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Location:
south of the Fiji Islands
Period:
26 Feb 2012 02:46:21 - 27 Feb 2012 14:54:55 (1 day 12 hours 8 minutes)
Volcanoes in 100km radius:
Unnamed(16km)
Earthquakes:
16
6 swarms found nearby.
2004
PS20040410.1(111.4km)
10 Apr
17 hours
5 earthquakes
2010
PS20100222.1(167.2km)
22 Feb
23 hours
6 earthquakes
2011
PS20110630.1(192.8km)
30 Jun
9 hours
5 earthquakes
2017
PS20171016.1(189.9km)
16 Oct
17 hours
7 earthquakes
2023
PS20230616.1(170.7km)
16 Jun
2 days 9 hours
20 earthquakes
PS20230625.1(171.0km)
25 Jun
7 hours
5 earthquakes
AI-generated article — for informational and entertainment purposes only. May contain inaccuracies. Full disclaimerFound an error?

Seismic Swarm PS20120226.1: Analysis of Seismic Activity South of the Fiji Islands

A notable seismic swarm, designated PS20120226.1, occurred south of the Fiji Islands from 02:46 on 26 February 2012 to 14:54 on 27 February 2012. Over 36 hours and 8 minutes, the swarm comprised 16 earthquakes, with magnitudes ranging from 4.4 to 6.0 and focal depths predominantly between 2 km and 100 km. This event highlights the region's persistent tectonic instability within the southwestern Pacific.

The sequence began with two events of magnitude 5.5 at 02:46 on 26 February, occurring at depths of 10 km and 60 km. Activity intensified with a magnitude 6.0 earthquake at 05:21 at 10 km depth. Subsequent events included a magnitude 4.4 at 09:07, followed by multiple shocks of 5.0 to 5.2 throughout the day at shallow depths around 10-15 km. On 27 February, additional events clustered around 03:01 and 14:34-14:54, including a shallow 5.2 at 2 km depth and a deeper 5.0 at 100 km. These patterns indicate a mix of shallow crustal and intermediate-depth activity typical of subduction-influenced zones.

Geologically, the area south of Fiji lies at the complex junction of the Pacific, Australian, and Tonga plates. This region features the northern extension of the Tonga subduction zone and associated transform faults, driving frequent seismicity through plate convergence and back-arc spreading. Historical records confirm elevated earthquake rates due to these dynamics, with the Fiji Plateau acting as a diffuse boundary accommodating oblique subduction.

Since 2000, only three prior swarms have been documented in this locale, occurring in 2004, 2010, and 2011. Each involved limited event counts, underscoring the relative infrequency of clustered activity compared to isolated mainshock-aftershock sequences. The 2012 swarm aligns with this sparse historical distribution while demonstrating a higher event total.

Such swarms provide insight into stress migration along fault networks without a dominant mainshock. Depths varying from near-surface to 100 km suggest activation across multiple structural levels, potentially linked to fluid migration or slab dehydration in the subducting Pacific plate.

References

SeismoSight Internal Database: Swarm Classification PS20120226.1
USGS Earthquake Catalog: Regional Seismicity South Pacific (2000-2023)
Global CMT Project: Focal Mechanism Data for Tonga-Fiji Region