The National Emergency Management Agency issued a tsunami warning following a magnitude 8.1 quake off the Kermadec Islands, about 1000km north of the North Island, this morning.
The quake followed a 7.4 temblor in the same area, and a 7.1 quake off the North Island east coast early today.
Nema said coastal inundation was expected in parts of the North Island, and "strong and unusual currents and unpredictable surges" were expected in many other areas, including Otago and Southland. Nema said there was a threat to beach, harbour, estuary and small boat activities.
However, Nema downgraded the threat early this afternoon, saying that advice from GNS Science was that the largest waves had passed and residents who had evacuated could return home.
The Clutha District Council said though the tsunami threat had been reduced in the district, it still asked people to avoid the shore as there may be strong or unusual currents and unpredictable surges.
Thousands of North Island residents headed for higher ground following the initial tsunami warning.
Nema earlier said surges could affect the east and south coasts of the South Island from the Waipara River to the Rakaia River, including Christchurch and Banks Peninsula, and from the Taieri River to Puysegur Point, including Invercargill. Stewart Island could also be affected.
In a Facebook post this morning Emergency Management Southland said there could be a threat of strong currents and unpredictable surges near the shore.
''It is advised to stay off beaches and shore areas. Stay out of the water (sea, rivers and estuaries, this includes boats). Do not go sightseeing. Share this information with family, neighbours and friends.''
There was no requirement to evacuate, it said.
In an update this afternoon it said there was still a National Advisory in place for tsunami activity and people should expect strong and unusual currents and unpredictable surges at shore.
"Advice is to stay off beaches and shore areas."
Otago Civil Defence and Emergency Management said on social media it was good news that coastal Otago south of the Taieri was no longer under a coastal and marine warning.
"This morning's events are a good reminder for us all of what's needed if you're near the coast in the event of an earthquake -- if it's LONG or STRONG, get GONE."
Further south, Oreti Beach near Invercargill was quiet this morning, but a handful of people still visited despite the advice to stay clear of coastal areas.
One policeman in an unmarked car was seen by a reporter leaving the beach at about 11am.
People could also be seen walking the Te Araroa Trail.
French travellers Caroline Ly and Oaianne Lelay said they were aware of the tsunami threat but were not concerned as they felt far from any risk.
Ms Ly said she was informed of it by an Instagram post made by the Prime Minister earlier today.
However, Ms Lelay said she received information from Immigration New Zealand, and was then updated via social media.
The latest Nema update (updated at 1.54pm)
All people who evacuated can now return.
The advice remains, for all areas under Beach and Marine threat, to stay off beach and shore areas.
We expect New Zealand coastal areas to experience strong and unusual currents and unpredictable surges at the shore following a magnitude 8.1 earthquake near KERMADEC ISLANDS REGION at 2021-03-05 8:28 AM.
Strong currents and surges can injure and drown people. There is a danger to swimmers, surfers, people fishing, small boats and anyone in or near the water close to shore.
People in or near the sea in the following areas should move out of the water, off beaches and shore areas and away from harbours, rivers and estuaries.
AREAS UNDER THREAT:
The West Coast of the North Island from CAPE REINGA to AHIPARA,
the East Coast of the North Island from CAPE REINGA to MAHIA including Whangarei, GREAT BARRIER ISLAND, the East Coast of Auckland, Waiheke Island, Waitemata Harbour, Tauranga, Whakatane, Opotiki and Gisborne, the West Coast of the South Island from FAREWELL SPIT to MILFORD SOUND including Westport, Greymouth and Hokitika, and the CHATHAM ISLANDS.
There is no tsunami threat in all other areas.
ADVICE FOR PEOPLE IN AREAS UNDER THREAT:
STAY OFF THE BEACHES AND SHORE AREAS
Coastal inundation (flooding of land areas near the shore) is not expected as a result of this event. We are advising people to:
Move out of the water, off beaches and shore areas and away from harbours, rivers and estuaries.
Do not go to the coast to watch the unusual wave activity as there may be dangerous and unpredictable surges.
Listen to local civil defence authorities and follow any instructions.
Share this information with family, neighbours and friends
Return home if you have evacuated.
Strong and unusual currents and unpredictable surges will continue for several hours and the threat must be regarded as real until this Advisory is cancelled.
This National Advisory has been issued following an assessment of information available. The situation may change as new information becomes available. Listen to the radio or TV for updates, or check www.civildefence.govt.nz
- ODT Online/Daisy Hudson/Laura Smith
