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题名	分层介质半空间瑞利波模式分析和介质参数反演
作者	鲁来玉
学位类别	博士
答辩日期	2004
授予单位	中国科学院声学研究所
授予地点	中国科学院声学研究所
关键词	瑞利波 层状半空间 频率波数分析 时频分析 反演 遗传算法
中文摘要	利用瑞利波信息反演层状半空间介质的性质和状态，是地震勘探、岩土工程、及超声检测领域关注的研究课题。本文由层状半空间瑞利波的实验数据，分析给出了层状半空间中瑞利波的传播模式和频散曲线，并进而利用基阶和（或）高阶模式瑞利波频散曲线反演了层状介质参数。本文分别用数值模拟和实验分析进行了深入的研究。在数值模拟中，采用地震勘探中常用的爆炸点源激发产生的瑞利波，利用频率波数分析方法分析了层状半空间瑞利波的频散，考察了源检距，道间距，接收道数目等因素对频散曲线的影响，给出了这些参数的定量要求。研究表明频率波数分析方法得到的频散曲线和按激发强度占主导的模式随频率的变化而形成的跳跃频散曲线一致。对于速度递增的层状半空间，反演时可以仅考虑基阶模式的瑞利波频散曲线，对于含有低速层的层状半空间，则必须考虑模式跳跃后形成的“之”字形频散曲线。在用遗传算法反演介质参数时，也必须考虑激发强度占主导地位的模式随频率的变化，从而恰当地设计目标函数，才能得出对层状介质参数的正确反演。在超声实验中，用表面圆形法向力源激发的瑞利波，对三个层状半空间模型，即均匀半空间，速度递增的两层半空间，含低速层的三层半空间，利用我们实验室自行研制的数字式多通道发射和接收系统，进行了超声探测实验。通过对实验得到的多道瑞利波信号，利用频率波数分析的方法得到了和理论结果一致的实验频散曲线，并基此利用遗传算法实现了层状介质参数的正确反演，得到了和实际介质参数相符的反演结果。数值模拟和实验研究的结果均表明，由实验数据正确给出频散曲线和相应的采用遗传算法发展的适合层状半空间介质的反演方法，是一种优良的反演方法，一般可以找到全局的最优解。获得介质性状较好反演结果的原因，是因为我们首次考虑到了由激发强度决定的占主导地位的模式随频率的变化规律，对应地我们建立了爆炸点源和表面法向力源激发下，分层半空间多模瑞利波模式分析及频散曲线获取和介质参数反演的系统方法。此外，本文最后为了与频率波数分析的结果进行对比，研究了时频分析方法一魏格纳维尔分布，用数值模拟和实验结果分析了层状介质中瑞利波的频散曲线。结果表明时频分析方法获得的频散曲线不及多道频率波数分析得到的瑞利波频散曲线准确。不过由于时频分析仅需要一个接收道的数据就能给出结果，比多道频率波数分析方法要简便，如果能对此方法加以改进，还是一种具有前景的分析方法。总的来说，本文系统地给出了用瑞利波反演分层半空间介质性质和层厚的方法，并给出了相应的软件。数值模拟和实验研究表明，本文给出的建立在严格理论基础上的方法，为用瑞利波探测地层和超声探测层状介质，奠定了可靠的基础。在此基础上，进一步发展相应的系统解释软件，可望能提供给地层勘探，层状材料和薄膜的超声探测等领域应用。
英文摘要	It is a topic in the fields of the seismic exploration, geo-technical engineering and the ultrasonic detection to inverse the properties of the stratified media in half space by using the Rayleigh waves. The propagation modes and dispersion curves of the Rayleigh waves are presented based on the analysis of the experimental data in stratified half-space media. The parameters of the stratified media are inversed by using the genetic algorithm (GA) based on the fundamental and/or higher modes of the Rayleigh waves observed. In this text, the numerical simulation and the experimental analysis are investigated in detail. In our numerical simulation, the Rayleigh waves were excited by the explosion of a point source. This method is widely used in the seismic exploration. The dispersion of the Rayleigh waves of the stratified media was analyzed with the method of the frequency-wavenumber (f-k) analysis. The observed dispersion curves were affected by the number and spacing of the receivers used, and the distance between the point source and the first receiver. Certain quantitative rules for these spacing and distance are given. It was shown that dispersion curves obtained using f-k analysis agreed with those mode-jumping dispersion curves derived from the change of the excited intensity dominated mode with the frequency. For the stratified media with S-wave velocity increment from the top to the bottom, it is good enough only to consider the fundamental mode in inversion. But for the stratified media with the low-velocity layer in between, the zigzag dispersion curves caused by the mode jumping must be considered. In the inversing the stratified media, the objective functions in the GA are selected properly also based on the relation of the excited intensity denominated modes to the frequency and the correct inversion results can be obtained. In our ultrasonic experiment, the Rayleigh waves were generated by a normal force disk source on the surface. Three stratified half-space models(homogeneous half-space, two-layered media with the S-wave velocity increment and the three-layered media with a middle layer of low-velocity) are investigated. All experiments were carried out in the digitalized multi-channel transceiver system developed by our laboratory. After the experimental data of the Rayleigh waves were processed by using the f-k analysis, the correct dispersion curves were obtained in good agreement with those from the theoretical prediction. And the parameters inversed by using the GA are in agreement with those of real media. Both the numerical simulations and the experimental results for the stratified media in half-space have demonstrated that the correct dispersion curves can be derived from the experimental data and our way of inversion based on the GA is a good method to find the optimized solutions. The reason obtaining the good inversion results briefly considers the change of the excited intensity dominated modes with frequency. The corresponding software can be used to analyze the multi-mode Rayleigh waves generated by the explosive point source or surface normal force-disk source and inverse the parameters of stratified media. In addition, Wigner-Ville distribution, one of the time-frequency analysis (TEA) methods, was also studied in comparison with the f-k analysis method to derive the dispersion curves of the Rayleigh waves in the stratified media numerically and experimentally. The results of the dispersion curves obtained from the TFA are not as good as those from the f-k analysis method. But the advantage of the TFA is that it only needs the data from one channel, and it is simpler than the f-k analysis method in which data from multi-channels are needed. If some improvement added, the TFA could be expected to be a promising method. All in all, the inversion method of the properties and the thickness of the stratified half-space media and the corresponding implementation software are presented in this text. Both the simulation and the experimental results show that our method based on the rigorous theory lays the solid foundation for the seismic exploration and the ultrasonic detection of Rayleigh waves in the stratified media. The further developed softwares are expected to find potential application in seismic exploration of the stratified half-space and ultrasonic detection of the stratified materials and films.
语种	中文
公开日期	2011-05-07
页码	160
内容类型	学位论文
源URL	[http://159.226.59.140/handle/311008/830]
专题	声学研究所_声学所博硕士学位论文_1981-2009博硕士学位论文
推荐引用方式 GB/T 7714	鲁来玉. 分层介质半空间瑞利波模式分析和介质参数反演[D]. 中国科学院声学研究所. 中国科学院声学研究所. 2004.

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