies show that the main factors which influence the precision of the seismic velocity measurement are as follows:(1) Energy of the source and its repeatability; (2) Trigger precision of the sampling in time; (3) SNR of the wave forms; (4) Analysis of the wave forms; (5) Performance of the acquisition equipment; (6) Deployment and operation of the observation system.A set of small scale observation system for seismic velocity change monitoring has been constructed, using giant magneto striction transducer and high speed data acquisition equipment. The system is stable enough for the high precision observation of small scale seismic velocity change.Through analyzing and processing of the continuous observation data, we get the following conclusion:(1) Giant magneto striction transducer is a reliable repeat source, its correlation coefficient can be up to 0.999 and above; (2) By increasing the sample rate to 10M, the trigger error in time has greatly reduced; (3) SNR of the wave forms can be greatly increased by stacking, filtering and pre-amplifying; (4) The precision of seismic velocity change measurement can be up to 10-6 using Back and Front correlation; (5) The results of the seismic velocity change show good correlation to the temperature and atmosphere change.更多还原