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Tsunami advisory ended after magnitude 8.0 earthquake off New Zealand

Last Updated Mar 4, 2021 at 8:58 pm EDT

Location of earthquake that struck off the North island of New Zealand on March 5. GOOGLE MAPS

One of the strongest earthquakes to hit the South Pacific in modern history triggered tsunami warnings across the ocean and forced thousands of people in New Zealand to evacuate coastal areas Friday. Small tsunami waves were seen but little damage was apparent hours later.

The magnitude 8.1 quake in the Kermadec Islands region about 1,000 kilometres (620 miles) from New Zealand was the largest in a series of tremors, including two earlier quakes that registered magnitude 7.4 and magnitude 7.3.

The tsunami threat caused traffic jams and some chaos in New Zealand as people scrambled to get to higher ground.

Residents recorded videos of small wave surges in some places, including at Tokomaru Bay near Gisborne.

The largest quake struck about 1,000 kilometres (620 miles) off the coast of New Zealand. One of the earlier quakes hit much closer to New Zealand and awoke many people as they felt a long, rumbling shaking.

“Hope everyone is ok out there,” New Zealand Prime Minister Jacinda Ardern wrote on Facebook during the night.

After the largest quake, civil defence authorities in New Zealand told people in some coastal areas to immediately get to higher ground.

In the afternoon, the National Emergency Management Agency said the threat had passed and people could return to their homes, although they should continue avoiding beaches.

The Pacific Tsunami Warning Center said ocean gauges had measured tsunami waves of 30 centimetres (1 foot) in Vanuatu and said waves of similar size could cross the Pacific to Latin American coasts

Emergency Info BC said there was no tsunami risk to the coast.

The U.S. Tsunami Warning System also cautioned the quake could cause tsunami waves of up to 3 metres (10 feet) in Vanuatu and up to 1 metre (3 feet) in Australia, Fiji, French Polynesia and as far away as Mexico and Peru.

The U.S. Geological Survey said it was centred near the remote Kermadec Islands at a depth of 19 kilometres (12 miles).

The agency said in a report that the quake occurred at the intersection of the Pacific and Australia tectonic plates and eclipsed the largest quake previously recorded in the region, a magnitude 8.0 in 1976.

It said the interaction between the plates creates one of the most seismically active regions in the world, and it has recorded 215 quakes there above magnitude 6.0 over the past century.

Jennifer Eccles, an earthquake expert at the University of Auckland, said the quake was at the top end of the scale for those involving only the Earth’s ocean crust.

“This is about as big as it gets,” she said.

She said most quakes larger than magnitude 8.0 tend to occur when a section of more robust continental crust is involved.

The U.S. Geological Survey said the magnitude 7.4 quake was likely a “foreshock” that contributed to the larger quake but that the first quake that hit closer to New Zealand was too far away in time and distance to have directly contributed.

Officials in New Zealand had hours earlier issued a tsunami warning for coastal areas after the first quake struck off its northeastern coast at about 2:30 a.m. Friday. There were no immediate reports of serious damage or casualties, and the warning was lifted just before the largest quake hit.

The U.S. Geological Survey said the first quake was centred at a depth of 21 kilometres (13 miles) under the ocean about 174 kilometres (108 miles) northeast of the city of Gisborne.

It was widely felt in New Zealand, and residents in the major cities of Auckland, Wellington and Christchurch reported being shaken awake.

In 2011, a magnitude 6.3 quake hit the city of Christchurch, killing 185 people and destroying much of its downtown.