Three Quakes Strike off Vanuatu Near Port-Olry on Sunday

Three earthquakes struck off Vanuatu in the South Pacific on Sunday morning, all within about 200 kilometres northwest of Port-Olry on the island of Espiritu Santo, the US Geological Survey reported. The strongest was magnitude 5.4, at 06:26 UTC, at a depth of 10 kilometres. A magnitude 5.1 followed at 07:00 UTC, and a magnitude 4.7 at 07:37 UTC, in the same patch of ocean.

No tsunami warning, watch or advisory was issued for any of the three, and the Geological Survey's automated PAGER assessment for the largest quake was green, the level that signals a low risk of casualties and damage. No felt reports had been filed for the 5.4 quake in the first hours after it struck, and no damage had been reported from Port-Olry or the surrounding islands by mid-morning.

A week of shaking in the same waters

The Sunday sequence is the latest in a run of quakes in the same zone. A magnitude 5.2 struck 200 kilometres northwest of Port-Olry late on Saturday, at 22:42 GMT, Xinhua reported from the Geological Survey's data. On October 24, a magnitude 7.2 earthquake struck off Vanuatu near Sola, strong enough to bring a tsunami warning for nearby coasts at the time. Port-Olry sits on the northeast coast of Espiritu Santo, Vanuatu's largest island.

Vanuatu sits on the Pacific Ring of Fire, where the Australian plate dives beneath the Pacific plate. The Geological Survey's catalogue counts dozens of quakes above magnitude 4 within 250 kilometres of Sunday's epicentres over the past month, most of them small and far offshore.

What happens next

Seismologists treat clusters like this as aftershock sequences or swarms until the pattern settles. The practical risk from Sunday's three quakes is low: they were offshore, moderate, and shallow only in the technical sense, with their energy released under open ocean about 200 kilometres from the nearest town. Officials in Vanuatu had issued no alerts beyond the routine by the time this report was filed. The number to watch is whether the sequence produces a quake above magnitude 6, which would change the picture for the islands.

Ten kilometres is shallow for this zone, but distance did the protective work on Sunday. At about 200 kilometres offshore, even a shallow quake loses most of its force before it reaches land. That distance is why the Geological Survey recorded no felt reports, and why the morning's three quakes stayed a monitoring story rather than becoming a damage story.