Page 3 - Falconi_et_al_2017

124 L. Falconi et al.

1700 and 1950 (Fiora and Alciati 2008). Many buildings surrounded by 33 km of indented and mainly rocky coast-
were constructed in Tunis with the “tuff” of Favignana, and line, marked by natural and anthropic cavities. The island is
Messina was rebuilt with it after the 1908 earthquake. After mostly flat, except for the north-south mountain ridge (M.te
the World War II the “tuff” went out of the market and the Santa Caterina, 314 m a.s.l.).
mining areas were abandoned to a degradation fate which Favignana Island mainly consists of Mesozoic-Tertiary
increased the risk of block collapse. carbonates unconformably overlain by Middle-Upper Plio-
Although the area is frequented by tourists, currently the cene marls and shales overlyed by Pleistocene biocalcaren-
quarries as well as the natural rock cliffs are undergoing ites and Tyrrhenian calcarenites (Nigro et al. 2000; Giunta
extensive erosional and landslide processes. Besides putting et al. 2002; Tavarnelli et al. 2003). The Mesozoic-Tertiary
at risk the safety of the tourists attending the area, the carbonates crop out in the western and central part of the
widespread rock falls are likely to threaten sites of great island. Lower Pleistocene biocalcarenites crop out in the
historical and anthropological value that, once destroyed, eastern part of the island (Fig. 2), generating a wide flat
can no longer be reconstructed. plateau with nearly horizontal layers. In literature, its
Geomechanical investigations and multisensor monitor- thickness ranges between 5 and 35 m (Slaczka et al. 2011),
ing have been carried out at the Cala Rossa sea cliff between though a quarry in the inner part of Cala Rossa (“Niuro
April 2012 and April 2015 with the aim of identifying the vecchio” and “Niuro nuovo” caves) shows a vertical
landslide mechanisms and defining their activity. In 2015, development of more than 80 m entirely in calcarenites.
geophysical campaigns of seismic noise measurements were The facies association suggests different depositional
carried out and the obtained results allow to associate evi- environments from the nearshore-beach zone (close to the
dences of local seismic response to zones at different sta- Mt. Santa Caterina) to the shoreface zone (in the eastern part
bility conditions, i.e. mainly related to the presence of of the Island). The Middle-Upper Pliocene marls and shale
already isolated rock blocks respect to adjacent stable zones. locally crop out between the base of the calcarenite cliffs and
Local authorities appointed to implement effective and the sea surface, partially hidden by a significant boulders
sustainable mitigation measures have to face the dual task of deposit.
allowing the enjoyment of these beautiful natural places and The calcarenite shows relatively high values of porosity
prevent accidents to the users. The definition of landslide (Regione Siciliana 2013a; Table 1) related to the low dia-
mechanisms affecting the Cala Rossa area constitutes a genetic process, the low cementation (spathic calcite with
fundamental step for the enhancement of the safe tourist meniscus structures) and to the textural characters
exploitation of the island. (equi-dimensional, well sorted, loosely packed, low fine
grained matrix). The value of the compressive strength
offered in literature, and confirmed through some field
Study Area measurements with a Schmidt hammer, indicates a weakly
cemented carbonate rock.
Favignana is the largest of the Egadi Islands, located off the There are three systems of faults that displace both the
northwest coast of Sicily (Fig. 1), near the cities of Trapani Mesozoic-Tertiary and Pleistocene deposits. A very recent
2
and Marsala. It extends for approximately 19 km and is

Fig. 1 Location of the study area Fig. 2 Bivalves in the calcareous sandstones