Location:

Period:

5 Dec 2010 19:41:20 - 6 Dec 2010 20:47:25 (1 day 1 hour 6 minutes)

Volcanoes in 100km radius:

None

Earthquakes:

11 swarms found nearby.

2007

S20070208.1(17.1km)

8 Feb

1 day 3 hours

26 earthquakes

2009

S20090823.1(29.1km)

22 Aug

6 days 9 hours

83 earthquakes

2010

S20101020.1(26.0km)

19 Oct

6 days 18 hours

375 earthquakes

2011

S20111019.2(27.6km)

18 Oct

1 day 4 hours

25 earthquakes

2016

S20160824.1(18.5km)

24 Aug

15 days 11 hours

415 earthquakes

S20161026.2(24.0km)

26 Oct

22 days 20 hours

1003 earthquakes

S20161030.1(26.4km)

30 Oct

3 days 20 hours

72 earthquakes

S20161031.1(23.2km)

30 Oct

8 days 14 hours

128 earthquakes

S20161128.1(25.3km)

27 Nov

5 days 11 hours

68 earthquakes

2017

S20170412.1(25.5km)

11 Apr

3 days 2 hours

36 earthquakes

2018

S20180410.1(29.3km)

9 Apr

4 days 13 hours

68 earthquakes

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Seismic Swarm in Central Italy: December 2010

Central Italy lies within the Apennine mountain chain, where ongoing extensional tectonics driven by the rollback of the Adriatic slab produces frequent seismic activity. The region experiences normal faulting along northwest-southeast trending structures, with earthquakes typically occurring at shallow to mid-crustal depths between 5 and 20 km. Historical records document destructive events such as the 1703 Norcia and 1915 Avezzano earthquakes, while modern monitoring has recorded sequences including the 1997 Umbria-Marche and 2009 L’Aquila events. These reflect the persistent strain accumulation along the chain.

SeismoSight recorded swarm S20101206.2 in this tectonic setting. The sequence began at 19:41 on 5 December 2010 and concluded at 20:47 on 6 December 2010, lasting 25 hours and 6 minutes. During this interval, 33 earthquakes were detected. Magnitudes ranged from 1.4 to 4.0, with the majority of events clustered between 7 and 11 km depth and two events located at 20 km. The largest shock, magnitude 4.0, occurred at 10:32 on 6 December at 20 km depth. Earlier activity included a magnitude 3.1 event at 20:54 on 5 December, also at 20 km. Most remaining events remained below magnitude 2.0 and were distributed across depths of 6–11 km, indicating a compact source volume consistent with swarm behavior rather than a single mainshock-aftershock sequence.

This swarm represents the third such episode documented by SeismoSight since 1 January 2000. Earlier swarms occurred in 2007 (one event) and 2009 (one event), underscoring the episodic nature of low-to-moderate clustered seismicity in the area. Such swarms typically arise from fluid migration or aseismic slip along favorably oriented faults within the extending Apennine crust and rarely produce surface rupture.

The 2010 swarm did not escalate into a larger mainshock and remained within the background range of regional microseismicity. Continued monitoring by national networks provides essential data for refining fault models and assessing long-term hazard along the central Apennines.

References
Istituto Nazionale di Geofisica e Vulcanologia (INGV) seismic bulletins
SeismoSight internal swarm classification records