LANDSLIDE EFFECTS IN A HISTORIC SICILIAN TOWN
LANDSLIDE EFFECTS IN A HISTORIC SICILIAN TOWN

Summary/Abstract: The town of Agrigento is set in a physically fragile environment between unstable slopes and ancient structures in urgent need of conservation and restoration. Geomorphological studies were performed for the analysis and monitoring of the landslide involving the historic area of Agrigento (Italy), whose stability is threatened by retrogressive landslide processes. Up to 2-5 mm/year displacement are observed in 1992-2008 on the staircase and the lift aisle of the ancient Cathedral of the town (11th Century). Displacement acceleration to 13-15 mm/yr is measured in July 2006-May 2007. The areas moving at higher rates, located at the edge of the NW slope of Agrigento hill, which is made by a typical transgressive succession of a sandy-clay sequence with various calcarenite bodies (Agrigento formation). This sequence are probably discontinuously, on clay soils from the Middle-Upper Pliocene (Monte Narbone Formation). The area has been unstable since 1315, involving both the little-welded, very porous and fractured calcarenitic sections (E-W) from Pleistocene and the clay layers interstratified within these sections. Since 1924, from time to time, various typologies of disruption have occurred: falls, flows and more complex phenomena. From 2007 until now the collapse has been the object of several studies that used different research techniques (interferometric, aerial and satellite images analysis, geognostic and geo-physical surveys, etc.) as well as of a permanent monitoring activity. In order to rebuilding the geological model and identifying the typology of the landslide phenomenon, we analyzed all the available data. This analysis will be support to the most suitable solution to mitigate the risk and safeguard the monuments and houses located in this area.

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