GNGTS 2022 - Atti del 40° Convegno Nazionale

GNGTS 2022 Sessione 1.1 23 occurred during the 1997 Umbria-Marche sequence. Another possible reason for the scatter in the κ estimated is 3-D site effects that may generate complex site amplifications (e.g. Pitilakis, 2004; Bennington et al. , 2008). Figure 2b compares the nonparametric function of the northwest quadrant (Q1), shown with plus symbols, follows the same rate of increase with distance as the other three regions up to 100 km and for greater distances shows greater attenuation than the other three quadrants. The southern quadrants (Q3 and Q4) have similar attenuation characteristics, whereas the northern region (Q2) shows less attenuation than the other zones. In particular, the higher values of κ avg ( r ) are more evident in the southern sector, especially at the southwest quadrant (Q4 quadrant), which may be connected to a highly diffused fault a) b) Fig. 2 - a) A sample of observed kappa values (triangles) versus hypocenter distance in km from four different stations (AQU, AQV, ARRO and ARVD) and the nonparametric fit (continuous line) obtained from the inversion. b) Nonparametric Kappa functions obtained using the dataset applied in the study area. Plus symbols for group Q1, triangles for group Q2, octagons for group Q3 and diamonds for group Q4.