基于广义逆算法的层状弹性介质中瑞雷面波反演

【作者】 马翠莲；

【导师】 周竹生；

【作者基本信息】 中南大学 ， 地球探测与信息技术， 2008， 硕士

【摘要】 层状介质中的瑞雷面波不同于纵波和横波,它具有明显的频散特性,正是这一特性使得它能够在勘探及检测领域得到广泛的应用和研究。利用瑞雷波信息反演层状介质的性质和状态,是地震勘探、岩土工程领域关注的研究课题。反演问题是地球物理学的核心问题,它主要指根据观测到的数据,借助于正问题的数学模型,来求解地下介质的几何分布或物性参数分布。本文通过介绍和比较现有的线性及非线性反演方法,提出将广义逆算法反演应用于面波反演中的思想,通过计算和分析证实了该方法是可行且有效的。本文首先分别对各向同性介质、均匀半空间介质和层状介质进行了讨论,分析了瑞雷面波的频散特性。然后针对几种目前反演面波频散曲线常用的反演方法:最小二乘法、遗传算法、模拟退火法等,比较了这些方法的优缺点及反演的效果。引入一种线性反演方法——广义逆算法,采用标量传递算法对瑞雷波频散函数进行数值计算模拟得到频散曲线,作为反演的基础,再进行编程实现瑞雷波反演模拟,并与最小二乘法反演比较该方法具有收敛速度快且稳定的优点。最后采用τ-p变换法对面波提纯和常规Fourier变换来提取频散曲线,利用本文方法对衡邵高速公路的瞬态面波勘探的数据反演了路基地下速度结构,完整地实现了在实际勘探中面波反演的流程。总的来说,瑞雷波的反演研究是面波勘探领域中很重要的研究课题,反演解释方法的选择影响到地下介质性质及参数的准确性,也就直接关系到面波勘探的精度。由于地下介质的复杂性,可进一步发展复杂地层介质的反演方法的研究。更多还原

【Abstract】 Be different from the P wave and S wave in the layered medium, the Rayleigh surface wave (R wave) has the characteristic of frequency-dispersion, and is precisely this characteristic enables it to be able to the application of engineering geological exploration and engineering quality testing. It is a topic in the fields of the seismic exploration and geo-technical engineer to inverse the properties of the stratified in half space by using the Rayleigh waves. Inversion problem is the hard core in the geophysics, which is recurring to forward modeling and using the observational data to inverting the strata structure and the velocity parameter. Through the introduction and quite existing linear and the misalignment inversion method, this article proposes that the generalized counter algorithm inversion will apply in the surface wave inversion the thought.This article first separately discusses the isotropic medium, the even half space medium and the stratified medium, and analyzes the Rayleigh surface wave’s frequency dispersion characteristic. Then in view of several present inversion surface wave frequency dispersion curve commonly used inversion method: Least squares method (LSM), genetic algorithm (GA), simulation annealing (SA) and so on, compared with these method good and bad points and inversion effect. This paperintroduces one kind of linear inversion method------generalized counteralgorithm, used the scalar transmission algorithm to carry on the numerical calculus simulation to obtain the frequency dispersion curve., and carried on the programming to come true the Rayleigh surface wave inversion simulation. Compares with the least squares method inversion, this method has the convergence rate quick and the stable merit. The paper uses theτ-p transformation to purify surface wave depuration and the conventional Fourier transformation to pick up the frequency dispersion curve, does inversion about roadbed underground speed structure by the Heng-Shao highway’s Transient surface wave exploration data, and actualizes the surface wave inversion flow completely in the actual exploration.Generally speaking, the Rayleigh surface wave’s inversion research is in the surface wave exploration domain the very important research subject. The inversion explained that the method choice affects the accuracy of the underground medium nature and the parameter, and also directly has a relationship with precision of surface wave exploration. As a result of the underground medium’s complexity, we can develop the complex stratum medium inversion method research further.更多还原