Have you been affected by the quake?
Send us your photos and video.
Christchurch Mayor Bob Parker is thankful there has been no loss of life but there had been considerable damage across the city and outlying areas.
The city has been left devastated after a massive 7.1 magnitude earthquake struck 30km west of the city at 4.35am this morning.
The quake was at a depth of 33km and was centred near Darfield, and has left large parts of the area without power, water or telephones.
Mr Parker said he did not want to overstate the level of damage "but I think it's like an iceberg. There is, in a sense, below the visible line significant structural damage."
"There would not be a house or a family in our city that has not in some way had damage done to their person and or their property," Mr Parker said.
"Our thoughts are with our people.
"We know that a lot of people will be very nervous, deeply disturbed."
Scientists have described this morning's earthquake as the most significant since the 1931 magnitude 7.8 Hawke's Bay earthquake.
Mr Parker said electricity was being slowly restored to the city but there were still concerns about the situation with water and waste water.
Mr Parker said the inner city was being closed down, city residents are being asked to save water and not flush the toilet, not to go to "rubbernecking", and check on their neighbours.
Mr Parker said the worst problems seem to be centred in the city's eastern suburbs and rural areas in outlying Christchurch.
State of emergency
Civil Defence declared a state of emergency around 10am this morning.
New Brighton and other seaside areas are bracing for possible evacuation.
Prime Minister John Key has travelled to the area.
Christchurch Hospital inundated
Christchurch Hospital siad two men have been seriously injured by the earthquake.
One man in his 50s is in a serious condition in intensive care at Christchurch Hospital after a chimney collapsed on him.
Another man, also in his 50s, was seriously injured by falling glass.
The main Christchurch Hospital is being inundated by residents arriving with broken limbs, bruises and cuts.
A spokeswoman, Michelle Hider, asked residents with minor injuries to go to 24-hour surgeries for treatment rather than the hospital.
Christchurch Airport closed
All flights to Christchurch have been cancelled until at least 1pm. All flights from Auckland to Christchurch once flights resume are booked out.
Residents desperate for emergency supplies
Panicked residents have been queuing to buy water as uncertainty surrounds the stricken city's water supply.
But many businesses are unable to open their doors as the massive cleanup gets underway.
Nigel Bond, owner of the New World on Colombo Mall says he could barely see the floor of the supermarket this morning for stock, much of it now unusable. His staff have been working to clean up damaged stock since 5.30am.
"Unfortunately our big water shelf has collapsed and most of that stock has been lost," he told nzherald.co.nz.
"There's a bit of structural damage, like cracks in the floor and fallen ceiling tiles. Nearly everything's on the floor. Red wine, olive oil, you name it - it's not pretty."
Buildings, roads devastated across Christchurch
Street surfaces have risen up into a peak in the middle of a Christchurch road, while craters in the road have filled with water from ruptured mains. People in vehicles are trying to avoid them.
Among the affected streets are Hills Rd in Shirley and others in the suburb of St Albans and New Brighton.
In other areas roads have been blocked by debris after several buildings collapsed onto the streets, leaving their interiors visible and the central city resembling a war zone.
Large groups of onlookers have gathered to survey the damage and take pictures with their cameras and mobile phones.
Several large aftershocks have already struck the region, and wardens dressed in high-visibility gear are asking people to stay well clear of buildings because of the high risk of further collapses.
The city centre is now officially closed.
Traffic lights are still not working in several places around the central city, creating gridlock as the traffic flow increases.
Mayor ask residents to conserve water
Mayor Bob Parker has asked residents to conserve water.
Mr Parker has warned residents not to flush the toilet and to conserve water. There are fears the sewerage system has been damaged.
Engineers have been checking the city's priority infrastructure.
Mr Parker urged Cantabrians affected by the earthquake to check on their neighbours to ensure they were safe.
Personal accounts: Residents 'lucky to be alive'
Marsha Witehira, 30, was rescued by friend Tama Wharepapa, who literally pulled her to safety by her feet as a wall in her bedroom collapsed around her.
"It just missed my head," Ms Witehira said. "I'm very lucky to be alive. If Tama wasn't here to wake me from my sleep and pull me out, I really wouldn't like to think what the result would be."
Knee Doherty was asleep in her central Christchurch home when the building next door collapsed.
"We didn't even notice the movement as much as the noise," she said. "The back of the house is pretty much gone. All the house next door is gone. It was just a massive noise."
'A scary sight to see'
New Zealand Herald reporter Jarrod Booker,who lives in the central Christchurch suburb of Linwood, said he was woken by "extremely violent shaking."
He said the chimney from his next door neighbour's house had fallen and smashed through a car's windscreen.
"There have been a number of aftershocks of a much lesser degree since then."
Mr Booker's partner, Kineta Knight, said it was a scary sight to see.
"The scariest thing was the quake just felt like it would never end. It wasn't a sharp, sudden jolt. It was like being on a rollercoaster.
"Things were smashing everywhere, we could hear glass breaking."
Newstalk ZB reporter Craig Kerr spoke to Auckland host Pat Brittenden from the Christchurch office, which he said had sustained damage.
"Basically, the place is destroyed. Desks that were standing up are flattened against the ground. The filing cabinets are tipped over. The lifts in the building are obviously out of action."
"The building just along the road from us here has been flattened - it's on the ground," he said.
A Timaru resident told NZPA he was awakened by the shaking. His house was groaning and a bedside lamp crashed off its table.
- NZ HERALD STAFF / NZPA