GEOPHYSICAL PROSPECTION USING HIGH-RESOLUTION ELECTRICAL TOMOGRAPHY TECHNIQUE APPLIED TO ARCHAEOLOGICAL SITE INVESTIGATION. APPLICATION TO THE TINANION PARK AREA (PEIREAS)

• P. Tsourlos, G. Tsokas (Geophysical Laboratory, Dept. of Geology, Aristotle University of Thessaloniki, 541 24 Thessaloniki, Greece)
• G. Stainhower (B'Ephoreia of Prehistoric and Classical Antiquities, Polignotou 13, 105 55 Athens, Greece)

In this work a high-resolution geophysical survey using the electrical tomography technique applied to archaeological site investigation is presented. The technique was applied to the area of the Tinanion Park at the Peireas city center.

Electrical tomography measurements were collected on a dense grid using the Wenner-Schlumberger array with inter-electrode distance of a=0.6m and maximum AM separation of n=8a. A total of 44 resistivity lines were measured (more than 12000 measurements) using a fully automated resistivity meter.

Data were processed with the use of a 2-D non-linear inversion algorithm, which performs iterative optimization based on a finite element forward modeling scheme. All inversions produced good fits (RMS error 2-7%) and thus we assume that the produced results depict a realistic image of the subsurface resistivity.

By appropriately combining the 2-D inversion results we were able to produce cross-sectional images of the subsurface resistivity at various depths, as well as fully three-dimensional resistivity pictures.

High resistivity structures were located at relatively low depths, which are probably related to wall structures. A deeper high resistivity almost cubical feature at the West part of the survey area is of particular interest and was interpreted as possible tank or storage settlement.

We conclude that by using high-resolution electrical tomography techniques, as opposed to the traditional electrical mapping, we are able to obtain important information concerning the exact dimensions, burial depth and shape of the subsurface structures. Additionally, this information is directly appreciable and interpretable by non-geophysical experts (i.e. archaeologist). This renders the present technique particular useful to the geophysical investigation of the archaeological sites despite it increased cost.