High-Resolution Geophysics in Imaging and Characterization of Buried Cultural Heritage

Resolutionisacrucialparameterinpre-excavationsurveysofarchae- ological sites. Geophysical methods based on Laplace (gravity, magnetics), dif- fusion (e.g. low-frequency electromagnetics) and wave equations (i.e. seismics and ground-penetrating radar GPR) are often applied in this sequence to attain increasing detail about subsurface characteristics (i.e. shape and location of sub- surface volumes) and physical properties. We apply potential (magnetic gradiom- etry) and wave-equation based (i.e. seismics and GPR), combined with dedicated data-processing and analysis techniques based on instantaneous attributes, to the study of different archaeological sites, namely: an area characterized by scattered remains of unknown shape and dimension, a prehistoric grave, buried walls and foundations, a funerary tumulus. The depth range of interest is between 80 and 500 cm. Magnetic gradiometry, filtered to remove long wavelength anomalies and to focus the analysis on a +/- 5 nT range, allows clear identification of buried brick-walls, with unavoidable uncertainty concerning the depth of the targets. De- tailed 2-D and 3-D subsurface models come from the GPR results, where imaging of the buried structures can be combined with assessment of physical properties that affect wave velocity and attenuation. The combination of magnetic and radar methods in sequence is an effective strategy for high-resolution pre-excavation surveys: magnetic measurements allow rapid identification of localized anoma- lies, GPR provides higher resolution in their imaging and characterization. The application of attribute analysis techniques to GPR data further enhances the per- formance of the method in target identification. Peculiar archaeological targets, such as e.g. burial mounds, eventually require the use of transmission seismic to- mography to overcome the limits of potential and GPR methods.