Gis-based permanent displacement maps for urban planning of unstable seismic territories: a case study in Daunia Apennine (Apulia, Italy)

Abstract

Earthquake induced landslides (EIL) represent coseismic effects that heavily affect seismic territories worldwide and must be taken into account in urban planning according to national laws and technical provisions. Inventories of earthquake-triggered landslides and and geotechnical characterization of soils involved into mass movements are commonly prescribed to predict EIL with increasing details as the scale of the study increases. EIL hazard is assessed through several different methods. At urban scale, the deterministic approach of the Newmark’s sliding rigid block method is commonly employed to draw EIL hazard maps by calculating permanent displacements triggered by seismic events. Thematic maps built within ArcGis environment have been combined to draw hazard maps through the raster calculator tool (ARCMAPTM 2010). In this paper the Newmark’s method is applied to the case study of Deliceto town, located in Daunia Apennine (Apulia, Southern Italy). This territory is characterized by frequent and widespread landslide phenomena triggered by seasonal rainfalls and strong earthquakes, such as the 23rd November 1980 Irpinia earthquake. In particular, Deliceto is affected by the highest seismic level within Daunia territory corresponding to the expected peak ground acceleration (PGA) equal to 0.20 g. The outcomes of the present study suggest that the highest permanent displacements are expected along steep slopes made up of an alternation of limestones and marly clays belonging to the Flysch Faeto Fm.