Comparative tests of some multi-electrodic arrays using models of particular interest in engineering and environmental geophysics
by
Raffaele Martorana
CFTA Department, University of Palermo
Coauthors: Fiandaca G., Casas A., Cosentino P.L.

Modelling is a common practice in Applied Geophysics, especially when the problems are relatively new and/or the response of researched structures have to be tested under unusual conditions of energizing and measuring transducers.

Modelling is also an useful tool to compare the resolution power of different methodologies and/or arrays before to operate. In particular, different methods are today used for the electrical resistivity tomography (ERT) due to the fact that the electrical field can be applied to the subsoil in a lot of different ways and the responses can be observed in every points of the external surface, giving a set of pieces of information which have to be suitably integrated to obtain the tomographic “imaging”. The solution of the “inverse problem” can be strongly influenced by the geometry of the acquiring array and it can bring to interpretative models that can be very different depending on the electrodic array chosen.

In our case, we tested the response of two different models, which represent very common cases in studies of coastal hydrogeology (a sea-intrusion wedge) in engineering practice (buried foundations) and in archaeological researches (buried walls or similar remains). The two general models, with different geometrical shapes, are respectively characterized by three and four areas with different resistivity values.

A lot of simulations with synthetic models have been carried out, in order to compare the behavior of different arrays when acquiring ERT measures. For these models, apparent resistivity pseudosections have been calculated for the most common electrodic arrays (Wenner, Dipole-Dipole, Schlumberger, Wenner-Schlumberger). The obtained synthetic measures, after appropriate noising at different levels (2% and 5%), have been inverted using RES2DINV and RES3DINV software. The obtained interpretative models have been compared with the initial synthetic models using different parameters to estimate the quality of the matching.

Furthermore, a “no classical” configuration (the resistivity grid) has been also tested.

The results obtained using the various arrays have been compared. Consequently, the efficiency of the various arrays is evaluated for each problem, taking also into account some other characteristics of the arrays, including the associated practical advantages in time consuming and noise level.

Date received: September 13, 2004

Copyright © 2004 by the author(s). The author(s) of this document and the organizers of the conference have granted their consent to include this abstract in Atlas Conferences Inc. Document # caon-49.