Some considerations on the use of the geoelectric «square» array

Abstract

The «square array» is what we may consider to be an unconventional geoelectric configuration since it is not widely used and therefore there are few examples of practical application. The purpose of this research was to verify the operating effectiveness of this configuration in terms of profile and sounding, and the significance of the set of possible measurements and derived parameters. This was also obtained by comparing the relative measurements with the most common linear arrays (Wenner, Schlumberger, tripotential). The experiment was carried out in two different zones. In the first area, corresponding to the archaeological site of Marzabotto (Bologna), the target was represented by wall remnants inserted in a substantially homogeneous medium, from an electrical point of view, and at depths that are less than those of the dimensions of the device used. At the second site, located in the valley of Landrazza (Savona), the situation was very different, with a valley section on a calcareous bedrock filled with poorly classified residual sediments. An overall analysis of the results showed that the square technique is more exhaustive than the classical linear arrangements when performing soundings. Instead, with regard to profile development, it is not as preferred since it involves a greater amount of work without generating improved information. From analysis of the experimental results, considerable doubts arose about the meaning and the use of the anisotropy coefficients and the error term as defined theoretically. These parameters turned out to be of little use with regard to the characterization of the ground anisotropy and for checking the reliability of the measurements.