A swarm of quakes - including a magnitude 6 and three at or above magnitude 5 - have hit Christchurch, toppling already damaged buildings, injuring 60 residents and disrupting power, phone services and retailers.
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The first quake - magnitude 5.8 quake, 8km deep and centred 20km north east of Lyttelton - struck at 1.58pm, GeoNet said. It was followed by a magnitude 5.3 quake at 2.06pm, a magnitude 6 quake - the largest - at 3.18pm and a 5.0, just 10 km deep, at 4.50pm.
The quakes were felt as far south as Queenstown and as far north as Lower Hutt, according to GeoNet. People in Greymouth, Ashburton, Dunedin, Hanmer Springs and Oamaru also felt them.
Orion chief executive Rob Jamieson said power had been restored to rural areas, including Springston and Dallington by 6pm. In New Brighton only about 5000 people were still without power, though the network remained fragile, particularly in the New Brighton area.
Jamieson said they were using back-up systems following damage at Transpower's Bromley substation.
"Therefore customers in the New Brighton area should prepare for a night without power whether they have a power supply at the moment or not."
Residents were asked to prepare for intermittent power supply over the next few days, he said.
Meanwhile, Civil Defence advised that sewage had flowed into the Avon River and people were asked to keep away from the waterway and estuary for 48 hours.
The city's treatment plants were working and there was no apparent damage to water infrastructure. The chief medical officer of health was not asking people to boil water at this stage.
A St John spokesman said ambulance communications had received up to 150 111 emergency calls since the first quake.
Staff had assessed and treated about 60 patients with minor quake-related injuries or issues, he said.
A police spokesman said Windsor House Rest Home residents in New Brighton were reported to be trapped on the second floor, but were being evacuated by the Fire Service.
The Coastguard rescued four people trapped at Boulder Bay near Godley Head.
One person was reported to have been injured at the Eastgate Shopping Centre and had been taken to Christchurch Hospital, the police spokesman said.
A woman at the Northlands Shopping Centre fell and injured her stomach, but did not require medical treatment.
'IT COULD HAVE BEEN WORSE'
Christchurch people have been spared "far, far nastier" injuries from today's quakes because the CBD remains empty from the early tremors.
Civil Defence controller David Coetzee said there were reports of 19 injuries, all of which were minor.
"This is very similar to the June event - significant ground shaking, shallow and they are large earthquakes so we can expect damage," Coetzee said.
"This is significant but the affects from an injury perspective could have been much worse. We're lucky actually that we had the CBD already cordoned and there weren't people in there."
There were unconfirmed reports of a building collapsed in the CBD, he said.
"It could have been far, far nastier, far more serious if there were people. It could have been far worse if that area was not vacated."
There was no expectation that there would be a formal state of emergency declared because local officials felt they could deal with things within existing resources.
Local officials were "pretty upbeat" despite the quakes, he said.
"They appreciate this could have been far, far worse and from that perspective, I think the morale is good. Obviously, at this time of the year, it's probably the worst time for something like this to happen and it will impact on all of us. We will just have to work through that again."
Reports on the impact of the quakes were still emerging, with council staff spreading across communities for "needs assessments".
It was already clear that some households were leaving and seeking alternative accommodation for the night because they did not feel safe.
There were reports of further damage to residential and commercial properties although the extent was not significant so the council had no intention of setting up welfare centres. But if people needed help, they should call the council, which would run an emergency operation centre over night to respond to any needs.
It was reasonable to expect there would be further damage to buildings, but it was too early to say the extent of it.
There were reports of new liquefaction and rockfalls and it was expected there would be further aftershocks.
Christchurch MP Lianne Dalziel said today's earthquakes were a terrible way to end the year and people are at the end of their tether.
"It is heart-breaking coming just two days before Christmas when people were just beginning to relax and were looking forward to a break."
The New Brighton police were fantastic and sprang into action immediately, she said.
"They will be providing reassurance to the eastern suburbs and ensuring that people and their properties are safe overnight, as will other emergency staff around the city."
CATHEDRAL ROSE WINDOW COMPLETELY COLLAPSED
The Christ Church Cathedral rose window has now completely collapsed and more damage is feared, Dean Peter Beck said.
"We don't know the rest of the damage. It was already very seriously damaged and it will be further damaged again," he said.
Beck said the new quakes were a "huge emotional shock".
"We were starting to get traction again and now it feels like June 3 again," he said.
The Christchurch Arts Centre has sustained minor damage.
