GNGTS 2022 - Atti del 40° Convegno Nazionale

GNGTS 2022 Sessione 2.2 327 source-to-site path. These are related to anomalies in crustal velocity, density or in the attenuation function. • A map of the site effects based on the spatial correlation of the site-to-site residual terms (δS2S). These are calculated with respect to the average ground motion level at the reference sites, so they can be considered as a proxy of the amplification function of the site; The method provides more accurate predictions with respect to standard GMM applied in Italy along with less total uncertainty (Sgobba et al. , 2021). Fig. 1 - Sketch of Sgobba et al. (2021) method for the generating empirical shaking scenarios at the site. Findings and developments. The approach has been applied to past events, as well as for predictive purposes of virtual events, leading to build a portfolio of scenarios for Central Italy that include the main events occurred in the area in the last years, such as L’Aquila Mw6.0 2009, Amatrice Mw6.1 2016, Norcia Mw6.5 2016 or historical events like Gubbio Mw 5.6 1984 and Fucino Mw6.7 1915 (example of map in Fig. 2). The application of the method to the reconstruction of historical events in the pre- instrumental era is strategic, as it allows new insights to be gained into the study of such events thanks to the exploitation of the extensive sampling of records available in this region to date. The obtained spatially-variable fields reproduce anisotropy and non-stationarity of the main ground motion patterns related to physical features not captured by ergodic GMMs, such as systematic effects linked to the seismic source and the crustal propagation that are documented in the literature for the selected events with reference to instrumental data or macroseismic observations. Fig. 2 - Example of shaking map of the historical earthquake Mw6.7 1915 Fucino (median field) (a) and variability map (b) for PGA. Star indicates the epicenter of the event, black triangles indicate the observing sites, the rectangle represents the fault rupture projection. (a) (b)