Location:

Period:

11 Apr 2017 08:56:33 - 14 Apr 2017 11:04:25 (3 days 2 hours 7 minutes)

Volcanoes in 100km radius:

None

Earthquakes:

8 swarms found nearby.

2007

S20070208.1(23.6km)

8 Feb

1 day 3 hours

26 earthquakes

2010

S20100110.1(29.6km)

10 Jan

3 days 20 hours

93 earthquakes

S20101206.2(25.5km)

5 Dec

1 day 1 hours

33 earthquakes

2016

S20160824.1(23.8km)

24 Aug

15 days 11 hours

415 earthquakes

S20161026.2(1.5km)

26 Oct

22 days 20 hours

1003 earthquakes

S20161031.1(5.4km)

30 Oct

8 days 14 hours

128 earthquakes

S20161128.1(1.6km)

27 Nov

5 days 11 hours

68 earthquakes

2018

S20180410.1(6.7km)

9 Apr

4 days 13 hours

68 earthquakes

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Seismic Swarm Activity in Central Italy: Insights from Event S20170412.1

Central Italy lies within the Apennine mountain chain, where ongoing extensional tectonics driven by the convergence of the African and Eurasian plates generates frequent seismic activity. The region experiences normal faulting along the Apennines, contributing to a history of moderate-to-large earthquakes. Notable events include the 2009 L’Aquila earthquake and the 2016–2017 sequence that affected areas near Amatrice and Norcia.

Between 11 and 14 April 2017, a seismic swarm designated S20170412.1 was recorded in central Italy. The sequence began at 08:56 on 11 April and concluded at 11:04 on 14 April, spanning 74 hours and 7 minutes. During this interval, 36 earthquakes were detected, with magnitudes ranging from 2.0 to 3.6 and focal depths primarily between 5 and 10 km. The largest events reached magnitude 3.6 on 11 April at 14:35 and again at 17:04, both at depths of 9–10 km. Smaller events clustered in the hours immediately following the initial shocks, illustrating the typical pattern of swarm activity where energy release occurs through numerous events rather than a single mainshock.

This swarm fits into a broader pattern observed since 2000, during which seven swarms have occurred in the region. Earlier episodes took place in 2007 (one swarm), 2010 (two swarms), and 2016 (four swarms). Such sequences often reflect fluid migration or stress redistribution along active faults without culminating in a destructive mainshock.

The shallow depths recorded during S20170412.1 are consistent with the crustal structure of the central Apennines, where brittle failure occurs within the upper 10–15 km. Monitoring by national seismic networks provides high-resolution data that help distinguish swarm behavior from typical aftershock sequences.

References

Istituto Nazionale di Geofisica e Vulcanologia (INGV). Seismic bulletins and regional tectonics summaries.
United States Geological Survey (USGS). Earthquake catalog and plate-boundary documentation for the Mediterranean region.