Location:

Period:

19 Oct 2010 12:39:59 - 26 Oct 2010 07:25:08 (6 days 18 hours 45 minutes)

Volcanoes in 100km radius:

Colli Albani(95km)

Earthquakes:

375

16 swarms found nearby.

2007

S20070208.1(29.0km)

8 Feb

1 day 3 hours

26 earthquakes

2009

S20090510.1(19.4km)

9 May

13 days 16 hours

178 earthquakes

S20090626.1(11.2km)

25 Jun

3 days 7 hours

118 earthquakes

S20090713.1(10.5km)

12 Jul

6 days 5 hours

128 earthquakes

S20090801.1(27.5km)

31 Jul

19 days 15 hours

224 earthquakes

S20090823.1(8.8km)

22 Aug

6 days 9 hours

83 earthquakes

2010

S20100831.1(8.9km)

30 Aug

25 days 22 hours

427 earthquakes

S20101001.1(10.4km)

30 Sep

11 days 3 hours

111 earthquakes

S20101104.1(7.7km)

3 Nov

6 days 0 hours

176 earthquakes

S20101206.2(26.0km)

5 Dec

1 day 1 hours

33 earthquakes

2011

S20110215.1(28.4km)

15 Feb

1 day 8 hours

27 earthquakes

S20110306.1(10.9km)

5 Mar

8 days 1 hours

87 earthquakes

S20111019.2(1.8km)

18 Oct

1 day 4 hours

25 earthquakes

2016

S20160824.1(29.9km)

24 Aug

15 days 11 hours

415 earthquakes

S20161030.1(21.3km)

30 Oct

3 days 20 hours

72 earthquakes

2017

S20170118.1(15.4km)

18 Jan

5 days 9 hours

231 earthquakes

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Seismic Swarm S20101020.1 in Central Italy: October 2010 Analysis

Central Italy occupies a tectonically active segment of the Apennine chain, where ongoing extensional faulting along northwest-southeast trending normal faults accommodates regional extension at rates of several millimeters per year. This setting produces frequent low-to-moderate seismicity, often clustered in swarms rather than classic mainshock-aftershock sequences. The October 2010 swarm occurred within this framework, consistent with the area's long-term behavior documented through instrumental monitoring.

Swarm S20101020.1 began at 12:39 on 19 October 2010 and concluded at 07:25 on 26 October 2010, spanning 162 hours and 45 minutes. During this interval, 375 earthquakes were recorded. Examination of the first 100 events reveals a classic swarm pattern: rapid onset, absence of a dominant mainshock, and sustained activity with fluctuating magnitudes. Depths remained shallow, predominantly between 5 km and 11 km, indicating rupture within the brittle upper crust. Magnitudes ranged from 1.0 to 3.7, with the peak event (M 3.7) occurring at only 2 km depth on 20 October at 10:23. Other notable events included an M 3.4 at 10 km depth shortly after 06:47 on the same day and several events exceeding M 2.5 clustered around 08:00–09:00.

Temporal distribution shows the highest rate in the first 36 hours, followed by a gradual decline punctuated by small bursts. Most events clustered near 9–11 km, though occasional shallower foci (4–6 km) appeared, possibly reflecting minor upward migration along fault planes. No events in this initial cohort exceeded M 4.0, underscoring the swarm's diffuse energy release.

Since 1 January 2000, eight swarms have been documented in the same sector of Central Italy. Prior episodes occurred in 2007 (one swarm), 2009 (five swarms), and earlier in 2010 (two swarms). This recurrence highlights the region's propensity for swarm-type sequences, likely driven by fluid migration or slow slip transients along segmented normal faults.

Collectively, the 2010 swarm reinforces the characteristic seismic style of Central Italy: prolonged, low-magnitude activity distributed across shallow crustal volumes without immediate escalation to damaging events.

References

SeismoSight internal swarm catalogue S20101020.1
Istituto Nazionale di Geofisica e Vulcanologia (INGV) seismic bulletins
European-Mediterranean Seismological Centre (EMSC) regional records