Location:

Period:

5 Mar 2010 09:19:36 - 6 Mar 2010 15:19:06 (1 day 5 hours 59 minutes)

Volcanoes in 100km radius:

None

Earthquakes:

9 swarms found nearby.

2010

PS20100227.2(43.9km)

27 Feb

2 days 9 hours

41 earthquakes

PS20100227.3(132.5km)

27 Feb

1 day 20 hours

28 earthquakes

PS20100227.6(124.4km)

27 Feb

13 hours

10 earthquakes

PS20100302.1(90.5km)

2 Mar

1 day 13 hours

7 earthquakes

PS20100310.1(57.3km)

10 Mar

6 hours

5 earthquakes

PS20100313.1(17.0km)

13 Mar

17 hours

6 earthquakes

PS20100316.1(100.7km)

15 Mar

16 hours

5 earthquakes

2011

PS20110211.1(58.3km)

11 Feb

5 hours

7 earthquakes

2015

PS20150319.1(126.2km)

18 Mar

14 hours

5 earthquakes

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Seismic Swarm PS20100305.2 Off Talcahuano, Chile: Geological Context and Event Analysis

Seismic swarm PS20100305.2 occurred in the offshore region 56 km west of Talcahuano, Chile, beginning at 09:19 on 5 March 2010 and concluding at 15:19 on 6 March 2010. Over this 29-hour 59-minute period, seven earthquakes were recorded, with magnitudes ranging from 4.3 to 6.6 and focal depths between 3 km and 37 km. This activity unfolded in the immediate aftermath of the magnitude 8.8 Maule earthquake of 27 February 2010, within the tectonically active Chilean subduction zone.

The events unfolded as follows. The sequence initiated with a magnitude 6.1 shock at 29 km depth on 5 March at 09:19:36 UTC. A magnitude 5.2 event followed at 37 km depth roughly one hour later. The largest event, magnitude 6.6 at 18 km depth, occurred at 11:47:06. Subsequent shocks included two magnitude 5.2 events at 35 km depth, a shallow magnitude 4.3 at 3 km depth, and additional magnitude 5.1 and 5.2 events at 10 km and 35 km depths on 6 March. These earthquakes clustered tightly in both time and space, characteristic of swarm behavior rather than a classic mainshock-aftershock sequence.

The location lies along the convergent boundary where the Nazca Plate subducts beneath the South American Plate at rates of approximately 6–7 cm per year. This tectonic setting has produced some of the largest earthquakes on record, including the 1960 Valdivia event and the 2010 Maule rupture, which extended over 500 km along the plate interface and generated significant afterslip and viscoelastic relaxation in the months that followed. The swarm’s shallow to intermediate depths align with the seismogenic portion of the megathrust and overlying crustal faults, where stress perturbations from the preceding great earthquake likely promoted failure on multiple nearby structures.

Since 1 January 2000, four seismic swarms have been documented in the broader region, with this event representing the first. Such episodic clusters provide insight into post-seismic stress transfer and fluid migration along the plate interface, processes that can sustain elevated seismicity for weeks to months after a major rupture. Monitoring data from this swarm contribute to refined models of subduction-zone segmentation and recurrence intervals for intermediate-magnitude events along the central Chilean margin.

References

USGS Earthquake Catalog, Maule 2010 sequence and aftershocks.
Servicio Nacional de Geología y Minería (SERNAGEOMIN), Chile seismic reports 2010.
Oncken et al., 2014, “Seismic and geodetic constraints on the Maule earthquake afterslip,” Tectonophysics.