Northlanders are being urged to take tsunami sirens seriously after some punters ignored advice to head away from the coast and instead did the opposite.

Northlanders living on the coast were evacuated early yesterday after a magnitude 7.5 earthquake, 15km northeast of Culverden in the South Island, at a depth of 15km.

Tsunami sirens were activated in Northland from 1am as a precaution after a notification that there was an imminent tsunami threat to the east coast of New Zealand.

While Northland Civil Defence Emergency Management (CDEM) advised people on the coast to head to higher ground or as far inland as possible some people did the complete opposite and headed to the coast for a good look, said Kaitaia police Acting Senior Sergeant Sarah Wihongi.


"If there's a tsunami alert people should not head to the coast to have a look, but get to higher ground as soon as possible," she said.

Northland CDEM group spokesman Graeme MacDonald said the sirens were sounded for a reason and were a warning for people to seek further information.

"Going down to the coast, people should not do that and put their lives in jeopardy," he said. "If we had what happened in the Kaikoura and people were standing on the coast, it beggars belief."

Meanwhile on the Karikari Peninsula some people slept through the sirens.

Victoria Randall, Northland Civil Defence emergency management officer, said various pathways were used to let people know what was happening including the Red Cross Hazard App and Facebook.

She said it was important people took any tsunami warning seriously.

"It was an earthquake that generated a tsunami wave close to New Zealand. Until that threat level can be established, we have to take those precautions to keep people safe and as soon as we found out what the threat levels were the information was given out to everyone. We would always say its better to be safe," she said.

Northland was classed under a marine and beach threat early yesterday but that was lifted later in the morning and punters were urged to be sensible and cautious in the ocean.

Mal Egginton from Tutukaka Surf said it was business as usual on the water yesterday morning, with a planned surf lesson for a group of international students going ahead at Sandy Bay.

"[My son] has been on the phone since 7am, we've checked with Civil Defence and they've said you're okay," Mr Egginton said.

There was a small swell at Sandy Bay yesterday - enough to learn on, he said.

Refinery NZ and Northport, at the entrance of Whangarei Harbour, were not evacuated but staff at both companies were monitoring the situation and keeping an eye on alerts.

A Northport spokesman said two ships at the port were delayed from sailing. One ship carrying logs, which was loaded and lashed, was due to go at 7am but it left at 11am.

The other ship was carrying laminated veneer lumber and was close to being completed so workers continued loading the ship when alerts came in.

All ships were told to put extra lines and rope to the jetty, the spokesman said.