Centre director Ken Franklin said a few gables had collapsed, but there was no "substantial damage that was obvious".
EMERGENCY SERVICES RESPOND
A partly demolished building and a vacant house have collapsed following today's quakes, police said.
There were still no reports of widespread damage or injury, but there had been significant rockfall at Redcliffs, police spokesman Stephen Hill said.
A stopbank on New Brighton Road had also collapsed, and there were reports of major holes on Broadhaven Ave and liquefaction in Avonside.
Earlier today, Hill said four people had to be rescued after they were trapped by a rockfall in Boulder Bay.
One person, who was at the Eastgate Mall in Linwood, had been injured and was taken to hospital.
The WINZ building in New Brighton had suffered some damage and staff had to be evacuated.
Many malls were closed and police patrolled streets for damage.
Roads were gridlocked as people tried to rush home, but police warned motorists to slow down and drive with care. Drivers were urged to stay away from the hill suburbs as there was a risk of further rockfalls.
The Lyttelton Tunnel remained open.
St John Ambulance responded to at least 19 people with various injuries. They included six people who collapsed, two people who had seizures, one person who had a panic attack, and one person who received a knock to their head, St John Regional Operations Manager Chris Haines said.
One person was also treated by St John after having a minor car accident.
Other injuries included chest pain and anxiety issues and six people were treated for "unknown issues", Haines said.
IMPACT ON INFRASTRUCTURE
The National Crisis Management Centre has been activated in response to the quakes.
Phone services were disrupted and about 26,000 Orion customers were without power in the eastern suburbs, including New Brighton and Dallington.
Power company Orion said it appeared the power was out due to tripping caused by shaking rather than damage to equipment. Crews were out assessing the damage.
Christchurch Airport has reopened and flights will resume at 6pm.
It was evacuated and flights cancelled after the first quake.
Fairfax reporter Hamish Rutherford, who was at the airport when the first quake struck, said alarms had sounded, people had left the building, and were waiting outside.
He said people kept calm while the building rocked from side to side during the first strong quake, which lasted about 20 seconds.
Christchurch Airport general manager Jim Boult said the runways and the terminal buildings were cleared of any damage late this afternoon.
Boult warned there would be considerable disruption to many flights. ''I think it will be well into tomorrow before we clear the backlog,'' he told Radio New Zealand.
A lot of people had left the airport in their cars to return to their homes to check on their loved ones and properties, he said.
Telecom said there had been no significant disruption to its services as a result of the quake.
But disruption to main power supplies meant that some equipment was operating on battery and generator backup.
Telecom was asking people to use texts rather than calling in order to ease the load on its mobile networks.
Emergency calling remains operational, it said.
BLOW TO RETAILERS
A visitor to the city said Westfield Mall was evacuated after the first shake. Terrified shoppers stumbled and fell as they fled the mall and items tumbled off shelves.
People shopping and working at the mall were almost in tears as they spoke of another Christmas marred by earthquakes.
Noelene Barron, who worked in the mall, said after the first quake that, while it was frightening, the worst thing was knowing that there were likely to be ongoing aftershocks now.
Central City Business Association manager Paul Lonsdale said the shakes came at the worst possible time for retailers, as people completed their Christmas shopping.
Ballantynes department store had closed for the day, even though it was brought up to 100 per cent of the earthquake code, after the February shake, he told Radio New Zealand.
"It's really the last thing we needed - a shake just before Christmas," he said.
"We've had a hell of a year really in many respects.
"We thought it was close to being over, but perhaps not quite."
Clinical psychologist Maureen Mooney said the quakes would have put people back on heightened awareness, as they struck just as they had thought the aftershocks were dying out.
It was not possible to say how the proximity of the quakes to Christmas would affect people, she said.
Some would take comfort in being with friends and family when the quakes struck, others would have been shaken by having them hit just as they were trying to relax for Christmas.
Canterbury Earthquake Recovery Authority head Roger Sutton was at home ready for the holidays when the first quake hit.
"I thought 'bugger'," he said.
"I've been at home checking on family. I'm running to work."
Sutton seemed agitated, saying he had been stuck in traffic and had yet to a get a briefing.
Christchurch Mayor Bob Parker was at Lake Taupo getting ready to celebrate Christmas with his family when the quake hit.
He said he was desperately trying to get back home and was expected to land in Christchurch after 7.30pm.
"I've been texting family members to see if everyone is okay, everyone is very shaken. I haven't heard any more significant problems at the moment.
