Seismic Swarm S20100110.1: Analysis of Central Italy Activity in January 2010

Central Italy occupies a tectonically complex zone within the Apennine mountain belt, where ongoing extension driven by the convergence of the African and Eurasian plates generates frequent seismic activity. The region features normal fault systems that accommodate crustal stretching, with earthquakes typically occurring at depths between 10 and 40 kilometers. Historical records document recurrent seismic swarms alongside larger destructive events, reflecting the area's long-term geological instability.

The swarm designated S20100110.1 was recorded in this setting, commencing at 03:12 on 10 January 2010 and concluding at 23:59 on 13 January 2010. Over 92 hours and 47 minutes, 93 earthquakes were detected. Event parameters show magnitudes ranging from 1.3 to 4.3 and focal depths predominantly clustered around 20 kilometers, with extremes of 10 and 36 kilometers.

Activity began with low-magnitude events on 10 January, including a 1.9 magnitude shock at 36 kilometers depth followed by a 2.0 magnitude event at 35 kilometers. A notable escalation occurred at 08:33 with a 4.3 magnitude earthquake at 19 kilometers depth, succeeded by several events near 3.0 magnitude within the following hours. Depths shallowed slightly during peak phases, with multiple shocks at 19–20 kilometers.

On 12 January, renewed intensification featured a 4.1 magnitude event at 25 kilometers depth and additional magnitudes of 3.7, 3.6, and 3.4, all at depths of 15–24 kilometers. The sequence maintained a pattern of clustered, moderate releases rather than isolated large ruptures. By 13 January, activity tapered, ending with events of 2.6 and 1.8 magnitude near 18–21 kilometers depth.

This swarm illustrates typical swarm behavior in the Apennines, where numerous small to moderate events occur in rapid succession without a single dominant mainshock. Depths remained consistent with regional seismicity linked to mid-crustal faulting. The episode contributed to ongoing monitoring of strain accumulation in central Italy following the 2009 L’Aquila sequence.

References

SeismoSight internal classification data for swarm S20100110.1.
Geological Survey of Italy (ISPRA) regional tectonic reports.
INGV (Istituto Nazionale di Geofisica e Vulcanologia) historical seismicity archives.