Mechanisms Of Slope Failure During StrongGround Motion In Southern Italy - SomeHistorical Evidence

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A review of the contemporary and current literature on moderate to large historical earthquakes in southern Italy (Calabria and Sicily) have allowed the mapping of slope failures associated with seismic events. Descriptions from Hamilton, Lyell, Barratta and Cotecchia form the basis of the location of many of these slides. Aerial photography and satellite imagery have assisted in the location of many landslides. The wide range of values of peak horizontal ground acceleration at which landslides have occurred suggests that this parameter, and subsequently distance and magnitude, are poor predictors of the potential of seismic events to produce landslides. Additionally reports of large coseismic movements of groundwater have been associated with a number of earthquakes in Calabria and are likely to have been influential in causing slope failure. This is one additional ground condition which cannot be modelled in terms of earthquake magnitude. Three broad categories of seismically-triggered landslides can be identified. The first refers to landslides due to excess pore water pressures similar to the mechanism proposed by Youd & Keefer [1]; the second refers to tensional failure in rock masses; the third relates to the presence of topographic irregularities, and preexisting discontinuities, which may act in such a way as to amplify differences in shaking on either side of the surface in question. The morphological differences in the slopes which showed failure suggests that topographic differences may be a vital component on determining slope failure.