High-resolution analysis of the 2025 offshore seismic sequence in the Aeolian Archipelago (Southern Tyrrhenian Sea, Italy)

SUMMARY In February–March 2025 a seismic sequence occurred in the western sector of the Aeolian Archipelago (Southern Tyrrhenian Sea, Italy), a seismotectonic complex region located along the Africa-Eurasia plate boundary and mainly controlled by their NW-trending convergence. The seismicity, located ∼20 km south of Alicudi Island and ∼40 km north of the coast of Sicily, started on February 7 with an earthquake of magnitude Mw 4.7 that was followed in the next month by 42 events with local magnitudes between 1.2 and 3.4. Notwithstanding its moderate energy, this recent seismicity offers a unique opportunity to investigate seismogenic processes in a region for which a seismic potential of ∼M7 or even more has been suggested and a relevant data paucity mainly related to its offshore location was widely recognized. We tackle the limitations of not-optimal network configuration, by designing an ad-hoc approach, which integrates different advanced techniques. Specifically, we combine Bayesian methodology for accurate absolute hypocentre locations, machine learning techniques for detection of weaker events, distance geometry solvers for relative locations and a probabilistic inversion tool for source mechanism estimation. Our analysis led us to strongly enrich the data set of detected earthquakes, and to define the causative source of the 2025 sequence as a NE-SW trending N-dipping thrust faulting structure. The proposed source agrees with the regional seismogenic stress field and with the structural architecture of the southern Tyrrhenian portion of the Africa-Eurasia plate margin by also adding new constraints in a sector where no known fault segments were previously reported. This study provides new insights on seismogenic processes in the investigated area, while proving the effectiveness of the employed combined approach for characterizing seismogenic sources in poor network configurations.