Seismic response of a geological, historical and architectural site: the Gerace cliff (southern Italy)

Several historical towns and sites in Italy and other parts of Southern Europe were built on topographic reliefs, and they host inestimable cultural heritage. In Calabria (southern Italy), the historical town of Gerace is located in a highly seismic area and lies on top of an unstable cliff, constituted by a soft rock slab overlying a thick clay shale formation. A comprehensive study was carried out to reproduce the seismic response of the cliff and analyse potential effects due to severe earthquakes, such as those attributed by historical documents to the Calabrian seismic sequence that occurred in 1783. Much effort was spent on the geotechnical characterisation of the soils; in particular, a subsoil model was obtained by combining data from field and laboratory tests. The seismic response of the cliff due to the first event of the Calabrian sequence was simulated by 1D and 2D non-linear analyses, which enabled an assessment of the influence of topography on the seismic response. The 2D analyses justified the occurrence of large permanent deformations, as reported by the chronicles following the historical seismic sequence.