Re: Mag. 7.8 Earthquake off New Zealand
Southland hit by repeated earthquakes
Last updated 13:29 16/07/2009
Fiordland Advocate
The first, a 6.1-magnitude quake, struck at 9.41pm, Wednesday. It has been followed today by a magnitude 5.9 shake at 1.50am, a magnitude 5.3 at 12.24pm and a magnitude 5.5 at 12.44pm.
They follow the main 7.8-magnitude quake, which struck at 9.22pm, Wednesday, centred 100km northwest of Tuatapere with a focal depth of 12km.
The most recent aftershock this afternoon was felt in Central Otago and Southland, according to the Geonet website.
GNS technician Matthew Stevens said all four aftershocks were shallow at only 5km deep. "They would have been felt quite strongly at the surface," he said.
Geonet spokesman Kevin Fenaughty said there had been hundreds of minor shakes, but only major aftershocks - the ones people would have felt - were being recorded on the agency's website.
There had been about 200 reports from people who had felt the main earthquake last night, and those reports would be used to paint a picture of its overall reach and effect, Mr Fenaughty said.
Meanwhile, Despite the near-record magnitude of last night's earthquake in Fiordland, the Insurance Council says few claims have been lodged.
Insurance Council of New Zealand chief executive Chris Ryan said he was not expecting a lot to come.
The nature of the earthquake that hit, which has been described as a rolling motion, instead of sharp jolts, meant minimal damage might be reported, he said.
"From our point of view we'd be strongly encouraging people to check their properties, especially their chimneys."
CHECK-UP OPERATION
The earthquake caused a small number of slips on steep Fiordland mountainsides.
Southland Civil Defence Group Controller Neil Cruickshank said that his team flew over the epicentre of the quake searching for damage, but found little.
Civil Defence officers and Conservation Department staff started checks early this morning for possible damage in Southland and Fiordland following the earthquake.
The Department of Conservation is continuing to check its huts and tracks, and the Southland District Council and the Transport Agency have been assessing roads and bridges for possible damage, but there are no reported problems.
"We have over 1200 structures in Fiordland National Park alone and we urge the public to let us know immediately if damage has occurred to any of them," DOC acting Te Anau area manager Andrew Cudby said.
Mr Cudby described the earthquake as "a long rolling motion, a bit like being on the sea."
Neil Cruickshank said last night'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 said there were no reports of substantial damage in the Milford and Te Anau areas.
Mr Cruickshank said that, while there had been disruption to electricity supplies, power companies had reported no major problems, and the rail network was reported to be undamaged. "Telephone services are operational," he said.
TSUNAMI ALERT
The earthquake was about the same magnitude as the killer quake that devastated the Sichuan region of China in May 2008, leaving at least 68,000 people dead. It was also the same magnitude as the 1931 Napier earthquake, which caused the largest loss of life and most extensive damage of any quake in New Zealand's recorded history with 256 dead.
Soon after the quake hit, the
Pacific Tsunami Warning Centre issued an advisory, which extended across the Tasman with Sydney and Australia's south-east coast put on alert.
The Sydney Morning Herald website reported last night that residents had been warned to keep away from the water's edge and a Sydney a performance at the Bondi Pavilion was cancelled and all theatregoers evacuated from the beachfront venue.
Mr Cruickshank said a 17cm wave had been detected at Jackson Bay on the West Coast and the tsunami warning had subsequently been cancelled.
In Doubtful Sound, the manager of the Deep Cove Hostel and his wife said the quake was so severe they hid under a table.
He had reported loud bangs in the area, which might indicate slips, and had heard water "swooshing loudly" in the sound.
The Southland Civil Defence Emergency Management Group activated the region's emergency operations centre to assess damage reports.
Te Anau helicopter pilot Mark Deaker said he saw power lines arcing and sparks flying in the air.
An Invercargill man said the initial 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.
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.
GNS Science geologist Bill Fry said scientists worked into the night to gather enough details on the site of the quakes to be able to assess any continuing risks to people or property.
