Georadar and passive seismic survey in the Roman Amphitheatre of Catania (Sicily)

A geophysical survey was performed at the Roman Amphitheatre of Catania with the aim to study the lithological features of the foundation subsoil of the Amphitheatre and to identify possible underground voids, buried crypts and other heterogeneities. The survey consisted of a number of georadar prospections and of three mechanical drillings. In addition it was experimented a non-invasive technique (passive seismic stratigraphy), which allows to retrieve information on subsoil stratigraphy and on possible seismic site effects. The survey allowed to establish 1) the presence of clays below superficial lava layers in the foundation soil of the Amphitheatre, 2) the presence of 2-D structures below the external ambulatory and 3) the natural resonance frequencies of the structure and of the subsoil in the area of investigation.