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在台址下电阻率分层均匀的前提下,针对我国绝大多数前兆地电台单极距观测的事实与现状,提出一种试图从这种观测所获得的视电阻率时间序列中识别电阻率表层变化和深部变化的等效模型方法.分析表明,在保持布极方式和观测结果不变的前提下,任意多层的地电结构都可以视为一个二层地电结构——等效模型.本文中,等效模型上层的地电参数(电阻率和厚度)与实际模型第一层相同,下层的地电参数(电阻率)则根据等效要求,由实际模型第二层及其以下各层的地电参数经计算得到,因此,等效模型的下层包含了实际模型第二层及其以下各层的综合影响.初步研究表明,这种方法是可行的. 相似文献
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以唐山地震为例,研究分析了孕震过程中地电阻率各向异性度S的变化及其特征,同时用“流体-地电”的观战对S的变化进行了物理解释。结果表明,地电阻率各赂异性度有可能成为一种新的地震地电前兆因子。 相似文献
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本文基于测深反演结果, 通过数值模拟定性分析了地下水位和降雨对周至地电台地电阻率观测的影响; 同时利用褶积算法定量分析了降雨对该台NS向和NE向地电阻率观测的短期影响和长趋势影响.结果表明, 周至地电台地电阻率年变主要由地表薄层介质电阻率季节变化引起, 受地下水位变化影响不明显. 降雨对NS向和NE向地电阻率观测值的影响在短期内与观测结果一致, 表现为增加; 但长期趋势则与观测结果呈负相关关系.根据数值模拟分析认为, 这种变化与降雨及其渗透深度有关.分析结果与实际观测结果一致, 为正确认识周至地电台地电阻率观测与异常判定提供合理的理论依据. 相似文献
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根据电磁波的传播特性,把视电阻率随周期变化的曲线转化为电阻率随深度变化的曲线,并以此作为初始反演的地电模型.通过初始地电模型得到的视电阻率曲线与真实模型的视电阻率曲线的对比,对初始地电模型的电阻率值进行校正.校正后的反演模型的视电阻率曲线与真实模型的视电阻曲线的拟合程度有所提高.然后如此反复进行多次校正,获得与真实模型更为接近的反演模型,反演的拟合误差一般小于l%.模型试验和实际例子表明,该方法的拟合程度优于Bostick法. 相似文献
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本文研究了三层介质中膨胀球模拟震源的应力、应变场以及由这个应力、应变场产生的电阻率变化量和地表视电阻率变化的关系。结果表明,对于一定强度的“震源”,在地电装置探测范围内的应力场随具有不同弹性参数的层位有显著的变化;而应变场却看不出有明显的突变;由地表视电阻率变化量的计算结果揭示了地电异常受台站介质电性结构与力学结构的综合影响。因此作为预报地震的地电阻率法一方面要寻找具有高电阻率——应变灵敏度岩层的台址,另一方面台址的视电阻率变化对各层真电阻率变化要具有好的响应。 相似文献
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对兰州地电台1996 ~1998 年的地电阻率逐时值进行了计算处理,分析了地电阻率逐时值正常日变化特征.结果表明,兰州台地电阻率逐时值月平均日变化与年平均日变化存在较稳定的背景值.这一背景值可以作为判定地电阻率日变化短临异常的依据 相似文献
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观测地壳浅层电阻率随时间变化以寻找地震信息是地电阻率方法的目的。实际工作中,在保证观测精度的前提下,发现正常(无震)情况的地电阻率仍然存在着复杂的变化,给定量和定性分析地震异常带来相当大的困难。 本文分析了一些台站正常地电阻率的变化规律,并在此基础上提出“变化电性剖面模式”,来阐明一些台站正常地电阻率变化的复杂过程及其产生的可能原因。从此观点出发,导出以二层电性剖面为特征的台站正常地电阻率相对似年变化幅度公式。通过典型计算,提出获取平稳的正常原始资料是解决上述困难问题的方向,并指出了获取平稳正常变化资料的具体途径。 相似文献
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TSVI MEIDAV 《Geophysical Prospecting》1970,18(4):550-563
A number of electrical resistivity arrays are available to the exploration geophysicist in the conduct of vertical or horizontal profiling. The advantage of using central-type arrays which produce large potential drops, such as the Wenner or the Schlumberger, must be weighed against the ease of acentral arrays such as the polar and equatorial arrays. A series of nomograms has been designed to provide a means of rapid calculation of the potential drop to be obtained by any of the various central and acentral arrays, as a function of apparent resistivity, electrode spacings and available transmitter power. The same nomograms may also be used for approximate computation of the apparent resistivities in routine surveys. However, the accuracy of resistivity calculation is directly related to the accuracy of drawing lines between the scales and hence is rather limited in reduced-size nomograms in this paper. 相似文献
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本文对地电阻率法中两个常用的基本概念——勘探深度和探测范围进行了理论探讨和计算,分析了电法勘探中关于这两个概念的若干问题和不足。为了适应地电阻率法比较台址条件和研究其探测能力的需要,在分析这些问题的基础上,运用层状介质视电阻率的理论公式提出了勘探深度的新定义。用统一的标准给出了若干不同电性结构、不同装置下的勘探深度的定量结果,并具体讨论了探测范围上、下界面理论位置与介质表层及深部电性变化量大小、装置极距、仪器精度等参数之间的关系。指出在均匀介质、四极对称装置下,利用精度为1级的仪器探测下界面的最大深度可达极距AB的1.5倍左右的新结论,以及给出了加大探测范围的理论途径。最后本文还讨论了两个概念的差异和联系以及在一般非均匀介质条件下求得勘探深度的原则方法。 相似文献
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D. P. GHOSH 《Geophysical Prospecting》1971,19(2):192-217
Koefoed has given practical procedures of obtaining the layer parameters directly from the apparent resistivity sounding measurements by using the raised kernel function H(λ) as the intermediate step. However, it is felt that the first step of his method—namely the derivation of the H curve from the apparent resistivity curve—is relatively lengthy. In this paper a method is proposed of determining the resistivity transform T(λ), a function directly related to H(λ), from the resistivity field curve. It is shown that the apparent resistivity and the resistivity transform functions are linearily related to each other such that the principle of linear electric filter theory could be applied to obtain the latter from the former. Separate sets of filter coefficients have been worked out for the Schlumberger and the Wenner form of field procedures. The practical process of deriving the T curve simply amounts to running a weighted average of the sampled apparent resistivity field data with the pre-determined coefficients. The whole process could be graphically performed within an quarter of an hour with an accuracy of about 2%. 相似文献
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O. KOEFOED 《Geophysical Prospecting》1969,17(3):327-335
A mathematical analysis is given of the phenomenon of equivalence in resistivity sounding, which is based upon the properties of the raised kernel function. Analysis of this function instead of the apparent resistivity function is justified because, as has been shown in a previous publication, variations in the apparent resistivity function lead to variations in the raised kernel function with relative values of the same order of magnitude The expression for the raised kernel function is expanded into a Mac Laurin series. Equivalence can occur only if the second order term of this series is negligible. The coefficient of the first order term depends on the resistivity and the thickness of the layer under consideration. There is an infinite set of combinations of values for these two quantities, for which the coefficient of the first order term has the same value. All these combinations represent equivalent layer distributions. 相似文献
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