Changes in water level - seen as a precursor to a tsunami - have been seen is Gisborne, and gauges show changes in the Hawke's Bay and at Castlepoint, on the Wairarapa coast.
Initial surges were likely to be smaller than those to follow, Civil Defence warned. It was expected that the greatest wave heights could occur between six and 12 hours after the initial arrivals.
Rana Solomon of Chatham Islands Council reported a wave height of 1.5 metres at Pitt Island in the Chathams, Civil Defence said.
"Gisborne, Napier and Castlepoint tsunami gauges are also showing initial activity of approximately the same magnitude as East Cape.
"It is important to note that these are the first arrivals and larger waves may follow over a period of several hours. The situation continues to be closely monitored."
The Pacific Tsunami Warning Centre (PTWC) issued a tsunami warning in response to the above earthquake.
Confirmation has been received that a tsunami was generated. A wave measuring 2.34m was measured at Talcahuano, Chile and 0.35m at Easter Island, Chile.
The Tsunami Experts Panel said a threat to beachs and small boats existed for the entire east coasts of the North and South Island from Puysegur Point on the Southland west coast, around to Cape Reinga and extending south to Ahipara, on the Far North west coast.
Some land threat also existed for the Chatham Islands and Banks Peninsula, with the possibility of one-three metre waves.
Sea levels along the Gisborne coast have dropped dramatically, prompting authorities to close roads to beaches and clear away sightseers.
Waikanae Beach Holiday Park manager Diane Ross said that just as residents were starting to return to their beachfront homes, the sea suddenly receded about 9.20am. It was almost high tide when the water pulled out to below the low tide mark.
It dropped about 1-1.5 metres in the space of a matter of moments, Ms Ross told Radio New Zealand. The water went "very, very brown", indicating that it was being stirred up by swirling currents, she said. All the holidaymakers at the campground had been evacuated early this morning and were watching the action from a marae at nearby Kaiti Hill.
Gisborne Civil Defence controller John Davies confirmed the witness reports, saying the sea had dropped about a metre and while it had not surged back in, there was "unsual" wave activity happening.
The wave movement was clearly building and it was essential people kept away from the coastline for the next 10-12 hours, he said. There were still "idiots" been seen heading to the beach with surfboards on their cars, a Gisborne witness said.
By 8am when the wave was due to arrive, hill tops in and around Gisborne were chocabloc with people and cars. On Kaiti Hill overlooking the city and port, a few people could also be seen on the city beachfront below, waiting to watch for a wave.
On the Chatham Islands, residents have seen big changes in water level.
Chatham Islanders took to what little high ground there is, after warnings that a major earthquake in Chile overnight had generated a tsunami.
One resident said sea levels had changed dramatically.
"Everyone's gone to higher ground we are on higher ground but we've got a perfect view of the bay," Chris told NZPA. She did not want to give her surname.
"The water is starting to disappear from round the bay, all the rocks are uncovered, the water is definitely moving out. Now the rocks are covered up again. There's no big wall of water yet. It looks very unusual, very unusual.
"It's kind of high tide here at the moment but sort of in no time the rocks became uncovered but they're covered up again. It's (happening) very slowly." Everyone was relatively safe and all the civil defence mechanisms were in place, she said.
Sightseers keen for a glimpse of the predicted tsunami are hitting the roads to Hawke's Bay's coast. Emergency services said the tsunami danger message did not appear to have gotten through to many people, who were heading for areas in the process of being evacuated.
The coastal settlements of Ocean Beach and Waimarama have been evacuated, and police were door-knocking at Haumoana and Te Awanga, warning residents it would be a good idea to leave.
Eleven houses right on the beach at Te Awanga were particularly at risk. One of those residents was recently prosecuted for building an illegal sea wall to stop the heavy seas eroding his backyard.
Sightseers keen for a glimpse of the predicted tsunami were hitting the roads to the coast.
Emergency services said the tsunami danger message did not appear to have gotten through to many people, who were heading for areas in the process of being evacuated.
Ken Gledhill of GNS Science said New Zealand was not in the main beam of the tsunami, which was headed for Japan.
It was still expected to hit this country, and a lack of recorders across the Pacific Ocean from Chile meant it was hard to predict how big the tsunami would be.
Four major waves had hit French Polynesia, Tahiti had a water level rise of up to two metres, with little damage, and the water was being sucked out and returning at a higher level the Chatham Islands, though the full force had yet to arrive.
Dr Gledhill said "we can say it's unlikely to be very destructive". The tsunami would be mainly a marine threat, he told TVNZ. Some pockets could be worse than others.
