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本文讨论了任意N层平面分层,每层又可具有任意柱面分层的轴对称二维非均匀有耗介质结构,分析电磁波在其中的传播、散射特性.由于采用电磁场的数值模式匹配理论,径向用离散数值本征模式替代连续模,纵向则用模式匹配方法导出场递推关系的解析表达式,大大减少了数值计算量,而计算精度不变.场的数值结果可很好的再现地下电参数剖面.相应的数值分析程序可用于从感应测井到电磁波测井的计算机辅助解释. 相似文献
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地震波场模拟和偏移成像等有限差分隐格式算法中的重要环节，是实现亥姆霍兹算子表示矩阵H的快速求逆运算. 在螺旋边界条件下，H具有Toeplitz结构的正定厄密矩阵，其快速求逆可由谱法LU分解实现. 本文分析了谱法LU分解对提高计算速度的原理及特点，并着重讨论了在不同类型的介质模型中，采用谱法分解矩阵H时带来的数值误差、误差的分布及其对波场计算的影响. 研究结果表明，对均匀介质而言，矩阵H各列具有相同的非零元素分布，谱法LU分解的误差在吸收边界条件下，不影响波场模拟和成像计算；但对于非均匀介质模型，矩阵H各列具有不同的非零元素分布，谱法LU分解的误差随介质不均匀性程度的增大而增大，势必影响非均匀介质中波场计算. 在波场模拟和成像等有限差分隐格式算法中，采用谱法LU分解完成矩阵求逆时，必须考虑到并尽量减少该方法的误差对波场计算的影响. 相似文献
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从分层均匀介质中地震波传播的基本理论出发, 参考已有的利用广义反射透射系数矩阵方法计算分层均匀介质中点源引起的地面运动的方法和程序, 考虑了任意几何特征的有限震源及有限震源的震源机制随时间和空间发生变化的可能性, 并考虑了并行计算的发展方向, 本文对点源情况下的计算流程进行了改进, 重新设计编写了计算程序GRTMatSyn, 使其不但适应于点源的情形, 也适应于任意几何形状的、 有限的、 震源机制随时间和空间变化的有限震源的情形． 为了验证该程序的可靠性和计算效率, 设计了必要的有限震源模型和观测点分布, 计算了地面运动, 并与已有的被广泛认可的计算有限平面断层引起的地面运动的程序CompSyn的计算结果进行了对比分析． 结果表明, GRTMatSyn的计算结果可靠、 计算效率较高． 相似文献
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横观各向同性层状半空间中的弹性位错 总被引：1，自引：0，他引：1
本文在柱向量函数系下,利用传播矩阵法求解了层状横观各向同性半空间由内部点源位锚引起的变形;对六个基本点源位错,以等价体力法推出了横观各向同性情形下的点源函数,并且给出了内部任意剪切位错源引起的地表位移的积分表达式。为研究地球的层状结构,特别是其上部的横观各向同性对地表的地震位移、应变以及倾斜场的影响提供了计算公式。 相似文献
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点源两层大地三维地电模型视电阻率边界元解 总被引：2，自引：1，他引：2
本文用两层均匀大地人工点源作用下的空间电位分布作为基本解，导出了下伏基岩中陷含三维地质体情况下，关于电位的边界积分方程组，用边界单元法解积分方程求得地表电位，从而求得了一定装置下的视电阻率。本文方法的独特优点是积分只须在异常体边界面上进行了测线可以沿任意方向。用联剖法计算了均匀半空间下含球形异常体的ρｓ曲线，所得结果与其他学者用解析方法所求得的结果一致。用中间梯度法计算下层基岩中含有一长方体，测线 相似文献
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应用混合变量弹性动力学方程和线性常微分方程组的矩阵指数解法，将层状介质中广泛应用的弹性波传播矩阵解法推广至横向非均匀介质，给出了一种可计算复杂地质体中弹性波传播的广义传播矩阵数值解法。该方法可模拟任意震源及所产生的各种体波、面波，数值结果表明具有很高的计算精度。 相似文献
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本文利用最近开发的孔隙介质震电波场算法开展了数值模拟研究,重点探讨不同结构模型中双力偶点源以及有限断层面源作用下产生的地震波及其伴随的电磁信号的时域和频域特征,考察了不同震源时间函数类型对震电波场数值模拟结果的影响,并以Ricker子波为例讨论了震电波场的频率响应特征.结果表明:地震电磁信号的波形、振幅和持续时间等都不同程度受到模型结构的影响,结构越复杂,波形也越复杂;不同震源(双力偶点源与有限断层面源、震源时间函数类型、Ricker子波峰值频率)产生的位移场和电磁场在波形和频谱响应方面整体上呈现相似的特征,但在波形和频谱的幅度和复杂程度方面存在一定差异. 相似文献
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Paraxial ray methods have found broad applications in the seismic ray method and in numerical modelling and interpretation
of high-frequency seismic wave fields propagating in inhomogeneous, isotropic or anisotropic structures. The basic procedure
in paraxial ray methods consists in dynamic ray tracing. We derive the initial conditions for dynamic ray equations in Cartesian
coordinates, for rays initiated at three types of initial manifolds given in a three-dimensional medium: 1) curved surfaces
(surface source), 2) isolated points (point source), and 3) curved, planar and non-planar lines (line source). These initial
conditions are very general, valid for homogeneous or inhomogeneous, isotropic or anisotropic media, and for both a constant
and a variable initial travel time along the initial manifold. The results presented in the paper considerably extend the
possible applications of the paraxial ray method. 相似文献
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I.R. MUFTI 《Geophysical Prospecting》1980,28(1):146-166
