Comparative tests on different multi-electrode arrays using models in near-surface geophysics

Abstract

In this paper, the response of different synthetic models to geoelectrical multi-electrode surveys is studied. The models considered are related to two main problems, which are very common in geophysical research regarding hydrogeology and engineering. The first class of models represents buried walls, similar archaeological remains or remains of buried foundations; the other class corresponds to a sea-water intrusion of a fresh water aquifer, which is generally studied in hydrogeophysics. A set of 2D simulations, starting from the synthetic models, was carried out to compare the behaviour of the different arrays when acquiring measurements of electrical resistivity tomography. For each model, the apparent resistivity data—and relative pseudo-sections—were calculated for common electrode arrays (Wenner, dipole–dipole, Wenner–Schlumberger). Furthermore, a 'non-classical’ configuration (i.e. the linear grid) was also tested. The synthetic data, after adding different levels of Gaussian noise, were inverted using RES2DINV software; then the interpretative models were compared with the initial synthetic models using different parameters to estimate the quality of the matching. Finally, the comparison between the results obtained using the various arrays is presented. Furthermore, the effectiveness of the various arrays is evaluated for each problem, also taking into account some other characteristics of the arrays, including the associated practical advantages in time consumption and noise level. Results on synthetic data were also confirmed by two field tests: one at an archaeological site survey and one at a coastal aquifer study.