A 7.7 earthquake struck near the Loyalty Islands,near New Caledonia just before 3pm.
The National Emergency Management Agency is urging people on boats and at marinas to move ashore.
Strong and unusual currents could hit both sides of the North Island from Cape Reinga to Whanganui on the west coast - and to Tolaga Bay on the east coast.
The South Island's West Coast could also be under threat, between Farewell Spit and Milford Sound.
