Seismic Swarm PS20241017.1 Recorded in Kermadec Islands Region

A seismic swarm designated PS20241017.1 was recorded in the Kermadec Islands region between 17:11 on 16 October 2024 and 10:33 on 17 October 2024. The sequence lasted 17 hours and 22 minutes and included five earthquakes. Event times, magnitudes, and depths were as follows: a magnitude 5.1 event at 10 km depth on 16 October at 17:11; a magnitude 5.0 event at 10 km depth on 16 October at 18:59; a magnitude 5.6 event at 12 km depth on 17 October at 05:37; a magnitude 4.5 event at 10 km depth on 17 October at 10:23; and a magnitude 5.0 event at 10 km depth on 17 October at 10:33.

The Kermadec Islands occupy a tectonically active segment of the Pacific Ring of Fire. They sit above the Kermadec-Tonga subduction zone, where the Pacific Plate descends beneath the Australian Plate along the Kermadec Trench. This convergent margin produces frequent shallow to intermediate-depth earthquakes and occasional deeper events. The trench reaches depths exceeding 10,000 meters and forms part of the longest subduction system on Earth.

Seismic swarms are common in this setting. Since 1 January 2000, nineteen swarms have occurred in the region. Earlier episodes took place in 2005 (two), 2006 (two), 2011 (one), 2012 (one), 2016 (one), 2020 (one), 2021 (seven), 2022 (two), 2023 (one), and 2024 (one). These clusters typically involve moderate-magnitude events at shallow depths and reflect episodic stress release along the plate interface or within the overriding plate.

A magnitude 7.0 earthquake struck the same general area on 18 February 2009, with its epicenter located 51 km from the center of the recent swarm. That event remains the strongest recorded in the immediate vicinity since 2000. The ongoing swarm, while energetic, stayed below magnitude 6.0 and produced no reported damage given its offshore location.

Continued monitoring of the Kermadec subduction zone remains essential. The combination of rapid plate convergence and historical swarm activity indicates that moderate seismic sequences will recur. Data from networks such as GeoNet and the USGS provide the primary observations used to track these patterns and refine regional hazard assessments.