Seismic swarm S20181224.1 was recorded in Sicily, Italy, beginning at 18:50 on 23 December 2018 and concluding at 21:14 on 28 December 2018. Over this 122-hour 24-minute interval, a total of 91 earthquakes were registered. The sequence featured predominantly shallow events, with depths ranging from 0 to 10 km and magnitudes between 2.0 and 5.0. Notable activity included multiple events exceeding magnitude 3.0 on 24 December, culminating in a magnitude 4.3 quake at 16:50, followed by a magnitude 5.0 event at 02:19 on 26 December.
The swarm exhibited typical characteristics of clustered seismicity, with the majority of events occurring within the first 48 hours and a gradual decline thereafter. Depths remained consistently shallow, indicating activity within the upper crust. This pattern aligns with tectonic stress release along regional fault systems rather than isolated mainshock-aftershock sequences.
Sicily occupies a complex tectonic setting at the convergent boundary between the African and Eurasian plates. The island forms part of the central Mediterranean, where ongoing collision and subduction processes drive seismic and volcanic activity. Eastern Sicily, in particular, lies near the Ionian subduction zone and the Malta escarpment, contributing to frequent low-to-moderate magnitude earthquakes. Mount Etna, Europe's most active volcano, dominates the regional geology and is influenced by both tectonic extension and magma movement.
Historical records indicate limited swarm occurrences in the area since 2000, with only two prior episodes documented in 2002 and 2011. These events underscore the episodic nature of clustered seismicity in Sicily, often linked to the broader plate-boundary dynamics that have produced significant historical earthquakes, including the destructive 1908 Messina event.