Abstract

When solving many geophysical problems, vertical electrical sounding (VES) monitoring is used on stationary multielectrode installations. The resulting time series of observations can be considered as the VES profile (set of markers), deployed not in space, as with profile soundings, but in time. When solving the VES inverse problem for precision monitoring data on a stationary multielectrode VES array, the effect of a high-amplitude antiphase change in the resistivity of adjacent layers with time was discovered. This behavior is physically unlikely. To clarify the causes of this phenomenon, synthetic VES profiles, similar to real ones, were studied. In each layer of the model section, the law of the change (along the profile) in resistivity with time was set and synthetic curves of apparent resistivity were calculated. Then the VES inverse problem was solved. In this case, the same algorithms were used as for the experimental series. The obtained solutions were compared with the original synthetic resistivity profiles, which made it possible to analyze errors in the solution. The results showed that the effect of the antiphase change in resistivity of adjacent layers of the section (the swing effect in solving the inverse problem) is not associated with real changes in resistivity. It arises due to the special structure of the landscape of the discrepancy due to the equivalence in resistivity. This feature is not taken into account by standard algorithms for solving the inverse problem and can lead to rather large errors if no special countermeasures are taken. When monitoring a geoelectric section, increased requirements are imposed on the accuracy of solving the VES inverse problem. The required accuracy cannot be achieved with commonly used inversion algorithms. It is necessary to develop special algorithms for selecting a solution to the inverse problem that suppresses swing.

中文翻译：

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解决垂直电测深反问题中的不稳定性特征

摘要

解决许多地球物理问题时，在固定式多电极设备上使用垂直电声（VES）监视。观测结果的时间序列可以看作是VES剖面（一组标记），与剖面测深不同，它不在空间中部署，而是在时间上部署。当解决用于固定多电极VES阵列上的精确监视数据的VES反问题时，发现相邻层电阻率随时间的高振幅反相变化的影响。这种行为在物理上是不太可能的。为了弄清这种现象的原因，研究了类似于真实VES的合成VES轮廓。在模型截面的每一层中，设定电阻率随时间的变化规律（沿剖面），并计算视电阻率的合成曲线。然后解决了VES反问题。在这种情况下，使用与实验系列相同的算法。将获得的溶液与原始的合成电阻率曲线进行比较，从而可以分析溶液中的误差。结果表明，该部分相邻层电阻率的反相变化的影响（解决反问题中的摆动效应）与电阻率的实际变化无关。它是由于电阻率相等而导致的差异景观的特殊结构而出现的。解决反问题的标准算法未考虑此功能，如果不采取特殊对策，则会导致较大的错误。监视地电部分时，对解决VES反问题的准确性提出了更高的要求。使用常用的反演算法无法达到所需的精度。有必要开发特殊的算法来选择抑制摆动的反问题的解决方案。