GNGTS 2022 - Atti del 40° Convegno Nazionale

36 GNGTS 2022 Sessione 1.1 Fig. 1 - a) Spatial variation of Peak Delay at f c = 1.5 Hz and b) Spatial variation of Q c -1 at f c = 1.5 Hz, both for the 2016- 2017 seismic sequence. Red boxes are the fault plane activated during the AVN sequence and the black lines are the fault lines from the ITHACA catalog. Brown lines are the main thrust of the area (MST – Monti Sibillini Thrust; GST – Gran Sasso Thrust). The stars indicate the mainshocks of each 2016-2017 sequence. The main geological features are highlighted: LF - Laga Formation; UMD – Umbria-Marche Domain; LAD – Lazio-Abruzzi Domain. To further look at this variation of Q c -1 in time and space, we compared the averaged Q c -1 between 2013 and 2017 at two seismic stations located in two different sections of the seismogenic zone: GUMA, in the north, and LNSS, in the south. We observed a significant change in correspondence of the three mainshocks of Amatrice, Visso, and Norcia, with a different trend at the two stations. While at the station LNSS, southwest of Amatrice, the absorption decreases after the Amatrice earthquake, we noticed an increment at GUMA, northeast of the seismogenic zone and close to Visso, followed by a drop just after the Amatrice event and a rapid increase before Visso. At both stations, the absorption decreases after Norcia mainshock. These significant changes have a similar pattern to the temporal evolution of deep CO 2 degassing observed by Chiodini et al. (2020). The quick change in absorption between Visso and Norcia’s mainshocks is also comparable with the Vp/ Vs variation identified in the 4D velocity tomography of Chiarabba et al. (2020). Overall, the results indicate a common characteristic of the Central Apennines seismic sequences: the deep migration of fluids rich in deep CO 2 along the seismogenic area. The seismic attenuation mechanisms mapped in this work allowed us to detect the area of extension of this migration both in time and space. Acknowledgments This work has been carried out in the framework of the project Pianeta Dinamico/2020-2021 supported by Ministero dell’Istruzione, dell’Università e della Ricerca (MIUR).