Geological control on large seismically induced landslides: the case of Cerda (Southern Italy)

摘要

On September 6th, 2002, a large landslide was triggered by an Ml = 5.6 earthquake in the country area of Cerda (Sicily - Italy). The main shock epicentre was located offshore in the Tyrrhenian sea, about 40 km far from Palermo city and close to the Aeolian Islands. The studied landslide involved an area of about 1.5 km2, along the left bank of the Imera River and caused significant damage to farmhouses, roads and aqueduct. Based on the survey of the ground cracking pattern, morphological features and damage location this coseismic slope failure has been defined as an earthslide; the inferred depth of the slip dip surface is between 10 and 50m b.g.l. and the volume of the displaced mass results in the range of some tens of million of cubic meters. Electric and seismic surveys provided further information on the geological and structural setting of the landslide area. A tear fault was identified between marls and the scaly clay affected by the landslide process. Geophysical methods highlighted also a diffuse heterogeneity in the electric and elastic properties of the scaly clays in the landslide mass as well as their relative low conductivity that can be reasonably referred to the absence of groundwater. Grants: CNR-GNDCI 03.00060.GN42 Responsible Prof. A. Prestininzi.