GNGTS 2016 - Atti del 35° Convegno Nazionale

564 GNGTS 2016 S essione 3.2 Processing of geophysical surveys in suburban and urban archaeological sites employing different integrated approaches E. Papale, S. Piro, D. Zamuner Istituto per le Tecnologie Applicate ai Beni Culturali. ITABC-CNR, Roma, Italy Introduction. The aim of archaeological prospections is to obtain information about the geometrical and physical characteristics of buried archaeological remains present at shallow depth in the ground. Generally, the limited size and depth of the archaeological remains, the presence of structures built with the same material as the surrounding rocks, soil inhomogeneity and environmental and anthropogenic disturbances, can be considered as “source” of noise which can cover the anomalies and contribute to acquisition of data with low S/N. It is possible to overcome these problems by improving data acquisition techniques (modern instruments allow the application of high resolution two dimensional and three dimensional acquisition techniques), by improving data processing methods through application of signal to noise enhancement techniques and by anomaly modelling. Another approach, which is discussed in this paper, involves the integration of data obtained with multiple geophysical methods (Brizzolari et al. , 1992; Piro et al. , 2000, 2016; Kvamme, 2007; Kucukdemirci et al. , 2015). Qualitative and quantitative integration techniques have been applied to data acquired in urban and suburban areas using the Ground Penetrating Radar (GPR) and the Electrical Resistivity Tomography (ERT) method. For the qualitative integration, graphical overlays and RGB colour composites have been applied to the datasets. Quantitative integration instead involves mathematical and statistical processes by which it is possible to merge the data acquired into one dataset. In this case we applied the mathematical approach of data sum and the statistical approach of Principal Component Analysis. These methods were used to process geophysical data collected in two sites in Italy; the first is situated in a suburban area in the Aurunci Natural Regional Park (Latina). The second site is instead located in an urban context in the city of Rome, near Santa Balbina’s church. The purpose of this work is to verify the applicability of some integration techniques of the data acquired with different methods and eventually to demonstrate the advantages of combining the geophysical methods used for this work. Investigated sites. Suburban Site (Appian Way, Fondi) . The area is situated along an ancient segment of the Via Appia, near the Gorge of St. Andrew (Gola di S. Andrea). The area is characterized by the presence of various archaeological features such as the well-preserved old basalt paving from the mid-Imperial period and the Fort of St. Andrew, which is a mixture of Roman, medieval and modern fortification that closed the way to the gulf. Moreover, there is proof of the presence of an ancient temple dedicated to the God Apollo, which has been dismantled over the centuries in order to build other structures such as the Fort of St. Andrew. The subsurface is also characterized by the presence of some archaeological features, such as a series of cisterns for water storage dating back to the III century B.C. Geologically, the sedimentary succession cropping out in the area belongs to the carbonate platform domain, and it consists of neritic carbonate deposits of upper Triassic to Upper Cretaceous age (Accordi et al. , 1988; Chiocchini et al. , 1977). Urban Site (Santa Balbina, Rome). The second investigated site is located in the central part of the city of Rome, near the Santa Balbina all’Aventino’s Church. There is not much archaeological information regarding this area, however it is suggested that there may be the presence of structures associated with the ServianWall (IVB.C.), and tuff quarries. In this area the stratigraphic succession is mainly characterized by the presence of the “Tufo Lionato” formation which consists of a lithified pyroclastic flow deposit from the Albani Volcanic Complex, overlaid by the alluvial sediments of the Aurelia Formation (Middle Pleistocene) (Funiciello et al. , 2008).