GNGTS 2016 - Atti del 35° Convegno Nazionale

56 GNGTS 2016 S essione A matrice In case of reactivation of translational or roto-translational slides the following evidence has been collected: - ground cracks cutting paths, roads or soil and involving fresh vegetation; - debris accumulation at the landslide toe over roads or paths. To check the reliability of the above listed evidence, after having checked the national landslide inventory (IFFI Project, ISPRA), the most recent satellite images available on-line were compared to pictures taken during the field surveys to verify that the inventoried effects were not existing before. Inventorying. The CERI’s Italian Catalogue of Earthquake-Induced Ground Failures (CEDIT) stores data about ground failures induced by earthquakes with an epicentral intensity of at least 8 on the MCS scale, which occurred from 1000 AD. The bibliographic sources available for historical earthquakes are reported and cited in the catalogue. On-line reporting (possible by a web-site mail) were also taken into account. Several recent seismic events in Italy that have produced relevant ground effects (e.g., 1976 Friuli M w 6.4, 1980 Irpinia M w 6.9, 1997 Umbria-Marche M w 6.0, 2009 L’Aquila M w 6.2, 2012 Emilia M w 6.0), proved that earthquake-induced ground effects can lead to a risk level comparable to the earthquake shaking itself. The CEDIT database is published online for public access at the URL http://www.ceri . uniroma1.it/index.php/web-gis/cedit/ and hosted on the web server of the Research Centre for the Geological Risks (CERI) of the Sapienza University of Rome (Fortunato et al. , 2012). The WebGIS system has been developed by using the Flex interface of ArcGIS (ESRI™) server technology. The system provides a geo-database consulting and querying interface with graph or table outputs. The CEDIT database reports approximately 2000 localities where ground failures were triggered by 166 earthquakes that occurred in the last millennium in Italy for which information about the occurrence of ground effects can be retrieved from historical documents. The ground effects collected in the database fall into five main categories: landslides, ground-cracks, liquefaction, surface-faulting and ground-changes (these last ones including among others: subsidence, relevant morphological changes due to river damming, lake formation and so on). These categories are further divided into sub-categories, specifying the type of effect, such as, for example, the landslide kinematic type. Summary statistics of the database content (Martino et al. , 2014) indicate that 14% of the italian municipalities have experienced at least one earthquake-induced ground effect and that landslides are the most common (approximately 45%), followed by ground-cracks (32%) and liquefaction (18%). Among landslides, approximately 40% can be ascribed to Keefer’s (1984, 2002) type-1 category of landslides triggered by earthquakes (falls and disrupted slides), 22% to type-2 (coherent slides), 6% to type-3 (lateral spreads and flows) and a considerable number Fig. 1 – Examples of surveyed landslides, triggered by the August 24, 2016 earthquake and distribution of earthquake- induced landslides in the municipalities struck by the August 24, 2016 earthquake.