GNGTS 2024 - Atti del 42° Convegno Nazionale

Session 2.2 GNGTS 2024 esCmate of seismic shaking expected at a site. This depends on the locaCon of the surrounding seismogenic zones, whose seismicity rate can be inferred from historical and instrumental records. Then, ground moCon predicCon equaCons (GMPE) are used to esCmate the probability of a site to experience seismic shaking of different levels on a flat surface with outcropping sCff lithology. These site condiCons, however, differ from those of slopes suscepCble to seismically induced landslides, where the slope response to seismic waves can considerably aggravate the destabilizing effects of shakings. A method for a probabilisCc evaluaCon of the resistance demand was proposed by Del Gaudio et al. (2003) through the quanCty (A c ) x , which represents the criCcal acceleraCon A c that a slope must have to keep the probability of landslide triggering, for expected earthquakes, within a pre-defined probability level (e.g., 10% in 50 years). The condiCon of landslide triggering is idenCfied by the exceedance of a criCcal threshold x of the permanent displacement induced by seismic shaking, measured, according to the Newmark (1965) model, as Newmark displacement D N . The calculaCon of (A c ) x is based on an empirical relaCon calibrated by Romeo (2000), in which D N is expressed as a funcCon of the Arias Intensity (Arias, 1970) (which measures the ground shaking) and of the slope criCcal acceleraCon a c (which measures the slope resistance to failure). In their first applicaCon of the proposed method Del Gaudio et al. (2003), produced a map of slope resistance demand in terms of (A c ) x values for the area of Daunia Mts. (Fig. 1 a). They exploited the following data and tools available at that Cme: the ZS4 seismogenic zonaCon (Scandone, 1997), a GMPE for Arias Intensity published by Sabeba and Pugliese (1996) and the SEISRISK III sopware (Bender and Perkins, 1987) to calculate the seismic shaking probabiliCes. The map shows the results in terms of criCcal acceleraCon that slopes must have to keep within 10% in 50 years the probability that D N exceed 10 cm. Site amplificaCon effects were not considered. Fig. 1: Basic resistance demand maps calculated for the Daunia area, expressed through the quanCty (A c ) 10 : (a) results obtained by Del Gaudio et al. (2003); (b) new version of the same map obtained using updated versions of the seismogenic zonaCon and of the earthquake catalogue.