Electromagnetic tomography: consistency of images and groundwater prospecting     

冯锐  马奎祥  郭鸿  刘昌铨  孙次昌  郝锦绮 《地震学报(英文版)》1997,10(5):649-661

Ｅｌｅｃｔｒｏｍａｇｎｅｔｉｃｔｏｍｏｇｒａｐｈｙ：ｃｏｎｓｉｓｔｅｎｃｙｏｆｉｍａｇｅｓａｎｄｇｒｏｕｎｄｗａｔｅｒｐｒｏｓｐｅｃｔｉｎｇＲＵＩＦＥＮＧ１）（冯锐）ＫＵＩＸＩＡＮＧＭＡ２）（马奎祥）ＨＯＮＧＧＵＯ３）（郭鸿）ＣＨＡＮＧＱＵＡＮ...  相似文献   

电阻率层析成像的实质及其应用   总被引：5，自引：0，他引：5  

崔元星  张西荣 《水文地质工程地质》1997,24(2):58-60

电阻率层析成像技术是８０年代末期发展起来的一种地球物理勘探方法，本文分析了其实质，并介绍了用于电阻率层成像野外观测的ＭＣＯＨＭ－２１型仪器，最后通过实例说明了该方法的应用前景。  相似文献   

半空间地表反射式衍射CT   总被引：1，自引：0，他引：1  

陈柏鸿  朱文浩 《物探化探计算技术》1997,19(1):1-6

本文在半空间中。采用地表发射和地表接收的配置－地表反射式（ＳＲＰ），利用ＳＨ波进行衍射层析成象。在Ｂｏｒｎ近似下，导出反演公式并给出模型验算结果。此法属“滤波－反传播”算法一类。对于Ｎ×Ｎ图象的反演，主要用Ｎ次ＦＦＴ完成，不需要内插  相似文献   

Measuring surface-wave overtone phase velocities using a mode-branch stripping technique     

Hendrik Jan van  Heijst John Woodhouse 《Geophysical Journal International》1997,131(2):209-230

We present a method for the retrieval of the phase velocities of surface-wave overtones. The 'single-station' method is successful for several Love and Rayleigh overtone branches (up to at least four) in mode-specific period ranges between 40 and 200 s. It uses mode-branch cross-correlation functions and relies on adjusting the phase and amplitude of the mode branches one at a time. A standard statistical optimization technique is used. We discuss in detail the a priori information that is added to stabilize the retrieval procedure. In addition, we present a technique to estimate the reliability of individual phase and amplitude measurements. The retrieval method and the technique to estimate reliabilities can be used together in a highly automated way, making the methods especially suited for studying the large volume of digital data now available.
We include several applications to synthetic and recorded waveforms. We will discuss in detail an experiment with 90 waveforms that have travelled along very similar paths from Vanuatu to California. For this path, we will present average overtone phase velocities and an average 1-D velocity structure.  相似文献   

Sensitivities of seismic traveltimes and amplitudes in reflection tomography   总被引：2，自引：0，他引：2  

Yanghua Wang  R. Gerhard Pratt 《Geophysical Journal International》1997,131(3):618-642

Seismic traveltimes and amplitudes in reflection-seismic data show different dependences on the geometry of reflection interfaces, and on the variation of interval velocities. These dependences are revealed by eigenanalysis of the Hessian matrix, defined in terms of the Fréchet matrix and its adjoint associated with different norms chosen in the model space. The eigenvectors and eigenvalues of the Hessian clearly show that for reflection tomographic inversion, traveltime and amplitude data contain complementary information. Both for reflector-geometry and for interval-velocity variations, the traveltimes are sensitive to the model components with small wavenumbers, whereas the amplitudes are more sensitive to the components with high wavenumbers. The model resolution matrices, after the rejection of eigenvectors corresponding to small eigenvalues, give us some insight into how the addition of amplitude information could potentially contribute to the recovery of physical parameters.
In order to cooperatively invert seismic traveltimes and amplitudes simultaneously, we propose an empirical definition of the data covariance matrix which balances the relative sensitivities of different types of data. We investigate the cooperative use of both data types for, separately, interface-geometry and 2-D interval-velocity variations. In both cases we find that cooperative inversions can provide better solutions than those using traveltimes alone. The potential benefit of including amplitude-data constraints in seismic-reflection traveltime tomography is therefore that it may be possible to resolve the known ambiguity between the reflector-depth uncertainty and the interval-velocity uncertainty better.  相似文献   

