Abstract

Static distortions are known abroad by the term “static shift distortions.” They have a strong influence on the results of deep electromagnetic soundings made with both natural (AMT-MTS) and controlled (CSAMT) sources. The main cause of static shift distortions is the local inhomogeneities of the upper half-space in comparison with the electromagnetic wavelength in the ground. Static shift distortions are frequency-independent and manifest themselves in a parallel shift of the apparent resistivity curves relative to the resistance scale. The shape of the apparent resistivity curves containing information on the section of the model is preserved, but the ideas about the depths of the layer locations and their conductance values change. Currently, many methods have been developed for quantifying static shift distortions, but they all have a quality, phenomenological character. This work proposes a quantitative method for the correction of static shift distortions. It is based on the use of the apparent resistivity curve of a controlled source, normalized to the value of the total horizontal magnetic field. The use of magnetic measurements with induction coils that do not have a galvanic connection with the ground allows quantifying static shift distortions by comparing the magnetic field with apparent resistivity curves normalized to the total electric field or the total input impedance value. The proposed method is applicable only for frequency soundings with controlled sources CSAMT. Nevertheless, it allows one to correct the MTS and AMTS curves measured at the same installation and using the same sensors in the low-frequency region, outside the wave zone, where the CSAMT method loses its sounding functions. The results of the experimental works that justify the applicability of the new method by the example of controlled-source soundings are presented.

中文翻译：

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一种使用受控源磁场（CSAMT）量化静态偏移失真的方法

摘要

静态失真在国外被称为“静态位移失真”。它们对使用自然声源（AMT-MTS）和受控声源（CSAMT）进行深电磁测深的结果有很大的影响。静态位移失真的主要原因是与地面电磁波相比，上半空间的局部不均匀性。静态偏移畸变与频率无关，并且在视在电阻率曲线相对于电阻刻度的平行偏移中表现出来。保留了包含模型截面信息的表观电阻率曲线的形状，但有关层位置深度及其电导值的观念却发生了变化。目前，已经开发出许多方法来量化静态偏移失真，但是它们都有很好的质量，现象学特征。这项工作提出了一种用于校正静态偏移失真的定量方法。它基于受控源的视在电阻率曲线的使用，该曲线被归一化为总水平磁场的值。将电磁测量与不与地面进行电流连接的感应线圈配合使用，可以通过将磁场与归一化为总电场或总输入阻抗值的视在电阻率曲线进行比较，来量化静态位移失真。所提出的方法仅适用于具有受控源CSAMT的频率探测。尽管如此，它仍然可以校正在相同安装位置和使用相同传感器，在波区之外的低频区域中测量的MTS和AMTS曲线，CSAMT方法失去了其探测功能。给出了实验结果，以控制源探测为例，证明了该新方法的适用性。