Abstract

The fourth, and last, quadrangle of the study area presents 81 eathquake-triggered landslides, 38 of which are uncertain, plus 1 certain and 7 uncertain cases of river blockage. As in the previously examined quadrangles, landslides present: (1) conspicuous size, (2) old age, (3) dormant state, (4) gentle slope-angle, and (5) typology suitable for reactivation. In case of reactivation are at risk, among others: the town of Buccheri, several residential or rural settlemets and several important lines of communication. Considering the entire area (i.e. the 1:100 000 quadrangles nr. 273, 274, 276 and 277 of the Carta Topografica d'Italia by the Italian Istituto Geografico Militare), 146 landslides were found, 64 of which uncertain (Nicoletti et alii, 1999a, b; Nicoletti & Catalano, 2000). In nearly all cases only one type of movement is represented, with a 90% of "slides". In most cases the landslide material is lithified rock. Slip surfaces are most frequently circular in section, with low curvature; listric surfaces are also common while planar surfaces are rare. These surfaces are normally gently inclined, and slope between only 10 degrees and 20 degrees in more than 50% of cases. A relationship with the earthquake of 1693 is certain in 1 case, and uncertain in 5 cases. In addition, a relationship between 3 landslides and the 1169 earthquake is suspected. Eight certain, and 12 uncertain, landslide dams were also identified. Landslide reactivation is possible nearly everywhere and can cause serious damage in many sites: in particular are at risk 4 towns, 96 minor residential or rural settlements, 9 segments of state roads, 19 segments of important roads and 6 segments of railways.

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