We investigate the applicability of offshore geoelectrical profiling in the littoral zone, e.g., for archaeological prospection, sediment classification and investigations on coastal ground water upwelling. We performed field measurements with a 20 m long multi-electrode streamer in inverse Schlumberger configuration, which we used to statistically evaluate measurement uncertainty and the reproducibility of offshore electric resistivity tomography. We compared floating and submerged electrodes, as well as stationary and towed measurements. We found out that apparent resistivity values can be determined with an accuracy of 1% to 5% (1σ) depending on the measurement setup under field conditions. Based on these values and focusing on typical meter-scale targets, we used synthetic resistivity models to theoretically investigate the tomographic resolution and depth penetration achievable near-beach underneath a column of brackish water of about 1 m depth. From the analysis, we conclude that offshore geoelectric sounding allows the mapping of archaeological stone settings. The material differentiation of low-porosity rock masses < 15% is critical. Submerged wooden objects show a significant resistivity contrast to sand and rocks. Distinguishing brine-saturated sandy sediments from cohesive silty-clayey sediments is difficult due to their equal or reversed resistivity contrasts. Submarine freshwater discharges in sandy aquifers can be localized well, though difficulties may occur if the seafloor encounters massive low-porosity rock masses. As to the measurement setups, submerged and floating electrodes differ in their spatial resolution. Whereas stone settings of 0.5 to 1 m can still be located with submerged electrodes within the uppermost 4 m underneath the seafloor, they have to be >2 m if floating electrodes are used. Therefore, we recommend using submerged electrodes, especially in archaeological prospection. Littoral geological and hydrogeological mapping is also feasible with floating electrodes in a more time-saving way.

中文翻译：

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逆斯伦贝谢阵列在浅水环境中对近地表目标的适用性

我们调查沿海地带的海上地电剖面图的适用性，例如，用于考古勘探，沉积物分类以及沿海地下水上升流的调查。我们使用反斯伦贝谢配置的20 m长多电极拖缆进行了野外测量，我们用它们来统计地评估测量不确定度和海上电阻率层析成像的可重复性。我们比较了浮动电极和浸没电极，以及固定和拖曳的测量值。我们发现视视电阻率值可以根据现场条件下的测量设置以1％至5％（1σ）的精度确定。根据这些值，并着眼于典型的电表规模目标，我们使用合成电阻率模型从理论上研究了在约1 m深度的微咸水柱下的近海滩可实现的层析成像分辨率和深度渗透。从分析中可以得出结论，海上地电测深可以绘制出考古石的背景图。<15％的低孔隙度岩体的材料区分至关重要。淹没的木制物体与沙子和岩石的电阻率明显不同。很难将饱和盐水的沙质沉积物与粘性粉质粘土沉积物区分开，因为它们的电阻率反差相等或相反。沙质含水层中的海底淡水排放可以很好地定位，尽管如果海底遇到大量的低孔隙度岩体可能会遇到困难。关于测量设置，浸没和漂浮电极的空间分辨率不同。尽管仍可以使用水下电极位于海床下方最上方4 m处的0.5至1 m的石块设置，但如果使用浮动电极，则必须大于2 m。因此，我们建议使用浸没电极，尤其是在考古勘探中。沿岸地质和水文地质填图也可以使用浮动电极以更节省时间的方式进行。