Location:

Period:

30 Oct 2016 09:02:29 - 7 Nov 2016 23:20:59 (8 days 14 hours 18 minutes)

Volcanoes in 100km radius:

None

Earthquakes:

128

8 swarms found nearby.

2007

S20070208.1(18.6km)

8 Feb

1 day 3 hours

26 earthquakes

2010

S20100110.1(28.7km)

10 Jan

3 days 20 hours

93 earthquakes

S20101206.2(23.2km)

5 Dec

1 day 1 hours

33 earthquakes

2016

S20160824.1(18.6km)

24 Aug

15 days 11 hours

415 earthquakes

S20161026.2(4.6km)

26 Oct

22 days 20 hours

1003 earthquakes

S20161128.1(4.0km)

27 Nov

5 days 11 hours

68 earthquakes

2017

S20170412.1(5.4km)

11 Apr

3 days 2 hours

36 earthquakes

2018

S20180410.1(12.1km)

9 Apr

4 days 13 hours

68 earthquakes

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Seismic Swarm S20161031.1: Insights from Central Italy's October-November 2016 Activity

Central Italy lies within the Apennine mountain belt, where ongoing extensional tectonics driven by the rollback of the Adriatic slab produces frequent shallow crustal earthquakes. The region features active normal faults oriented northwest-southeast, with typical focal depths between 5 and 15 km. Historical records document repeated seismic episodes, including destructive events in 1997, 2009, and the 2016 sequence, underscoring the area's persistent seismic hazard.

Swarm S20161031.1 began at 09:02 on 30 October 2016 and concluded at 23:20 on 7 November 2016, spanning 206 hours and 18 minutes. During this interval, 128 earthquakes were recorded across central Italy. Analysis of the first 100 events reveals predominantly low-to-moderate magnitudes, with values ranging from 2.3 to 4.3. The largest event, magnitude 4.3, occurred on 2 November at 19:37:49 at a depth of 8 km. Most events clustered between 2.5 and 3.5, indicating a typical swarm pattern without a single dominant mainshock.

Depth distribution remained shallow, averaging near 9 km and rarely exceeding 13 km. This concentration points to brittle failure within the upper crust, consistent with the extensional regime of the Apennines. Temporal patterns show elevated activity on 30 October and 2 November, with multiple events occurring within minutes on several occasions, such as the pair at 13:21 and 13:23 on 30 October.

The sequence fits into a broader historical context. Since 1 January 2000, five swarms have been documented in the region, occurring in 2007 (one swarm), 2010 (two swarms), and 2016 (two swarms). These episodes highlight recurring clustered seismicity along the same fault systems.

Overall, the swarm exhibited classic features of Apenninic seismic activity: shallow depths, moderate magnitudes, and episodic bursts. Such events contribute to ongoing strain release without producing widespread surface rupture.

References

SeismoSight internal classification records for swarm S20161031.1
Regional geological framework from Apennine tectonics studies (INGV and peer-reviewed literature up to 2023)