UPDATED 10.03AM Tsunami waves of 30cm have hit the east coast of the North Island following a massive undersea earthquake and Civil Defence says the worst has passed.

People are still being urged to stay away from the coast and waterways from Northland down to south of Gisborne this morning, following the 7.1-magnitude quake.

The quake struck at a depth of 55km, 130km northeast of Te Araroa about 4.37am, with a series of aftershocks continuing through the morning. A 30cm wave was measured at East Cape and Great Barrier Island.

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Just before 8.30am Civil Defence cancelled its tsunami marine and beach threat warning.

"Based on all available data, the greatest tsunami activity has now passed," it said.

"However, coasts may still experience unusual, strong currents and sea level fluctuations lasting for several more hours."

Earlier, it said East Cape, Bay of Plenty and Gisborne would experience waves and currents of less than 20cm.

People in Gisborne, who were earlier told to seek higher ground, were told return to their homes.

Schools in the region would be open on Friday, except for Tolaga Bay Area School, which had made an early call on school buses.

However, Civil Defence says unusually strong currents and unpredictable flows could be expected.

In Auckland the Britomart train station was earlier shut down as a precaution - causing large disruption to morning commutes.

Gisborne controller John Clarke says surges of about 30cm have been recorded at Gisborne port and the gauge at East Cape, "which enforces the need for people to stay away from the coast".

More than 4000 people, from as far south as Christchurch and the West Coast, reported feeling the 7.1 quake.

However, the Fire Service said there were no reports of damage.