Location:

Period:

26 Nov 2023 11:42:59 - 27 Nov 2023 04:23:13 (16 hours 40 minutes)

Volcanoes in 100km radius:

None

Earthquakes:

3 swarms found nearby.

2005

PS20050810.1(28.8km)

9 Aug

19 hours

5 earthquakes

2016

PS20160812.1(179.8km)

12 Aug

20 hours

7 earthquakes

2019

PS20191226.1(116.8km)

25 Dec

22 hours

6 earthquakes

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Seismic Swarm PS20231127.1 in the Vanuatu Region

A seismic swarm designated PS20231127.1 occurred in the Vanuatu region between 11:42 on 26 November 2023 and 04:23 on 27 November 2023. Over 16 hours and 40 minutes, five earthquakes were recorded, with magnitudes ranging from 4.5 to 5.5 and focal depths consistently at 10 km. The sequence began with a magnitude 5.4 event at 11:42:59 on 26 November, followed by a magnitude 5.5 shock at 03:31:15 on 27 November. Subsequent events included magnitudes 5.4 at 03:56:01, 5.2 at 04:17:39, and 4.5 at 04:23:13, all on 27 November.

Vanuatu lies within the tectonically active Pacific Ring of Fire, where the Pacific Plate subducts beneath the Australian Plate along the New Hebrides Trench. This subduction zone drives frequent seismicity and volcanism across the island arc. The region experiences some of the world's highest rates of earthquake activity due to rapid plate convergence exceeding 10 cm per year in places. Historical records document major events, including the 1994 magnitude 7.1 earthquake near Efate and the 2009 magnitude 7.8 event that generated a tsunami.

Since 2000, only three prior swarms have been identified in the Vanuatu region according to internal classifications: one in 2005, one in 2016, and one in 2019. The current swarm aligns with typical patterns of clustered shallow seismicity in subduction settings, where stress transfer along the plate interface can trigger multiple moderate events over short periods without producing a single dominant mainshock.

Such swarms contribute to ongoing monitoring efforts that help refine seismic hazard assessments for Vanuatu's population centers. Shallow depths around 10 km increase the potential for felt shaking on nearby islands, though no significant damage was associated with this sequence. Continued observation supports improved understanding of subduction dynamics in one of Earth's most seismically energetic zones.

References:
USGS Earthquake Catalog
Global CMT Project
Pacific Tsunami Warning Center historical reports