Seismic Swarm South of the Kermadec Islands: November–December 2001

A seismic swarm designated PS20011201.1 occurred south of the Kermadec Islands, beginning at 14:13 on 30 November 2001 and concluding at 01:19 on 1 December 2001. Within approximately eleven hours, five earthquakes were recorded. All events originated at a depth of 10 km. The sequence comprised magnitudes 5.3, 5.7, 5.4, 5.2, and 4.8, respectively.

The Kermadec region forms part of the Kermadec–Tonga subduction zone, where the Pacific Plate descends beneath the Australian Plate at rates exceeding 5 cm per year. This tectonic setting produces frequent shallow to intermediate-depth seismicity and occasional large thrust earthquakes. The swarm’s uniform shallow depth and rapid succession of moderate events are consistent with stress release along the plate interface or within the overriding plate.

Historically, the Kermadec arc has generated numerous earthquakes exceeding magnitude 7.0. Notable activity includes events in 1917, 1976, and 1986. Since 2000, a magnitude 7.4 earthquake struck 62 km from the 2001 swarm center on 18 June 2020, underscoring the zone’s continued productivity.

The 2001 swarm illustrates typical clustered behavior in this highly active margin. Such sequences often occur without a single dominant mainshock and may reflect fluid migration or aseismic slip transients along the subduction interface.

References

USGS Earthquake Catalog
GeoNet New Zealand
Global CMT Catalog