"The shallower an earthquake is, the more shaking there's going to be ? and this was quite shallow," he said.
Prime Minister John Key told a crowd of about 200 people in Invercargill today that he was in Christchurch last night when the earthquake hit and the earth did not move for him - nor his wife - despite the children being overseas.
Mr Key said he was happy to visit quake-affected areas if required.
"If there is significant damage or something that I can usefully be deployed to I will certainly go and have a look and lend a hand," Mr Key told Radio New Zealand.
Any government response would depend on damage which had yet to be assessed.
"All the feedback we've had so far is while it's been a large quake, certainly at this point no reported loss of life which is fantastic, and no great reports of damage."
NEW ZEALAND'S BIGGEST EARTHQUAKES
Notable New Zealand earthquakes of modern times include the 6.8 magnitude Gisborne quake of December 20, 2007, which was offshore but caused buildings to collapse in the Gisborne CBD, and 20 years before, Edgecumbe's 6.5 quake on March 2, 1987, which was very destructive because of its shallowness.
The top quakes recorded in this country are:
* 8.2, Wairarapa, January 23, 1855 - The most severe earthquake to have happened in New Zealand since systematic European colonisation began in 1840.
* 7.8, Fiordland, July 15, 2009 - only 12km deep and on the coastline near Milford.
* 7.8, Napier, February 3, 1931 - The 1931 Hawke's Bay earthquake caused the largest loss of life and most extensive damage of any recorded NZ quake.
* 7.8, Murchison, June 17, 1929 - The massive rumbling of the 1929 Buller earthquake was heard as far away as New Plymouth.
* 7.6, Pahiatua, March 5, 1934 - Also known as the Horoeka earthquake, it shook the lower North Island and was felt as far away as Auckland and Dunedin.
* 7.5, Marlborough, October 16, 1848 - This was the largest in a cluster of earthquakes that hit central NZ that year.
*7.5, Cape Farewell, October 19, 1868 - There were reports of conspicuous and extensive ground cracking as well as damage to houses the Collingwood, Pakawau and Farewell Spit.
*7.5, Hawke's Bay, February 23,1863 - Centred near Waipukurau, reports from the time said there were numerous landslides, liquefaction, and surface faulting. Many chimneys were also damaged in Napier.
*7.3, Hawke's Bay, February 13, 1931 - Striking Hawke's Bay 10 days after it was devastated by an earlier quake, it was said to be felt as far away as Hamilton and Christchurch. It was described by some inland communities as even more violent than the February 3 shock.
*7.3, North Canterbury, September 1, 1888 - the Amuri District was shaken by a large earthquake with severe intensities of ground-shaking
*7.3, Auckland Islands, September 30, 2007 - Felt in the lower South Island.
* 7.2, Wairarapa I, June 24, 1942 - This earthquake severely rocked the lower North Island during World War 2, causing extensive damage to local buildings.
*7.2, Puysegur Trench, November 22, 2004.
*7.1, Arthur's Pass, March 9, 1929 - The earthquake struck the small, isolated communities of Arthur's Pass and Otira, toppling chimneys and throwing furniture. The earthquake was felt throughout the South Island and as far north as Taranaki and Napier in the North Island.
* 7.1, Inangahua, May 24, 1968 - The Inangahua earthquake killed three people and was felt over much of the country.
*7.1, Fiordland, August 22, 2003 - Described as one of the largest "on-land" earthquakes in New Zealand at the time for many years it was felt strongly in Te Anau, where there were reports of goods shaken off shelves. Many people in the southern half of the South Island were woken by the shaking.
* 7.0, Wairarapa II, August 2, 1942 - The shock that struck on August 2 was nearly as severe as the disastrous June 24 earthquake five weeks earlier.
*7.0, East Cape, February 6 1995.
Source - GNS Science
- By SAM McKNIGHT, SHANE COWLISHAW, Southland Times, NZPA and Fairfax
http://www.stuff.co.nz/national/2598128/Magnitude-7-8-quake-hits-Southland
