The SISMIKO Monitoring Network and Insights into the 2024 Seismic Swarms on the Ionian Side of the Calabrian Arc

Following the Mw 5.0 earthquake of 1 August 2024, which struck the Ionian sector of north-central Calabria (southern Italy), the SISMIKO emergency group of INGV deployed a temporary seismic network to enhance coverage of the National Seismic Network. This improved configuration enabled the relocation of over 1300 aftershocks and the identification of a second swarm near Cirò, active since May and reactivated after mid-August. A machine learning workflow was applied for automatic phase picking, event association, and relocation, producing a high-resolution catalogue. The seismicity of both sequences aligns with the NW-trending Rossano–San Nicola shear zone but reveals distinct rupture patterns: the Pietrapaola sequence, targeted by the SISMIKO deployment, shows compact hypocentral clustering, while the Cirò swarm displays more scattered seismicity. The analysis of the catalogue reveals a two-slope temporal decay of aftershocks and relatively low completeness magnitudes. Source geometry inferred from hypocentre distributions and INGV focal mechanisms supports the structural interpretation. Overall, the machine learning-based catalogue proved effective for near-real-time analysis and offers new insights into the active tectonic framework of the Calabrian Arc.