The problem of numerical evaluation of apparent resistivity curves is treated by finite difference modeling. The models proposed are set up in cylindrical coordinates and yield the potential field due to a point source located in a radially symmetric environment. The Schlumberger configuration, widely used for surface measurements, is emphasized. However, the treatment is equally applicable to other similar situations such as the computation of synthetic electric logs when the resistivity of the borehole fluid is different from that of the surrounding uniform or stratified medium. Moreover, the individual layers may not necessarily be isotropic. The medium under investigation is discretized by using a very coarse system of horizontal and vertical grid lines whose distance from the source increases logarithmically; consequently, the physical dimensions of the medium can be made “infinite” without affecting the numerical size of the model. Finer features such as a thin but anomalously resistive or conductive bed which would ordinarily be missed in coarse discretization are accurately taken into account, since the calculations are done in terms of the Dar Zarrouk parameters derived from the exact resistivity distribution of the model. This enables one to compute the potential field by inverting a small sparse matrix. When the medium comprises only a few layers, the efficiency of the finite-difference model is comparable to that of the known analytical methods; for more complicated structures, however, the finite-difference model becomes more efficient. The accuracy of finite-difference results is demonstrated by comparing them with the corresponding analytically obtained data. 相似文献
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M. A. MEKONNEN B. DARGAHI 《国际泥沙研究》2007,22(3):188-198
The 3D numerical model, ECOMSED (open source code), was used to simulate flow and sediment transport in rivers. The model has a long history of successful applications to oceanic, coastal and estuarine waters. Improvements in the advection scheme, treatment of river roughness parameterization and shear stress partitioning were necessary to reproduce realistic and comparable results in a river application. To account for the dynamics of the mobile bed boundary, a model for the bed load transport was included in the code. The model reproduced observed secondary currents, bed shear stress distribution and erosion-deposition patterns on a curved channel. The model also successfully predicted the general flow patterns and sediment transport characteristics of a 1-km long reach of the River Klar?lven, located in the north of the county of V?rmland, Sweden. 相似文献
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Jianjun ZHOU 《国际泥沙研究》2003,(2)
1 INTRODUCTION The Lower Yellow River starts from Huayuanko and runs on a plain for about 800 km before emptying into the Bohai Sea. The river is notorious for its extremely heavy sediment load, 1.6 billion tons annually with a relatively small runoff of only 41 km3 at the river mouth. Such a huge volume of sediment is partly deposited in the channel and partly discharged through the estuary into the Bohai Sea. As the tide nearby is weak, a bulk of the sediment cannot be brought to th… 相似文献
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《Advances in water resources》2007,30(4):730-741
