GNGTS 2016 - Atti del 35° Convegno Nazionale

GNGTS 2016 S essione A matrice 57 (approximately 32%) are undefined. Type-3 landslides were distinguished from liquefaction- related effects based on the description given in the historical chronicles, which can be retrieved in the on-line version of the catalogue. The relationships between ground effects and earthquake parameters such as seismic source energy (earthquake magnitude and epicentral intensity), local conditions (site intensity) and source-to-site distances are also analysed (Martino et al. , 2014). The analysis indicates that liquefaction, surface-faulting and ground-changes are much more dependent on the earthquake source energy (i.e., magnitude) than landslides and ground-cracks. In contrast, the latter effects are triggered at lower site intensities and greater epicentral distances than the other environmental effects. The ground effects surveyed after the Amatrice earthquake have been inventoried in the CEDIT catalogue and include 145 landslides, consisting of rock falls, rock slides, debris slides (Fig. 1). Preliminary considerations on Amatrice earthquake-triggered landslide distribution. The percentage distribution of the inventoried landslides in the involved municipalities is shown in the pie chart of Fig. 1: based on our surveys, the municipalities significantly affected by earthquake-triggered effects are Arquata del Tronto (27%), Norcia (22%), Accumoli (20%) and Amatrice (10%). In the remnant municipalities the percentage of effects respect to the total is lower than 5%. The inventoried landslides are distributed within an epicentral distance ranging from 4 km up to 41 km; this evidence is in very good agreement with the upper- bound curve by Keefer (1984), which shows that the maximum expected distance for disrupting landslides in case of M w 6.0 earthquake should be 73 km. Moreover, the maximum distance of the inventoried landslides is very close to the average distribution of distance vs. M w for Italy, as derived by Martino et al. (2014) from the CEDIT catalogue data (Fig. 2). As it regards the geographical distribution of the landslides triggered by the August 24 earthquake, they are mapped within an area 53 km long in the NW- SE direction and 27 km wide in NE-SW direction. It is worth noting the complementary spatial distribution of the landslides triggered by theAugust 24 earthquake respect to the distribution of Fig. 2 – M w vs. maximum epicentral distance: comparison of the inventoried data with the upper bound curves by Keefer (1984) and Martino et al. (2014). Fig. 3 – Distribution of the landslides inventoried after the August 24, 2016 earthquake (violet symbols) with respect to the 1997 Umbria-Marche (to the NW) and 2009 L’Aquila (to the SE) earthquakes (blue symbols).