"Inevitably it would have caused damaged to structures, we hope it hasn't unsettled any rock falls, and we just have to hope the liquefaction issues don't return."
Parker said he felt "really worried" and wanted to get home.
"The randomness of this sort of event is very unsettling for everybody."
Earthquake Recovery Minister Gerry Brownlee has cut short a family holiday just hours in to it, and is this afternoon headed for Christchurch to assess the damage.
Prime Minister John Key said he was being kept up to date on the latest quakes as information came in.
It would be "frightening and disheartening" for the people of Christchurch and Canterbury to be experiencing the strong quakes, particularly so close to the holiday season, he said.
"My heart goes out to the people of Christchurch and Canterbury at this time," Key said.
"However, residents can be confident that the authorities are onto the situation and government resources stand ready to assist wherever they are needed.
"The Government's resolve to work with the people of Christchurch and Canterbury to rebuild remains unchanged following today's two aftershocks," Key said.
Christchurch Central MP Nicky Wagner is not in Christchurch but said her she had spoken to her staff who reported liquefaction in the streets in the eastern part of the city.
Wagner was in Cheviot, North Canterbury, when the first quake struck but said she felt the shaking.
She called her office who told her the house of one of her staff that had been damaged in an earlier quake had suffered further.
"They're a bit nervous about going into it and liquefaction is coming up in the streets there, that's in the east."
Labour leader David Shearer said emotions would be raw in Christchurch and it was heartbreaking for the people there to have to go through more aftershocks.
"We are standing alongside them and will do everything we can to support the Government and local agencies in helping with the on-going recovery process."
The party's local MPs were already out helping constituents and their thoughts were with those affected, he said.
Green Party co-leader Russel Norman said the quakes today were an unwelcome intrusion for the people of Christchurch after a hard year.
However the people of Christchurch had shown great resilience and their human spirit was indomitable.
"We have seen this human spirit in the past and I have no doubt we will see it over the coming months."
The party was ready to do all it would to help people in Christchurch, he said.
RESIDENTS FRIGHTENED BY SWARM OF QUAKES
St Martins resident Jo Davis said she could hear sirens and was hoping there weren't injuries from the latest quakes.
"I was terrified, I guess just because it's been so long since we've had a decent one. We've had a TV and glasses fall over but no repeat of liquefaction like in June so I guess it's not so bad.
"There were four kids here since it's school holidays and the two-year-old in the sandpit was the least worried. The neighbours were screaming."
Staff and visitors at the Ferrymead Heritage Park clung to each other as the first quake hit and emptied shelves in the gift shop.
''It was horrible - not as bad as the February one but horrible just the same,'' a staff member said.
''We clung to each other - it seemed to go on for a long time.
''There was a noise but there were lots of noises - the quake and then everything falling off shelves.''
No major damage to the park or its buildings at the foot of the Port Hills was immediately apparent.
June Goodman, a Papanui retiree was waiting for a flight to Hamilton for a five day tour of the North Island when the first earthquake hit. She said while she had learned to cope with the quakes today's shake was clearly large.
"It was quite a ripple - I couldn't believe it. It was like a ripple going across the floor, that's how I felt it - some of them are a violent shake but that was more like a wave."
Anthony Surynt was working in an electrical workshop in Sydenham when the 1.58pm quake struck.
He said it was the biggest one he has felt since June 13, when a 6.3 magnitude hit the city.
He could see the Grand Chancellor from where he was and said it was still standing.
Nothing had fallen off the shelves but it was quite a scare as there hadn't been many large earthquakes in the area for a while, he said.
It lasted for about 10 to 15 seconds, but didn't have any sharp "vicious movements" like the previous quakes had caused.
Shirley resident Jenny Dalziel said the first quake was about 10 seconds long and shook things off shelves.
She said she was driving to her mother's house and had spotted liquefaction bubbling up in some areas though it did not appear as serious as previous quakes.
Vanya Rothwell, of Linwood, was at Eastgate with her daughter and grandson. They were in their car in the parking lot.
"It felt as if we were towing a trailer or had hit another car and then it started to really bounce the car."
They got out of the car when aftershocks hits. People were running out of the mall screaming, and children were crying, Rothwell says.
Last year, Christchurch was rocked by a series of earthquakes on Boxing Day, with more than two dozen recorded.
A 4.9-magnitude quake at 10.30am was the 17th most powerful since the damaging 7.1 quake on September 4.
The earthquake that caused the most damage hit on February 22, killing 182 people.