In this work the numerical integration of 1D shallow water equations (SWE) over movable bed is performed using a well-balanced central weighted essentially non-oscillatory (CWENO) scheme, fourth-order accurate in space and in time. Time accuracy is obtained following a Runge–Kutta (RK) procedure, coupled with its natural continuous extension (NCE). Spatial accuracy is obtained using WENO reconstructions of conservative variables and of flux and bed derivatives. An original treatment for bed slope source term, which maintains the established order of accuracy and satisfies the property of exactly preserving the quiescent flow (C-property), is introduced in the scheme. This treatment consists of two procedures. The former involves the evaluation of the point-values of the flux derivative, considered as a whole with the bed slope source term. The latter involves the spatial integration of the source term, analytically manipulated to take advantage from the expected regularity of the free surface elevation. The high accuracy of the scheme allows to obtain good results using coarse grids, with consequent gain in terms of computational effort. The well-balancing of the scheme allows to reproduce small perturbations of the free surface and of the bottom otherwise of the same order of magnitude of the numerical errors induced by the non-balancing. The accuracy, the well-balancing and the good resolution of the model in reproducing free surface flow over movable bed are tested over analytical solutions and over numerical results available in literature. 相似文献
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Point source reflection/transmission responses from planar interfaces based on the Sommerfeld-Weyl integral are causal and are given in the form of a solution integral with an infinite integration limit. They can be simply transformed to integrals with a finite limit by an approach that takes into account causality as well as time-symmetry aspects. To introduce the fundamental principles involved, the transformation is applied to the simple case of a point-source response from a planar acoustic interface. For a point source above a planar interface separating an upper and lower acoustic half-space of velocity c1and c2 the inhomogeneous plane waves in the Sommerfeld-Weyl source representation do not contribute to the final result if c1≤c2 and only a limited spectrum of inhomogeneous plane waves comes into play if c1c2. 相似文献
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自从发现震电现象以来,众多学者进行了相关研究.其中,Pride提出了一套描述流体饱和孔隙介质中震电波场的耦合与传播的宏观控制方程组,该方程组后来被广泛地应用到相关的震电研究中.Chen发展了一套广义反透射系数方法并将其应用到层状介质合成地震图的研究当中,该方法数值计算效率高并且可以处理带弯曲界面层状介质这种复杂模型.基于Pride的震电波场控制方程组,我们将Chen的广义反透射系数方法推广应用到层状孔隙介质中震电波场的数值模拟研究中,但是在数值计算过程中发现,当含源层的厚度相对于地震波波长较大时（即高频情况）,会出现数值计算的不稳定,此即为高频不稳定性问题.针对高频不稳定性问题,一种自然的处理方法就是在原来的含源层中插入两个虚拟界面,构造出一个新的含源薄层,但是这会带来一些额外的计算量,此外,由于虚拟含源薄层的厚度是有限的,必须针对具体模型参数设定一个合适的厚度值.高频不稳定性问题同样存在于层状介质合成地震图的数值计算过程中,Chen提出了一种解析的处理方法,即在原含源层内引入一无限薄的虚拟含源薄层,通过解析的方法解决高频不稳定性问题,该方法不会降低计算效率且适用于任意参数模型.本文首先对层状孔隙介质中的震电波场数值计算公式进行分析,指出源项积分中的指数增长因子是导致高频不稳定性问题的根本原因;其次将Chen在合成地震图数值模拟研究中采用的解析处理方法推广到震电波场研究中,得到了适用于数值计算的公式;然后给出数值算例,并针对一个含源层过厚的模型,比较了自然处理方法和解析处理方法,两种方法得到的结果具有相当好的一致性,而解析处理方法计算效率更高,证实了本文给出的解析处理方法在解决层状孔隙介质震电波场数值模拟的高频不稳定性问题方面的有效性. 相似文献