Tsunami threat passes following earthquake off New Caledonia

February 11, 2021

The National Emergency Management Agency (NEMA) says the tsunami threat has passed for New Zealand after a magnitude 7.7 earthquake near New Caledonia but people should still continue to take precautions.

The undersea earthquake struck south east of the Loyalty Islands at 2.20am triggering a NEMA national advisory for New Zealand.

NEMA said 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.

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, it said.

At Ahipara, on the southern end of Ninety Mile Beach on Northland's west coast, local man Paul Hansen said surge waves were pushing the water 30-40 metres further up the beach than usual.

Hansen, who lives above the beach, watched the surge come in from his house.

"I would expect the water to be sitting around about the mid-tide mark but on a reasonably regular basis what we're seeing is the water move right through to a high-tide mark.

"I will definitely be staying off the beach."

He said the beach entrances had been blocked off and he couldn't see anyone along the shoreline.

A water gauge off Great Barrier Island recorded a 75cm wave just before 6am.

National Emergency Management Agency acting director Roger Ball said there was no threat to land for New Zealand, but strong currents and surges were expected in some northern areas of the country.

"In those parts of New Zealand we are asking people to stay out of the water and stay off the beaches because of the possibility of surges and unusual currents.

"We don't expect any significant change to the current advisory unless there is a subsequent seismic event and we're constantly keeping an eye out for that but we don't have any information to indicate that at this time."

GNS duty seismologist Dr John Ristau said​ there may be more earthquake activity in the South Pacific today, following the 7.7 quake.

"It's most likely that this 7.7 is going to be the main shock," he said. "However whenever you get an earthquake, particularly a large earthquake like this one, it does increase the risk for another large earthquake, even a bigger one, nearby.

"Even though that increased risk is still small, it's a possibility."

The subduction zone earthquake occurred at the boundary of the Australian plate as it pushes underneath the Pacific plate. "It wasn't close to land areas ... but it did generate a tsunami with a height of a few tens of centimetres," Ristau said.

Geoscience Australia said the quake had an epicentre 401km east of Tadine, New Caledonia. USGS said it was at a depth of 10km.

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

The US Tsunami Warning System has updated earlier advice for the Pacific that hazardous tsunami waves up to a level of 1m above the normal tide level were possible for coasts within 1000km of the epicentre, saying the threat had largely passed. - RNZ