The Pacific tsunami warning centre has cancelled its tsunami warning for New Zealand, while Civil Defence authorities said only a small wave was generated by Wednesday night's big Fiordland earthquake.
GNS Science upgraded its reading on Wednesday night for the quake to 7.8 magnitude, bringing it into line with international readings.
It struck at 9.22pm, centred in Fiordland, and was felt widely throughout the South Island and as far north as Taranaki. No major damage was reported, though there were some power outages in the south.
An aftershock measuring 6.1 hit 20 minutes later.
An emergency management spokesman in Wellington, Vince Cholewa,
said initial reports indicated a wave, around the 17cm height
predicted by the Hawaii warning centre, arrived about 10.30pm in
The Hawaii centre cancelled its alert just before 11pm.
GNS Science initially graded the quake as 6.6, contrasting with an estimate of 7.8 by the Pacific tsunami warning centre in Hawaii, but later upgraded it.
The quake was followed by a aftershock of 6.1 magnitude 20 minutes later.
Because of the size of the quake, and an initial reading in Hawaii of an 8.2 magnitude, Civil Defence issued a precautionary tsunami alert for Southland.
The Southland Civil Defence Emergency Management Group activated the region's emergency operations centre to assess damage reports.
Group Controller Neil Cruickshank said that the emergency
operations centre was monitoring the situation in Bluff, through
people and recording equipment based there.
A tsunami warning had been issued and Southland Civil Defence Emergency Management had monitored sea levels through people and equipment stationed at Bluff.
A 17cm wave had been detected at Jackson Bay on the West Coast and the tsunami warning had subsequently been cancelled, he said.
An Invercargill man said the initial quake lasted at east a minute.
"Things just started to rattle a bit, then the house started to sway."
He and his wife got their three young children out of bed and huddled under the dining table to wait it out.
Cracks had appeared around several door frames, he said.
Central Southland man Warren MacPherson said a hanging light in his house would have been swaying "a good six inches each way".
He was on the phone when the quake struck and rushed outside.
"By geez, there was a fair bit of movement," he said.
Invercargill police Inspector Olaf Jensen said there were no immediate reports of damage in the southern city, but the quake was significant enough to send staff into doorways.
He described it was a strong, rolling quake rather than a sharp
Cruickshank said tonight's earthquake gave the Southland region "a good shake" but was not particularly damaging.
"Invercargill reports that phone services were down in east Invercargill and power was out for some time in the suburb of Otatara because of the earthquake," he said.
"Southland District Council reports that in the Milford and Te
Anau areas there were no reports of substantial damage and the
infrastructure in those areas appears to be working well.
Inquiries are continuing to assess damage around the Tuatapere
Cruickshank said that in the morning Environment Southland staff, in co-operation with other agencies, would begin air reconnaissance in the morning to check for landslides in Fiordland.
The region's substantial roading network, particularly state
highways and bridges, and remote DOC huts would also be checked as
One of New Zealand's biggest quakes, a magnitude 7.1 tremor, hit Fiordland near Secretary Island off the Fiordland coast on August 22, 2003. It caused significant landslides in parts of the region.
Scientists recorded about 5000 aftershocks over several months in the wake of the 2003 quake.
Aftershocks occur as the earth's crust adjusts to stresses caused by the main shock, and no two aftershock sequences are exactly the same.
More than 14,000 earthquakes are recorded in New Zealand annually, but only about 20 are stronger than 5 on the Richter scale.
The Inangahua earthquake on the West Coast in 1968 measured 7.1 on the Richter scale and killed three people.
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