GNGTS 2024 - Atti del 42° Convegno Nazionale

Session 1.1 GNGTS 2024 A reappraisal of the March 1952 Linera seismic sequence: the case study of the S. Tecla fault (Mt. Etna) R. Azzaro 1 , M.S. Barbano 1,2,3 , D. Musumeci 4 , G. Orefce 2 1 Isttuto Nazionale di Geofsica e Vulcanologia, Osservatorio Etneo, Catania, Italy 2 Dipartmento di Scienze Biologiche, Geologiche e Ambientali, Università di Catania, Italy 3 CRUST - Interuniversity Center for 3D Seismotectonics with Territorial Applicatons, Chiet, Italy 4 Dipartmento di Scienze Umanistche, Università di Catania, Italy Introducton The Mt. Etna region is characterised by a very frequent seismic actvity, in several cases even destructve, occurring ofen in form of seismic sequences during both eruptve periods and volcanic quiescence too (Bevilacqua et al., 2022). This volcano-tectonic seismicity has a signifcant impact partcularly in the eastern fank of the volcano where earthquakes, typically featuring very shallow focal depths (h < 3 km) and magnitude rarely exceeding M L 5, are related to the intense tectonic actvity of the Timpe fault system (Azzaro et al., 2017). The short recurrence tmes for damaging earthquakes, capable of producing macroseismic efects up to degree IX in the European macroseismic scale (hereinafer EMS, see Grünthal, 1998), gives rise to a very high level of seismic hazard in these densely urbanised area of the volcano (Azzaro et al., 2016). Long-term seismicity at Etna is very well known by the local macroseismic catalogue (hereinafer CMTE, see Azzaro and D’Amico, 2014) which parametrises, startng from a general revision of the historical sources documentng past earthquakes (Azzaro et al., 2000), also fore- and afer-shocks and provides indicaton on the causatve faults. This makes it possible to reconstruct the seismic history of each seismogenic structure (Azzaro et al, 2013). In this framework, the S. Tecla fault shows a high seismic potental (Fig. 1a), with a number of strong and minor events rupturing diferent segments of the structure (Azzaro et al, 2017). The strongest known earthquake is the 1914 event, which entrely ruptured along strike destroying the locality of Linera and surroundings; the maximum intensity was assessed to reach degree IX-X EMS and the equivalent magnitude estmated as M L 5.2. An event with similar features is the 19 March 1952 earthquake (Fig. 1b), that almost destroyed again Linera along the central sector of the S. Tecla fault and was preceded by a seismic sequence afectng the northern segment of the fault, south to the town of Zaferana Etnea. The mainshock is reported in the CMTE catalogue according to the intensity dataset by Patanè and Imposa (1995), the only one available, and was not revised in the phase of the catalogue compilaton since this study was recent. The maximum intensity was assessed as VII-VIII EMS, corresponding to an equivalent magnitude of M L 4.0.