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利用小波分析方法对华北地区1990 年到1998 年的多台定点形变观测资料进行了分析计算,并将计算结果与该地区的地震活动进行了对比分析,同时讨论了不同阶的小波分解结果的物理意义及其与地震之间的对应关系。认为小波分解本质是窗口加权滑动平均,能有效地对各种不同频率成分的形变按不同的频段分离,为识别地震形变异常提供一种新的手段。在空间分布上,地形变的变化幅度与地震活动强度相对应,即在华北西北部地震活动性较强的包头、张家口一带,台站形变的强度明显高于华北东南部地震活动性较弱的泰安、营口等地区。在时间分布上,张北ML6 .2 级地震前大约两年东西方向的形变振幅随时间变化明显加大。 相似文献
114.
卫星重力测量技术的实现为测定地球动力学扁率提供了新的方式和途径,GRACE卫星是目前最新的重力测量卫星,据其恢复的低阶重力场较以往精度得到大大提高,然而其观测地球动力学扁率(二阶项)却与卫星激光测距(SLR)结果相差较大.本文采用最大熵谱和小波分析方法对GRACE和SLR观测的地球动力学扁率时间序列信号进行定量比较分析,结果表明:GRACE观测的地球动力学扁率年际周期变化振幅仅为SLR观测结果的25%,并且目前GRACE观测的地球动力学扁率数据中含有系统输入信息和相位差,但前者较后者包含有较强的短周期(2~6月)信息.造成这种差异的主要原因可能来自于GRACE与SLR全球观测数据时空分布不同. 相似文献
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This paper presents the closed‐form solutions for the elastic fields in two bonded rocks induced by rectangular loadings. Each of the two bonded rocks behaves as a transversely isotropic linear elastic solid of semi‐infinite extent. They are completely bonded together at a horizontal surface. The rectangular loadings are body forces along either vertical or horizontal directions and are uniformly applied on a rectangular area. The rectangular area is embedded in the two bonded rocks and is parallel to the horizontal interface. The classical integral transforms are used in the solution formulation, and the elastic solutions are expressed in the forms of elementary harmonic functions for the rectangular loadings. The stresses and displacements in the rocks induced by both the horizontal and vertical body forces are also presented. The numerical results illustrate the important effect of the anisotropic bimaterial properties on the stress and displacement fields. The solutions can be easily implemented for numerical calculations and applied to problems encountered in rock mechanics and engineering. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
117.
Abstract This paper experimentally investigates the convective planform near critical in a fluid layer whose temperature-dependent viscosity varies from top to bottom by up to a factor of 1500. Convection occurs in three different planforms: rolls, hexagons and squares. The square planform, which appears only for fluids with viscosity variation greater than about 50, replaces the hexagonal convection pattern as the Rayleigh number increases much above critical. The large amplitude of hexagonal convection with strong viscosity variation precludes studying the hexagon-square transition with perturbation methods of the type used to study the hexagon-roll transitions at smaller viscosity variations. 相似文献
118.
The Analytic Element Method (AEM) provides a convenient tool for groundwater flow analysis in unbounded continuous domains. The AEM is based on the superposition of analytic functions, known as elements, useful at both regional and local scales. In this study, analytic elements for strip aquifers are presented. Such aquifers occur in riverine or coastal deposits and in outcrop zones of confined aquifers. Local flow field is modelled indirectly, using a reference plane related to the aquifer domain through the Schwarz‐Christoffel transform. The regional flow is obtained as a solution of the one‐dimensional flow equation. The proposed methodology was tested by modelling two hypothetical situations, which were compared to exact solutions. It is shown that regional boundaries can be reproduced exactly while local fields are adequately reproduced with analytic elements. The developed elements are applied to simulate a real flow field in northeastern Brazil showing good agreement with measured water levels. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
119.
The Fourier Integral Method: An efficient spectral method for simulation of random fields 总被引:4,自引:0,他引:4
The Fourier Integral Method (FIM) of spectral simulation, adapted to generate realizations of a random function in one, two, or three dimensions, is shown to be an efficient technique of non-conditional geostatistical simulation. The main contribution is the use of the fast Fourier transform for both numerical calculus of the density spectral function and as generator of random finite multidimensional sequences with imposed covariance. Results obtained with the FIM are compared with those obtained by other classic methods: Shinozuka and Jan Method in 1D and Turning Bands Method in 2D and 3D, the points for and against different methodologies are discussed. Moreover, with the FIM the simulation of nested structures, one of which can be a nugget effect and the simulation of both zonal and geometric anisotropy is straightforward. All steps taken to implement the FIM methodology are discussed. 相似文献
120.
Detection of anomalous seismic phases by the wavelet transform 总被引:1,自引:0,他引:1
Kiyoshi Yomogida 《Geophysical Journal International》1994,116(1):119-130