GNGTS 2024 - Atti del 42° Convegno Nazionale

Session 1.1 GNGTS 2024 Fig. 1 – Locatons of the 2022 and 1924 events. The later was originally located using macroseismic intensites in the Ligurian Sea, some 5 km from the coast. Instrumental data shifed the event inland, close to Bargagli. With the double aim of investgatng on the seismotectonics of the area and its geodynamic implicatons, we analysed the events occurred between 1989 and 2022. Afer relocaton using the HypoDD (Waldhauser and Ellsworth, 2000) locaton code, the events reveal a NE-SW alignment for the Savignone seismic sequence and NNW-SSE alignments for the Borzonasca and Bargagli sequences (Fig. 2). The Borzonasca seismic sequence plots in correspondence of the Villalvernia- Varzi-Otone Fault, ofen considered as the transiton between the Alps and the Apennines. The seismicity would favour the hypothesis of a kinematc actvity in comparison with the Sestri- Voltaggio Fault, along which no seismicity is currently documented. The main-shock focal solutons are invariably strike-slip, with near-vertcal NNW-SSE and NE-SW to ENE-WSW nodal planes (Fig. 2). The evident earthquake alignments in the study area mark actve, km-scale fault planes in the upper crust, pointng to a scenario of distributed strike-slip deformaton in the transiton zone between the Alps and the Apennines (Eva et al., 2023). The NE-SW faults are inherited structures that underwent major Neogene rotatons and are no longer suitably oriented to accommodate the northward moton of Adria relatve to Europe.