Location:

Period:

4 May 2022 03:45:57 - 5 May 2022 09:16:55 (1 day 5 hours 30 minutes)

Volcanoes in 100km radius:

None

Earthquakes:

8 swarms found nearby.

2007

PS20070329.1(71.2km)

29 Mar

3 hours

6 earthquakes

2008

PS20081219.1(36.0km)

18 Dec

1 day 14 hours

8 earthquakes

2010

PS20100308.2(47.5km)

8 Mar

6 hours

6 earthquakes

2011

PS20110317.2(38.9km)

16 Mar

16 hours

5 earthquakes

2015

PS20150916.2(100.6km)

16 Sep

1 day 14 hours

48 earthquakes

PS20150917.2(35.4km)

17 Sep

21 hours

9 earthquakes

PS20150921.1(92.1km)

21 Sep

1 day 1 hours

7 earthquakes

2017

PS20170428.1(113.0km)

28 Apr

2 hours

6 earthquakes

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Seismic Swarm S20220504.1: Analysis of Activity Near La Ligua, Chile

Seismic swarm S20220504.1 occurred 61 km west-northwest of La Ligua in Chile's Valparaíso Region. The sequence began at 03:45 on 4 May 2022 and concluded at 09:16 on 5 May 2022, spanning 29 hours and 30 minutes. During this period, 42 earthquakes were recorded, with magnitudes ranging from 2.5 to 5.2 and focal depths between 9 km and 44 km.

The swarm featured several notable events. The initial shock reached magnitude 4.9 at 11 km depth. Subsequent activity included a magnitude 4.8 event at 17 km depth and a peak magnitude 5.2 earthquake at 20 km depth on 4 May at 11:59:34. Additional events of magnitude 4.4 at 10 km depth and multiple magnitude 3+ shocks occurred throughout the sequence, with the majority clustered between 15 km and 35 km depth. Activity tapered off with smaller events on 5 May, ending with a magnitude 2.8 shock at 30 km depth.

This swarm reflects typical patterns in subduction-related seismicity. The region lies above the convergent boundary where the Nazca Plate subducts beneath the South American Plate at rates of approximately 6–7 cm per year. Such settings generate both megathrust earthquakes and shallower crustal swarms due to stress transfer along the plate interface and overlying faults. Depths recorded in the swarm align with the seismogenic zone in central Chile, where intermediate-depth activity often occurs within the overriding plate or near the slab interface.

Central Chile maintains one of the highest seismic hazard levels globally owing to its position in the Pacific Ring of Fire. Historical records document repeated large earthquakes, including the 1730 event estimated at magnitude 9.0–9.5 and the 2010 Maule earthquake of magnitude 8.8, both of which produced significant shaking in the Valparaíso area. These great events release accumulated strain but can also trigger aftershock sequences and swarms in adjacent segments.

Since 2000, eight seismic swarms have been documented in the broader region, occurring in 2007, 2008, 2010, 2011, 2015 (three separate episodes), and 2017. These episodes demonstrate recurring episodic release of stress without progression to a major mainshock, consistent with the area's tectonic regime of frequent moderate activity punctuated by infrequent great earthquakes.

The S20220504.1 swarm provides further evidence of ongoing strain accumulation and release along the central Chilean margin. Continued monitoring remains essential for understanding potential links to larger seismic cycles in this tectonically active zone.

References

United States Geological Survey Earthquake Catalog
National Seismological Center of Chile (CSN) reports
SeismoSight internal swarm classification data