A tsunami warning was issued tonight after a major earthquake measuring 7.8 struck Fiordland, followed by a large aftershock.
LATEST: GNS Science reported the first quake struck at 9.22pm, centred 100km southwest of Te Anau and was 12 kilometres deep. It was initially reported as measuring 6.6 on the Richter scale but this was later upgraded to 7.8 on the Richter scale. It was felt strongly by residents in Invercargill, Dunedin, Timaru and as far north as Wellington.
An aftershock measuring 6.1 and five kilometres deep struck around 150 km west of Tuatapere at 9.41pm, according to GNS Science. It was also felt in Wellington.
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 tonight's big Fiordland earthquake.
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 Bluff. "We're just waiting on confirmation of that, and we will cancel the warning for a potential tsunami," he said.
The Hawaii centre cancelled its alert just before 11pm.
The Southland Civil Defence Emergency Management Group activated the region's emergency operations centre to assess damage reports.
CDEM Group Controller Neil Cruickshank said it was believed the epicentre was a considerable distance from any township.
The Deep Cove Hostel manager and his wife, who are based at Doubtful Sound, said the quake was so severe they hid under a table.
The manager reported loud bangs in the area which might indicate slips and he heard water "swooshing loudly" in the sound.
An Invercargill man said his flat started shaking and he jumped under a table for safety. ''I was crapping myself,'' he said.
Another woman in the city said her children started screaming.
''We just told them it was like a ride.''
In Tuatapere, a Waiau Hotel patron said a ute parked outside the street shaked as though someone was jumping on it. ''The staff ran away scared so the drinks have been free.''
An Invercargill man said the first quake lasted at least 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.
Te Anau helicopter pilot Mark Deaker said he saw power lines arcing and sparks were flying in the air.
Fresh Choice supermarket owner Keith Cullen said 10 to 20 items smashed in each aisle of the supermarket.
Civil Defence officials said they were concerned by varying measurements of the first larger quake in Fiordland tonight and had issued a ''potential tsunami'' warning in Southland.
"We've had big differences in the measurements of the quake, ranging from 6.6 by GNS Science, to 8.2 by a tsunami warning centre in Hawaii - we're issuing a precautionary message," said an emergency management spokesman in Wellington, Vince Cholewa.
Mr Cholewa said the initial United States Geological Survey measurement used by the Hawaii tsunami centre was quickly downgraded to 7.8 magnitude. ''GNS and the USGS are working through it.''
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 jolt.
Neither the Manapouri Power Station and Tiwai Point Aluminium Smelter reported any damage.
A Queenstown resident living in a three-storey apartment said the building shook and swayed. ''Holy crap that was significant,'' the resident said.
The Pacific Tsunami Warning Centre in Hawaii issued the warning soon after the quake struck.
The centre said it was not known if a tsunami was generated, but it was issuing the warning based on the earthquake evaluation.
''An earthquake of this size has the potential to generate a destructive tsunami that can strike coastlines in the region near the epicentre within minutes to hours,'' it said.
A magnitude 6.7 earthquake which struck Fiordland at 1.29am on October 16, 2007 _ 60km west of Milford Sound at a depth of 24km - was the most recent previous big shake in the area.
But one of New Zealand's biggest quakes - a magnitude 7.2 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.
The first aftershock from tonight's quake was measured 19 minutes later, at 9.41pm by GNS Science. It was 6.1 magnitude shake at 5km depth 150km west of Tuatapere.
Aftershocks occur as the earth's crust adjusts to stresses caused by the main shock, and no two aftershock sequences are exactly the same.
- NZPA and Fairfax
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