GNGTS 2024 - Atti del 42° Convegno Nazionale

Session 1.1 GNGTS 2024 maximum amplitudes and, consequently, the magnitude automatcally. Through this analysis, they have identfed an earthquake with a magnitude of M L =3.4, occurring approximately one minute afer the mainshock and overlooked during the surveillance service. Furthermore, a comprehensive efort to recover smaller seismic events not initally analyzed in the Seismic Monitoring Room resulted in the localizaton of 498 earthquakes, nearly a 30% increase within the frst three days. In Figure 1(a-d), hypocentral parameters and tme readings of the 352 earthquakes detected in the Seismic Monitoring Room have been compared with those of the same events revised by the BSI. It is evident as both the horizontal and vertcal errors, as well the seismic gap associated with the locaton decrease for the dataset analyzed from the BSI, while the number of P and S phases increases for the same dataset. Subsequently, the events revised from BSI were initally relocated by applying the NonLinLoc code (Lomax et al., 2000) using a 1D regional velocity model from Pastori et al. (2019). Following this, a double-diference technique (Waldhauser and Schaf, 2008) was applied to improve the geometries of the actvated structures (see Figure 2). Fig.1 – Comparison between hypocentral parameters (a,b,c) and used tme readings (d) for the same 352 earthquakes detected, during the frst 3 days of the sequence, from seismic monitoring room and revised from BSI. Concomitantly, an analysis using the template-matching technique was applied, for the period from September frst to October 10th, to identfy events overlooked by the Earthworm system in the Seismic Monitoring Room. The results are shown in Figure 3. It was found that the number of detectons increased by approximately 60%. Furthermore, Figures 3c and 3d put in evidence as the