Japan quake and tsunami 'did not trigger' New Zealand north island quake

A 6.9 earthquake and the following tsunamis did not trigger a 5.6 earthquake near New Zealand's north island, an earthquake expert says.

A United States Geological Survey map of the most recent New Zealand earthquake. Source: United States Geological Survey

A strong earthquake has struck off the coast of New Zealand's North Island but there have been no immediate reports of damage or injuries.

The quake, first reported as 6.3 magnitude but later downgraded to 5.6, was centred about 200 kilometres northeast of the capital Wellington, according to the US Geological Survey. It was at a relatively shallow depth of 10 kilometres.

The Pacific Tsunami Warning Center did not issue a tsunami warning.

New Zealand was last week hit with a powerful magnitude 7.8 quake near the coastal South Island town of Kaikoura that killed two people.

New Zealand sits on the Ring of Fire, an arc of seismic faults around the Pacific Ocean where earthquakes are common. An earthquake in Christchurch five years ago killed 185 people.

It came as a 6.9 magnitude earthquake rocked Fukushima in northern Japan and generated a 1.4 metre tsunami around Sendai.

Geoscience Australia senior seismologist Hugh Glanville says both events on Tuesday happened on the edge of the Pacific plate, but that's where any connection ends.

"They are so far apart. It's not a case of one earthquake trigging the other one," he told AAP.

"There's a bit of coincidence at play."

Mr Glanville said the New Zealand quake was a new event and was not an aftershock from the deadly 7.5 magnitude disaster that struck South Island last week.

"This is much further north than the previous ones. This is a new section of fault moving. It's not an aftershock. It's a new earthquake."

He said any damage in New Zealand would be nothing like what was seen last week.

"This one is a bit offshore and smaller than the previous one, so I wouldn't expect anything like that."

Mr Glanville said that was also true of the Japan quake, but with authorities warning of waves up to three metres, the damage could still be considerable.

"We don't expect anything like the kind of waves we saw five years ago" when a very large earthquake generated a devastating tsunami that wiped out parts of Fukushima prefecture, and knocked out a nuclear power plant, spilling radiation into the air and sea.