A tsunami sparked by a powerful 7.6-magitude quake failed to materialise on New Zealand's shores, but Civil Defence says people should expect high tides within the next 24 hours.

In Auckland and other parts of the east coast of the North Island, authorities said there was an increased swell in coastal areas but little to cause concern. On the east coast of Northland there were significant swells about 10am.

New Zealand Civil Defence said it expected a swell generated by the quake to cause strong currents but not damage to the land. Tsunamis had struck the Kermadec Islands and Raoul Island this morning.

For the next 24 hours people were urged to exercise caution before entering the water or going out in small boats.

The quake struck at 7.03am (NZT) at a depth of 20km, according to the US Geological Service. It was felt in Wellington and parts of the East Coast of the North Island.

GNS tsunami scientist Dr William Power said the largest waves moved to the east and west of the epicentre, with very little energy sent south towards New Zealand.



The largest observed wave height was 1.9 metres at the two tsunami gauges at Raoul Island, which put the top of the wave at about one metre above the normal tide level.



Small tsunami arrivals, not much larger than normal ''sea noise'', were subsequently observed on tsunami gauges at Great Barrier Island and East Cape, Power said.



It was best to err on the side of caution when issuing warnings, he said.



"It's a difficult judgement call, but in this case it was appropriate to issue a tsunami warning and then downgrade it later as more information came to hand."

Dive Tutukaka, which is based in the Tutukaka Harbour just north of Whangarei, cancelled three or four dive charters out to the Poor Knights Islands today because of the swells and a gale warning for later today and tomorrow.

Dive Tutukaka's Kate Malcolm said the water was calm and flat but there was a rise and fall of about half a metre in the harbour and they were expecting that to continue for possibly six hours.

"We were expecting a short, sharp increase (in surges) and that is what we are seeing at the moment."

She said the current in and out of the harbour was about six knots. On most days there was little or no current.

"We have got some whirlpool action and it is draining really quickly."

"We are seeing a lot of stir-up on the bottom. It is churning and it is very muddy," said Ms Malcolm.

In Hawke's Bay and the East Coast there was stronger than usual currents and unusual tidal action and people were advised to stay away from the coast.

Occupants at the Te Awanga and Clifton Beach motor camps and Ocean Beach settlement in Hawke's Bay were evacuated this morning and residents of 21 homes along the Haumoana waterfront were also asked to move out as a precaution.

People were urged to stay off the beaches, stay out of the water and not go sightseeing in the coastal areas until well after the surge threat had passed.

Civil Defence had earlier activated its National Crisis Emergency Management Centre.

KERMADEC ISLANDS SHAKEN

Eight people on Raoul Island - right next to the epicentre - are safe and unharmed from this morning's massive earthquake.

An aftershock measuring 5.6 rattled the Kermadecs at 8.35am, at a depth of 10 km deep.

The Department of Conservation said it had four staff and four volunteers on the island.

"They certainly felt the earthquake but they are fine," a DOC regional spokesman Liz Maire said.

There was no obvious sign of damage and the staff had not seen a tsunami which would already have hit the island.

Maire said they were now out on the island looking for damage to tracks.

She said the staff were cautious of aftershocks and were taking precautions.

Meanwhile, a Tonga police official said the quake was not felt on Tongatapu.

- PALOMA MIGONE, NZPA, MICHELLE COOKE, and MICHAEL FIELD/Stuff, with THE DOMINION POST

