The powerful earthquake that has rocked northern Japan did not trigger a smaller event off New Zealand's North Island, Geoscience Australia says.
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."
The US Geological Survey said the Japanese quake had a magnitude of 6.9 and hit off Fukushima prefecture, generating a tsunami of up to 1.4 metres in some places.
Just a few hours later, a magnitude 5.6 earthquake hit off the coast of New Zealand's North Island.
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.
