Location:

Period:

29 Sep 2019 15:57:53 - 30 Sep 2019 15:17:37 (23 hours 19 minutes)

Volcanoes in 100km radius:

None

Earthquakes:

6 swarms found nearby.

2010

PS20100227.5(95.6km)

27 Feb

3 days 19 hours

62 earthquakes

PS20100227.1(68.5km)

27 Feb

15 hours

22 earthquakes

PS20100227.6(73.3km)

27 Feb

13 hours

10 earthquakes

PS20100302.1(109.1km)

2 Mar

1 day 13 hours

7 earthquakes

PS20100316.1(97.7km)

15 Mar

16 hours

5 earthquakes

2015

PS20150319.1(86.8km)

18 Mar

14 hours

5 earthquakes

AI-generated article — for informational and entertainment purposes only. May contain inaccuracies. Full disclaimerFound an error?

Seismic Swarm S20190930.1: Offshore Maule, Chile

A seismic swarm designated S20190930.1 was recorded offshore Maule, Chile, beginning at 15:57 on 29 September 2019 and concluding at 15:17 on 30 September 2019. Over 23 hours and 19 minutes, the sequence included 28 earthquakes. The largest event reached magnitude 6.7 at a depth of 11 km, followed by numerous aftershocks and smaller events ranging from magnitude 3.0 to 5.0 at depths between 10 km and 30 km.

The sequence initiated with the mainshock and immediate smaller tremors clustered near 10–22 km depth. Subsequent activity showed a gradual decline in frequency, with events distributed across shallow to intermediate depths. Notable later shocks included a magnitude 5.0 at 13 km depth and several magnitude 4+ events persisting into the following day. Depths remained predominantly crustal, consistent with activity along the plate interface.

This swarm reflects typical behavior in subduction-zone settings, where clusters of earthquakes occur without a single dominant mainshock-aftershock pattern. Energy release was distributed across multiple events rather than concentrated in one rupture, a characteristic often linked to fluid migration or stress adjustments along the megathrust.

The Maule region lies along the Peru-Chile Trench, where the Nazca Plate subducts beneath the South American Plate at approximately 6–7 cm per year. This tectonic regime has produced some of the largest earthquakes on record, including the 2010 Mw 8.8 Maule event that ruptured a 500 km segment of the plate boundary. Offshore Maule experiences frequent moderate-to-large seismicity due to locked and creeping patches along the interface.

Historical records since 2000 indicate six swarms in the area, with five occurring in 2010 and one in 2015. These episodes underscore the region’s persistent seismic productivity, often occurring in the aftermath of major ruptures as afterslip and viscoelastic relaxation continue.

Monitoring such swarms provides insight into stress transfer and potential precursors to larger events. Continued observation by regional networks remains essential for refining hazard assessments in this high-seismicity corridor.

References
USGS Earthquake Catalog (earthquake.usgs.gov)
Global CMT Catalog (globalcmt.org)
SeismoSight internal swarm classification S20190930.1