The March 7th 2005 Cavallerizzo (Cerzeto) landslide in Calabria - Southern Italy

In the early morning of March 7th 2005, after a period of prolonged rainfall (645 mm in 90 days, about 72% of mean annual precipitation) and snowfall, the hamlet of Cavallerizzo was severely damaged by a vast complex debris slide-earth flow. In total, thirty buildings were severely damaged or destroyed by the landslide, and the main road connecting Cavallerizzo with the villages of Cerzeto and Mongrassano was disrupted. About 310 inhabitants had to be evacuated to nearby villages. Several superimposed tectonic units, made of metamorphic rocks (Palaeozoic-Mesozoic) overlain by clastic terrains (Cenozoic-Neozoic), crop out in the vicinity of the study area. The main scarp of the slide developed at the eastern tectonic boundary of the Coastal Chain, marked by the "San Fili-Cerzeto-San Marco Argentano" recent (presumably active) N-S trending normal fault; its crown is mainly located within the cataclastic zone associated with such master fault. In the lower part of the landslide, two main earth-flows extended eastward along minor valleys, that merged down slope along the S. Nicola torrent. The sector affected by the landslide belongs to a wider large-scale slope movement, which extends westwards up to about 800 m a.s.l. The 2005 event is only the last paroxysmal episode of a long history of deformation recorded in the area of Cavallerizzo since the XVIII century. The area has been kept under control by the CNR-IRPI, by means of desultory field measurements (essentially, deep and superficial displacements, and piezometric levels) since 1999. Velocities, recorded at superficial benchmarks along opening cracks, pointed out "anomalous" conditions in the weeks preceding the collapse: pre-rupture velocities ranged from 0.8 to 5-6 cm/day. Despite its emergency character, the monitoring carried out helped to support civil-protection activities, and allowed all inhabitants to be saved.