Location:

Period:

26 Jul 2023 12:44:35 - 27 Jul 2023 22:10:37 (1 day 9 hours 26 minutes)

Volcanoes in 100km radius:

Gaua(57km), Ambae(83km)

Earthquakes:

M 7.0+:

M 7.3; 48 km ENE of Luganville, Vanuatu; (30 Mar 2026) (82km from the swarm center)
M 7.1; 31 km NE of Port-Olry, Vanuatu; (20 Oct 2015) (68km from the swarm center)
M 7.1; 16 km NE of Port-Olry, Vanuatu; (9 Jan 2001) (84km from the swarm center)

14 swarms found nearby.

2000

PS20001116.1(119.2km)

15 Nov

21 hours

10 earthquakes

2008

PS20081107.1(36.4km)

7 Nov

4 hours

11 earthquakes

2009

PS20091007.1(164.4km)

7 Oct

3 days 11 hours

48 earthquakes

2010

PS20100527.1(173.9km)

27 May

21 hours

9 earthquakes

PS20100702.1(176.2km)

2 Jul

16 hours

5 earthquakes

2011

PS20110204.1(158.4km)

4 Feb

18 hours

6 earthquakes

2015

PS20150219.1(197.6km)

19 Feb

6 hours

5 earthquakes

2016

PS20160406.1(153.6km)

6 Apr

20 hours

6 earthquakes

PS20160415.1(137.8km)

14 Apr

1 day 6 hours

6 earthquakes

PS20160430.1(193.6km)

29 Apr

22 hours

5 earthquakes

2023

PS20230109.1(148.5km)

8 Jan

1 day 8 hours

6 earthquakes

PS20230302.1(142.7km)

2 Mar

6 hours

7 earthquakes

2024

PS20240722.1(107.4km)

22 Jul

9 hours

6 earthquakes

PS20240911.1(71.9km)

11 Sep

1 hours

5 earthquakes

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Seismic Swarm PS20230726.1 Near Sola, Vanuatu

A seismic swarm designated PS20230726.1 was recorded 66 km south-southeast of Sola, Vanuatu, between 12:44 on 26 July 2023 and 22:10 on 27 July 2023. Over 33 hours and 26 minutes the sequence produced nine earthquakes, beginning with a magnitude 6.4 event at 13 km depth. Subsequent events ranged from magnitude 4.4 to 5.4 and occurred at depths of 10–13 km. The swarm reflects the intense shallow seismicity typical of the central Vanuatu arc.

Vanuatu lies along the New Hebrides subduction zone, where the Australian plate converges with the Pacific plate at rates exceeding 10 cm per year. This tectonic setting generates frequent moderate-to-large earthquakes and episodic swarm activity. The July 2023 sequence occurred within the upper plate above the subducting slab, consistent with the region’s history of clustered shallow events.

Since 2000, twelve swarms have been documented in the same general area. Earlier episodes occurred in 2000, 2008, 2009, 2010 (two swarms), 2011, 2015, 2016 (three swarms), and 2023 (including the present sequence). Such recurrence indicates that swarm behavior is a persistent feature of the Vanuatu subduction interface and overlying crust.

Three strong earthquakes have also struck within roughly 85 km of the swarm center since 2000. These include a magnitude 7.1 event 16 km northeast of Port-Olry on 9 January 2001, a magnitude 7.1 event 31 km northeast of Port-Olry on 20 October 2015, and a magnitude 7.3 event 48 km east-northeast of Luganville on 30 March 2026. Each of these larger shocks further underscores the high seismic hazard of the region.

The 2023 swarm did not produce reported damage or tsunami, yet it illustrates the ongoing tectonic loading and stress release that characterize the central Vanuatu arc. Continued monitoring remains essential for understanding how such swarms relate to the occurrence of future large interface earthquakes.

References

USGS Earthquake Catalog
Global CMT Catalog
Geoscience Australia Earthquake Database