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Location:
Bonin Islands, Japan region
Period:
21 Dec 2010 17:19:40 - 23 Dec 2010 14:30:40 (1 day 21 hours 11 minutes)
Volcanoes in 100km radius:
None
Earthquakes:
52
M 7.0+:
M 7.4; Bonin Islands, Japan region; (21 Dec 2010) (12km from the swarm center)
7 swarms found nearby.
2010
S20101222.3(33.8km)
21 Dec
4 days 11 hours
81 earthquakes
21 Dec
4 days 10 hours
92 earthquakes
S20101222.2(36.3km)
21 Dec
4 days 22 hours
86 earthquakes
S20101222.4(46.1km)
21 Dec
2 days 11 hours
37 earthquakes
24 Dec
1 day 15 hours
8 earthquakes
2011
PS20110124.1(45.5km)
23 Jan
14 hours
5 earthquakes
2024
PS20241107.1(192.5km)
6 Nov
20 hours
7 earthquakes
AI-generated article — for informational and entertainment purposes only. May contain inaccuracies. Full disclaimerFound an error?

Seismic Swarm PS20101221.1 in the Bonin Islands Region

A notable seismic swarm designated PS20101221.1 occurred in the Bonin Islands, Japan region, from 17:19 on 21 December 2010 to 14:30 on 23 December 2010. Over this 45-hour period, 52 earthquakes were recorded, highlighting the dynamic tectonic environment of the area.

The swarm initiated with a magnitude 7.4 event at 17:19:40 on 21 December at a depth of 14 km. Subsequent activity included numerous events between magnitudes 5.0 and 6.4, with depths predominantly ranging from 2 km to 18 km. Notable later shocks comprised a magnitude 6.4 earthquake on 22 December at 21:49:40 (18 km depth) and several magnitude 5.5–5.6 events clustered in the initial hours. The sequence concluded with a magnitude 5.0 event at 14:30:40 on 23 December.

This activity aligns with the broader seismicity of the Bonin Islands, situated along the Izu-Bonin-Mariana arc system. Here, the Pacific Plate subducts westward beneath the Philippine Sea Plate at rates of approximately 4–6 cm per year, generating both shallow crustal events and deeper Wadati-Benioff zone earthquakes. The arc features volcanic islands and seamounts formed by this subduction, with the region experiencing recurrent moderate-to-large earthquakes due to plate interface coupling and intra-plate deformation.

Historically, the Bonin Islands have hosted significant seismic events, including deep-focus earthquakes exceeding magnitude 7. The 2010 swarm's proximity to a magnitude 7.4 mainshock underscores patterns of clustered aftershock-like activity in subduction forearc settings. Depths in the recorded data reflect a mix of shallow crustal and upper-plate seismicity typical of the overriding Philippine Sea Plate.

Such swarms provide insights into stress redistribution following large ruptures, often without a single dominant mainshock. Monitoring in this tectonically active zone supports improved understanding of subduction dynamics and regional hazard assessment.

References

  • SeismoSight internal swarm classification data (PS20101221.1 event parameters).
  • USGS Earthquake Catalog for Bonin Islands regional tectonics and historical seismicity.