Resistivity Tomography Imaging of the Substratum of the Bedestan Monumental Complex at Nicosia, Cyprus

Abstract

In the framework of the EU-UNDP project 'Rehabilitation of Old Nicosia' (Cyprus, 2004-9), a high-resolution geoelectrical survey has been performed inside the partially ruined monumental complex of St Nicholas of the English, now called the Bedestan, which was designed to become a venue space for cultural activities. The aim was to detect buried traces of a Byzantine basilica of the sixth century, on the ruins of which, according to tradition, the construction of St Nicholas was begun in the 12th century. The survey has been conducted on the floor of the monument, using a dipole-dipole electrode array along two perpendicular sets of profiles. In order to model the resistivity distribution, the probability-based electrical resistivity tomography inversion (PERTI) method has been applied. Sets of aligned blocks with resistivity in the range 100-400 ohm·m, bounding a three-room rectangular space, and traces of a rounded structure with mean resistivity about 150 ohm·m, appearing at one extremity of the central room, are the main resistive features recognized down to 4 m depth, within a conductive background with resistivity in the range 20-40 ohm·m. Altogether, these resistive features, showing in plan the shape of a church characterized by a central nave with an apse and two side aisles, have been interpreted as an evidence of the existence of remains of the earlier Byzantine basilica. Moreover, small volumes with resistivity in the range 10-12.6 ohm·m have been found, scattered underneath the whole surveyed area. Taking into account the PERTI results, ground-truth has been performed in two sites, designed to become two permanent protected exposures of the archaeological findings beneath the floor of the newly restored Bedestan. At one site, excavations detected remains of masonry in correspondence of the alignment of resistive blocks at the left margin of the left side aisle of the churchlike structure. At the other site, graves, entirely filled with wet debris in an alluvial soil matrix, have, instead, been found in correspondence with the greatest conductive volume, detected outside the perimeter of the churchlike structure. Both findings have been dated back to the sixth century. Since the Bedestan case-history is one of the first applications of the PERTI algorithm to real field data sets, its performance has been tested using the well-known ERTLab TM commercial software as benchmark. The comparison has shown a general consistency between the two inversions, and also confirmed the much higher computing speed, better filtering capacity and greater versatility of the PERTI algorithm, already outlined in a previous paper where only synthetic models were tested.

A Multidisciplinary Approach to the Study of the Temple of Athena in Poseidonia-Paestum (Southern Italy): New Geomorphological, Geophysical and Archaeological Data

“…In our case, we applied the probability-based ERT inversion (PERTI) method [34], derived directly from the principles of probability tomography [35,36]. As outlined in previous applications [37][38][39][40][41], the PERTI method can be considered a self-sufficient procedure, useful as a means of determining the location and shape of the most probable sources of the anomalies detected on the ground surface.…”

A Probability Electrical Resistivity Tomography Imaging of complex tectonic features in the Kissamos and Paleohora urban areas, Western Crete (Greece).

“…As outlined in previous applications [Amato et. al., 2016;Compare et al, 2009aCompare et al, , 2009bCozzolino et al, 2012Cozzolino et al, , 2014Rose et al, 2015], the PERTI method can be considered a self-sufficient procedure, useful to delineate location and shape of the most probable sources of the anomalies detected on the ground surface. The independence from a priori information, the absence of iterative processes, the drastic reduction of computing time with respect to standard deterministic inversion tools, the independence from data acquisition techniques and spatial regularity, the capability to resolve complex continuous resistivity variation make the PERTI algorithm a versatile and objective approach.…”

“…In the following sections, we report a short outline of PERTI method [Mauriello and Patella, 2009] as described in Cozzolino et al [2014], we describe at first the geological background of Kissamos and Paleohora basins and the ERT acquisition plan, then the PERTI results, the results obtained using the renowned RES2Dinv inversion software (www.geotomosoft.com) and their comparison.…”

An integrated quantitative approach to assess the archaeological heritage in highly anthropized areas: the case study of Aesernia (southern Italy)

“…The main features of this method are: unnecessity of a priori information; full, unconstrained adaptability to any kind of dataset, drastic reduction of computing time of even two orders of magnitude with respect to standard deterministic inversion tools, independence from data acquisition techniques and spatial regularity, capability to resolve complex continuous resistivity variation. Many field cases were dealt with using this approach [25]- [30], and in all cases the procedure proved a reliable tool for the most probable locations of the sources of the measured apparent resistivity anomalies to be highlighted at the appropriate depths.…”