Evacuation warnings as tsunami wave hits Chatham Islands

An aerial view of the Chatham Islands. Photo / Janna Dixon

A wave measuring half a metre has reached the Chatham Islands this morning and New Zealand's entire east coast has been put on tsunami alert.

Official tsunami warnings are in place for the entire east coast after a massive earthquake hit Chile overnight.

The first wave that reached the Chatham Islands, measured 20cm, according to GNS Science, but authorities warn that succeeding waves could be higher. It was followed by a second wave measuring half-a-metre.

GNS Science staff said the waves had reached monitoring equipment off the coast of the Chathams and could slow have slowed down by 20 to 30 minutes. The wave could be further slowed by the continental shelf.

The Civil Defence Emergency Management office has put a warning in place for the entire east coast of New Zealand and warn that a tsunami between one and three metres could be on its way after an 8.8 magnitude earthquake in Chile over night.

The wave was scheduled to reach the Chatham Islands by 7.05am.

GNS Geonet project director Ken Gledhill said the wave began to arrive at 720am.

"Its built now to around 30cms high and it's likely to carry on building for the next few hours," Mr Gledhill said earlier this morning.

"There's always big uncertainties and that's the biggest issue for Civil Defence. When you tell them it might be between 1m and 3m at the beach, that's quite a wide range but it's the kind of uncertainty we have to deal with. Add to that uncertainties in timing where the first wave probably won't be the biggest one unless you're quite near the source.

"The message is - you probably don't have to go to the beach today. It's probably better if you don't," he said.

He said people wanting to see the wave would have to be "significantly above sea level" to be safe.

"The problem with these events are ... if you have two parts of the wave train that add together you can suddenly get a bigger wave. that's why it's probably easier to get a better idea when you are in the main beam of the event rather than on the side like we are," Mr Gledhill said.

He said for most of the country, the tsunami is a marine threat.

"That means if you go to the beach or on a small boat you could have an issue. We are still talking about less than a metre for most of New Zealand, but there's potential for the Chatham Islands and Banks Peninsula for something more than that (1m to 3m)," he said.

"One metre is not considered to be a destructive tsunami except if you're in the wrong place and it washes you out to sea. There'll be extra currents too. The currents will be crazy, probably for days.

"Apart from if you're unlucky and happen to be in one of these places where the wave gets amplified for some reason, it won't probably be too serious. That's our prediction at the moment. Hopefully it stays like that," Mr Gledhill said.

Meanwhile, many New Zealanders were going about their usual Sunday morning activities, blissfully unaware of the danger.

On Auckland's North Shore, people said they were unaware of the warning, which was sparked by an 8.8 magnitude earthquake in Chile last night.

Several boaties who were about to head out were alarmed at the prospect of a metre-high wave hitting the east coast and were reconsidering their day on the water.

At Milford Beach two women who were about to set off on a walk along the coast to Takapuna were apparently unperturbed about the warning and did not change their plans.

"I've got my flippers," said one of the women.

The tide in Auckland was very high shortly after daybreak and many houses on beaches and in the east coast bays were likely to feel the impact of a metre-high wave if it hits Auckland.

However it appears the warning had not reached many people and there were still boats being launched.

On a bay north of Milford a man was fishing off a rocky outcrop.

At Whitianga a resident told NZPA that a warning siren had gone off, but residents didn't know what it was, so stayed put.

In Gisborne a voluntary evacuation was underway of residents at Midway and Waikanae beaches, but in Napier stall-holders were setting up their Sunday market on the foreshore.

They said they preferred to wait until they had heard what had happened in the Chathams before packing up and moving inland.

On the Chatham Islands, Catherine McKenzie is working at the Chatham Lodge, situated inland near the Henga Scenic Reserve.

About 40 locals have left their homes on the coast and gathered at the lodge to watch the news and listen to the news on the radio.

"This is a safe place, a high place," Ms McKenzie said.

She said she was called by her boss at 3am and people began turning up two hours later.

The quake which has sparked the tsunami warnings hit 325 kilometres southwest of Santiago, at a depth of 35 kilometres at 3.34am local time (6.34pm NZT), the US Geological Survey reported.

A wave measuring 2.34 metres was recorded near Chile and Tsunami warnings were issued over a wide area in the Pacific.

The New Zealand Ministry of Civil Defence and Emergency Management (CDEM) said areas of land could be threatened on the Chatham Islands and Banks Peninsula, while waves of less than 1 metre were likely for the entire east coast of New Zealand.

The township of Waitangi in the Chathams at 7.05am and was the first New Zealand landmark scheduled to be hit, according to the CDEM warning.

"The first wave may arrive later and may not be the largest. Strong currents and unusual tidal effects may continue for several hours," the warning said.

Canterbury CDEM group said residents in low lying areas of Banks Peninsula bays, where the tsunami was expected to arrive about 8.30am, should be prepared for an evacuation.

"People need to be ready to move to safety by 8am and may not be able to return for at least 24 hours."

People on coastal areas were asked to stay off beaches, avoid the water (including rivers and estuaries) and refer to media or their local Civil Defence authorities for updates.

The ministry asked that people avoid calling 111 for information, reserving that number for emergencies.

Estimates show the first wave reaching the east coast of the North Island by 8am ahead of the main centres of Wellington (8.25am), Christchurch (9.05am) and Auckland (10.22am).

However, those times have now been put back by between 20 and 30 minutes.

In Auckland, a half marathon has been cancelled at Okahu Bay. Signs have been put up alerting competitors to the cancellation and speakers have been set up to broadcast National Radio.

- With NZPA