GNGTS 2022 - Atti del 40° Convegno Nazionale

GNGTS 2022 Sessione 2.1 199 3.2 Propagation effects . In order to perform a zonation of ground motion attenuation, we assume that the event- and site- corrected residuals are totally justified by a regional deficit of anelastic attenuation, not explained by the model, named δc 3 . The latter represents the correction of the anelastic attenuation coefficient c 3 of ITA18 that compensates the δW es residuals record by record. For the purpose of studying the spatial variability of propagation effects, we assign δc 3 to the midpoint along the event-to-station path, as representative of the area affected by the wave propagation. Moreover, we consider only the recordings with source-to-site distances above 80km, because the effects of the anelastic attenuations become relevant for long event-station distances. As a reference zonation for attenuation, we adopt the model developed by Basili et al. (2019) in the framework of TSUMAPS-NEAMproject, aiming at developing the first probabilistic earthquake-induced tsunami hazard assessment (Seismic PTHA, S-PTHA) for the coasts of the northeast Atlantic ocean, the Mediterranean sea, and related seas (NEAM). The final proposal (Figure 2) to introduce local propagation effects into GMMs is a further simplification of TSUMAPS zonation, considering the short period δc 3 spatial trend. Some zones show significantly positive δc 3 , such as North-western Alps (zone 1 in Figure 2) and Hyblean Plateau (zone 17). An increase in the attenuation is visible from the Adriatic coast (zones 8 and 11 Fig. 2 - Zonation for regionalization of attenuation effects into GMMs.