Undersea earthquake strikes in South Pacific, triggering tsunami warnings

An undersea earthquake has struck in the South Pacific, triggering tsunami alerts in New Zealand, Fiji and other Pacific islands.

The 7.7 magnitude quake’s epicentre was 10km underwater and around 400km to the east of North Caledonia, according to authorities.

The earthquake, which struck just after midnight on Thursday local time (1.20pm Wednesday GMT), followed at least three other tremors - with magnitudes ranging from 5.7 to 6.1 - that hit the South Pacific region in the space of just over an hour.

There were no immediate reports of damage near the epicentre in New Caledonia, John Ristau, a seismologist from GNS Science, a New Zealand research institute, said.

"It's most likely that damage would have been minimal if anything at all," he told told NewsHub's The AM Show.

A number of smaller earthquakes followed in the wake of the 7.7 magnitude quake around the same area southwest of Loyalty Islands, according to the US Geological Survey.

The US Tsunami Warning Centre issued tsunami watches for New Zealand, Fiji, Vanuatu and other Pacific islands following the largest tremor, which have now been removed.

"Based on the most recent modelling and decreasing tsunami amplitudes at North Cape, Great Barrier Island and the East Cape, the tsunami threat has passed for New Zealand," the country's National Emergency Management tweeted on Thursday morning (9pm Wednesday GMT).

"There could still be large unexpected currents and the public are advised to continue to take precautions in coastal zones for the rest of today."

After the earthquake struck, the New Zealand agency told people to get out of the water and to stay away from beaches and harbours in areas from Ahipara to Bay of Islands, Great Barrier Island and from Matata to Tolaga Bay.

"We expect New Zealand coastal areas to experience strong and unusual currents and unpredictable surges at the shore," the agency said.

"Strong currents and surges can injure and drown people. There is a danger to swimmers, surfers, people fishing, small boats and anyone in or near the water close to shore."

Australia issued a marine tsunami threat to Lord Howe Island, a marine reserve more than 700km northeast of Sydney, following the earthquake but said evacuations were not necessary.

This tsunami alert was removed later on Thursday morning local time (8pm GMT), with government’s bureau of meteorology saying “small unusual waves may continue” but these are “no longer expected to be dangerous”. 

The region is prone to earthquakes because it sits along the Pacific "Ring of Fire," a horseshoe-shaped series of seismic fault lines around the ocean.

Additional reporting by agencies