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Note:This page contains AI-generated content for informational and entertainment purposes only. It may contain inaccuracies. Raw event data is from USGS and EMSC. All statistics, lists, and derived information are generated by this site. Full disclaimerFound an error?
Location:
CENTRAL ITALY
Period:
22 Aug 2009 09:41:45 - 28 Aug 2009 19:20:55 (6 days 9 hours 39 minutes)
Volcanoes in 100km radius:
Colli Albani(99km)
Earthquakes:
83
17 swarms found nearby.
2007
S20070208.1(26.7km)
8 Feb
1 day 3 hours
26 earthquakes
2009
S20090330.1(28.5km)
30 Mar
98 days 16 hours
6163 earthquakes
S20090510.1(12.1km)
9 May
13 days 16 hours
178 earthquakes
25 Jun
3 days 7 hours
118 earthquakes
12 Jul
6 days 5 hours
128 earthquakes
S20090801.1(20.1km)
31 Jul
19 days 15 hours
224 earthquakes
2010
30 Aug
25 days 22 hours
427 earthquakes
30 Sep
11 days 3 hours
111 earthquakes
19 Oct
6 days 18 hours
375 earthquakes
3 Nov
6 days 0 hours
176 earthquakes
S20101206.2(29.1km)
5 Dec
1 day 1 hours
33 earthquakes
2011
S20110215.1(23.1km)
15 Feb
1 day 8 hours
27 earthquakes
5 Mar
8 days 1 hours
87 earthquakes
18 Oct
1 day 4 hours
25 earthquakes
2016
S20160824.1(27.2km)
24 Aug
15 days 11 hours
415 earthquakes
S20161030.1(15.0km)
30 Oct
3 days 20 hours
72 earthquakes
2017
18 Jan
5 days 9 hours
231 earthquakes
AI-generated article — for informational and entertainment purposes only. May contain inaccuracies. Full disclaimerFound an error?

Seismic Swarm S20090823.1 in Central Italy

Central Italy lies within the Apennine mountain chain, a region shaped by ongoing tectonic interactions between the Eurasian and African plates. The area features active normal faulting driven by extensional stresses, resulting in frequent low-to-moderate magnitude seismicity. Crustal depths typically range from 5 to 15 km for such events, consistent with the brittle upper crust in this extensional regime.

Seismic swarms are a recognized phenomenon in the Apennines, often linked to fluid migration along faults or stress redistribution without a single dominant mainshock. Historical records indicate recurrent swarm activity, with documented episodes contributing to the region's seismic hazard profile. Major historical earthquakes, such as those in 1997 and 2009, underscore the potential for larger events amid background swarm occurrences.

The S20090823.1 swarm, classified internally by SeismoSight, began at 09:41 on 22 August 2009 and concluded at 19:20 on 28 August 2009. Over 153 hours and 39 minutes, 83 earthquakes were recorded in central Italy. Magnitudes ranged from 1.4 to 3.6, with the largest event occurring at 23:18 on 26 August at a depth of 5 km. Depths predominantly clustered between 5 and 13 km, reflecting typical nucleation levels for Apennine crustal faults.

Event distribution showed temporal clustering, with elevated activity on 22–24 August and a notable peak on 26 August. Multiple events exceeded magnitude 2.5, including those at 3.5 (20:20 on 22 August, 5 km depth), 3.3 (03:05 on 23 August, 5 km depth), 2.8 (16:47 on 22 August, 8 km depth), and additional 2.8 events on 24 and 26 August. Shallower foci (2–5 km) appeared intermittently, while most remained around 10–11 km.

This pattern aligns with regional swarm characteristics observed since 2000, during which six swarms have occurred. Prior episodes include one in 2007 and five in 2009, highlighting elevated swarm frequency that year. Depths and magnitudes in S20090823.1 fall within established ranges for central Italian seismicity, supporting ongoing monitoring of fluid-influenced fault systems.

References

  • Istituto Nazionale di Geofisica e Vulcanologia (INGV) seismic catalogs
  • United States Geological Survey (USGS) earthquake data archives
  • SeismoSight internal swarm classification records