Three-dimensional massively parallel electromagnetic inversion—II. Analysis of a crosswell electromagnetic experiment     

D. L. Alumbaugh  G. A. Newman 《Geophysical Journal International》1997,128(2):355-363

A 3-D electromagnetic inversion scheme has been successfully applied to crosswell electromagnetic data collected at the Richmond Field Station near Berkeley, California. By comparing images of data collected before and after the injection of 50000 gallons of salt water, a 3-D image of the plume has been developed, which shows the location of zones of maximum permeability surrounding the injection well through which the salt water has migrated. A resolution analysis has determined that the location of the plume is fairly accurate. However, the image of the geology will be distorted due to incomplete data coverage. This latter problem is further complicated by the fact that data residuals indicate that the wells deviate from the vertical. These deviations have been shown to cause artefacts within the images and thus further reduce the accuracy of the images with respect to the geology.  相似文献   

利用多种地球物理观测资料直接反演地幔对流模型   总被引：4，自引：3，他引：4       下载免费PDF全文

傅容珊  黄建华 《地球物理学报》1993,36(3):297-307

假定地幔为一个均匀的、粘滞系数为常数、同时均匀分布放射性热源的流体球层,其内部存在的对流则由流体力学3个基本方程:运动方程、能量方程和连续性方程确定.如果假定地幔处于低瑞利数的状态（临界瑞利数1.5倍左右）,那么上述方程中的非线性项可以忽略不计.作为一类可能的模型,本文计算一组用6个边界条件确定6个未知数的线性方程组.这些条件包括板块绝对运动极型场、地球大地水准面异常和地震层析结果提供的地幔密度分布横向不均匀相应的“刚性地球”水准面异常等.模型计算表明:1.地幔中流体运动格局不仅受地幔热动力学参数（瑞利数）控制,而且强烈地受边界条件的影响.2.若不限定下边界为等温边界,则上、下地幔之间并不呈现出活动性明显差异;但是在模型瑞利数加大到一定值时,核-幔边界附近将出现一些局部的小尺度对流环.3.当模型瑞利数从很小增加时,对流格局将发生变化,这些格局可能反应由地幔热动力学参数决定的地幔固有特性.4.当瑞利数为50000和80000时,核-幔边界形变与PcP波得到的结果吻合较好.  相似文献   

井间电磁波CT中的非块体分段反演算法   总被引：1，自引：0，他引：1  

吴建平  冯锐 《CT理论与应用研究》1993,(3)

本文给出了用网格节点表示的介质中直射线追踪的算法。在实际工作中,我们常发现当井间CT 应用于强不均匀体存在的区域时,反演结果往往会严重失真,为了解决这一问题,我们采用对测量数据分段反演的新算法。首先利用强信号(即弱衰减)确定衰减量较小的背景介质的衰减系数,固定背景介质的衰减系数(或对其加入强约束),然后逐渐用较弱的信号确定衰减系数较大的介质在井间的分布,直至反演出整个井间的吸收系数分布。实践表明,当强不均匀体存在时,运用这一方法得到的结果明显优于不作分段时得到的结果。  相似文献   

井间地震射线层析成像   总被引：3，自引：0，他引：3  

鲁传恒  顾贤明 《CT理论与应用研究》1994,3(3):18-25

本文采用射线走时对井间介质的地震波速进行层析成像，反演出井间介质的异常分布和构造．作者用快速弯曲射线迫踪法求解初值问题，用两步法和插值逼近法结合求解两点问题，避免了复杂运算，提高了运算效率和精度．反问题的数值计算用ＬＳＱＲ法．为了求取速度任意分布、对比度大的较为复杂介质模型的槽确初至时，本文采用动态程序法。该法灵活不受地质界面条件约束，且对介质速度分布未加任何限制。本文给出了几个算例．文中层析成像试验结果表明，此种层析成像算法是成功和有效的。  相似文献   

Comparison of global waveform inversions with and without considering cross-branch modal coupling   总被引：1，自引：0，他引：1  

Xiang-Dong Li  Barbara Romanowicz 《Geophysical Journal International》1995,121(3):695-709

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