GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 1.2 GNGTS 2023 The sustained shallow low-energy seismicity (0.5-1 km) between Solfatara and Pisciarelli in both periods is remarkable, most notable during the current unrest: the shallowing of fractures may be related to the reactivation of previously sealed faults that could re-open after crustal deformation due to overpressure (Kilburn et al., submitted). In both periods of unrest, we note the persistence of seismicity along a nearly horizontal alignment at a depth of 1-1.5 km SW of the Solfatara, extending to the coastline, which indicates a high-strength horizon where a large amount of the radiated seismic energy accumulates. This horizon could be the seismic signature of the low permeability caprock placed at depth less than 1.5 km (Vanorio and Kanitpanyacharoen, 2015; Kilburn et al., submitted) which acts as a structural barrier to fluid migration. Offshore seismicity is present in both unrest periods, more intense during the years 1982-84, generally aligned along a well-known border structure of the inner CFc (Di Luccio et al., 2015), NW-SE oriented and dipping towards SW (Castaldo et al. 2019; Natale et al., 2022). Figure 1 A) Relative locations of earthquakes in the CFc for 1982-1984 unrest (top) and vertical section along the profile XX’ (bottom). Size of circles is proportional to magnitude, color code follows the legend. The catalog is cut for the magnitude of completeness Mc=0.5. The grey star indicates the position corresponding to Solfatara. B) Same as A) but for 2005-2022. Magnitude of completeness is Mc=0.2. References Bianco F., Caliro S., Martino P. D., Orazi M., Ricco C., Vilardo G., et al.; 2022: Campi Flegrei, A Restless Caldera in a Densely Populated Area. Active Volcanoes World, 219–237. doi:10.1007/978-3-642-37060-1_8.