Christchurch has woken to a scene of utter devastation this morning, with some 300 people missing following the horrific earthquake at lunchtime yesterday.

The death toll has hit 55 identified bodies, according to Mayor Bob Parker today, with another 20 bodies found but not yet identified. Authorities warn it will rise significantly. The first Australian casualty was announced this morning, a male Australian resident of New Zealand origin. Grave concerns are held for another for Australians, says PM Gillard.

We will be updating this breaking story throughout the morning as news comes to hand.

Update 3pm Rescue attempts have been stopped on the CTV building, with police saying there is “no chance of survivability” for those trapped in the building and it’s too dangerous to continue with the precarious Grand Chancellor hotel so close. A group of Japanese students is believed to be inside the building, amongst others.

There are worries that if the Grand Chancellor collapses, it will trigger other buildings collapsing as well. Three hundred people remain missing.

Queues have formed for locals attempting to get petrol or buy essentials at supermarkets. An incredible photo gallery of images from the last day can be found at The Atlantic.

12.30pm Another person has just been rescued from the collapsed Pyne Gould building. Earlier reports that it was Anne Voss, the Australian woman trapped under her desk, were false. Hundreds still remain trapped in buildings.

12.00pm Grave concerns are held for the Grand Chancellor hotel, a 26-storey building that is one of the highest in Christchurch. News website stuff.co.nz tweeted:

“Police cordoned four-block radius around the Hotel Grand Chancellor, which is sagging badly and appears to be on the brink of collapse”

Then a short time after:

“Hotel Grand Chancellor in Manchester St had moved about one metre horizontally during the past 10 to 15 minutes”

Thankfully, no one is believed to be in the building. An eyewitness tweeted that it was “noticeably sagging.” A photo from Sunrise — Kochie was there, noting how its collapse seemed imminent — shows a before and after of the building.

Remarkable CCTV footage has emerged of a Christchurch supermarket at the moment the earthquake hit.

10.45am Earlier reports that 15 people have been found alive and well in the Canterbury TV building are false, says a fire-fighter at the scene, but rescuers are continuing to try and search for survivors. However,

On 2GB Ben Fordham spoke to office worker from Geelong Anne Vos, who remains trapped under her Christchurch office desk, bleeding, with no light apart from her mobile. Anne says she can hear other workmates yelling and rumours that rescuers are on their way.

This photo, posted by 3AW on Twitter, shows the sheer joy of two men getting rescued.

A Melbourne doctor, in Christchurch for a conference, volunteered her skills to help the injured yesterday. She told ABC radio: “[There were] a lot of broken legs… We were getting splints and pieces of wood, picture frames, anything that we could from the stores surrounding the cathedral in order to try and splint their legs up.”

An interactive photo gallery comparing the streets and buildings before and after the quake makes it easier for those not familiar with Christchurch to understand the destruction.

Google quickly created a clever crisis response site, which shows constant news updates, videos, maps, emergency phone numbers and information. It also includes a ‘person finder’, where people can either look for someone or note that they have information about someone, keeping a constant live feed update on those that are missing.

10am: PM Key declared a state of national emergency, announcing that yesterday’s quake will be regarded by the government as a separate event to last year’s one. He also reiterated that the whole nation of New Zealand was supporting Christchurch through this tragedy: “Today I want Christchurch to hear this message: you will get through this. This proud country’s right behind you and we are backing you with all our might.”

Early reports say rebuilding may cost NZ $16 billion.

While not as gut-wrenching as the earlier account by The Press’s music critic, this personal blog post shows what it was like being in the suburbs of Christchurch during the quake, where supermarkets closed and earthquake noise sounded like a freight train driving through the house.

So the morning of the earthquake we were all going to be in town – she getting her passport renewed, 3 others to go around and do tourist things (like visit the cathedral), and I was going to take my mom around the tourist shops to get presents for my niece and nephews. Lucky for us, it was rainy in the morning and we were being very lazy. My brother wanted a sandwich before we left, so everyone had some lunch and we played a game of scrabble. Just as we were pondering to go into town the earthquake hit

Reports three people have been pulled alive from the Pyne Gould Corporation building today, though some 50 others remain trapped — and apparently alive — there.

9am: PM John Key said yesterday that “we may be witnessing New Zealand’s darkest day”, and undoubtedly much of the news was extremely tragic. The temporary morgue being used to house earthquake victims’ bodies has been move “for capacity reasons”. Police announced the gruesome detail that they have had to amputate limbs in order to rescue some people. There was a mother who died cradling her injured baby in her arms. A nine-month-old died when a television fell on him during the quake. Huge numbers of workers remain trapped in office buildings throughout the CBD, with grave fears for their safety. A NZ photo gallery surveys the devastated CBD.

Local newspapers reported this morning “cries from the rubble” with “hundreds feared dead”…

Journalists at Fairfax-owned The Press newspaper in Christchurch had their own building collapse, but set up a temporary newsroom at their printing plant. Music critic Vicki Anderson writes a compelling account of what the quake was like:

With no warning the earth roared and shook us ferociously. Like my colleagues in the features department of Christchurch newspaper The Press, I dived under my desk.

I’m a music critic and as we shook and my mind’s eye flashed images of my four children I was pelted with CDs including, ironically, an Underworld album. The same thing happened to me on September 4, I was even hit by the exact same CD, but this was completely different and a much more visceral and potently deadly quake.

Halfway through the 6.3 quake I wanted to see if my colleagues were OK so stupidly stuck my head out from under my desk only to be hit by a piece of roof. I said “F**k!” at the top of my lungs and it was drowned out by the sound of our building falling down around us.

Across the room from under their desk someone was yelling “yahoo” like it was a fun ride. I was certain we were all going to die. Things seemed to be happening slowly but quickly at the same time.

Schools are closed around the Christchurch district today after thousands spent last night sleeping in emergency refuge centres set up in parks and halls. Power remains cut around most of the city, although energy company Orion hopes two-thirds of the city will have power by the end of today. Christchurch Airport is expected to open for domestic flights this morning. TVNZ has a compelling blog with updates every few minutes of the latest earthquake news.

For a comparison of how this 6.3 magnitude earthquake rates, check out this interactive earthquake map showing quakes around the globe.

Experts argue this was technically an aftershock of the bigger — but less damaging and deadly — earthquake in Christchurch back in December. Scientist David Rothery, from the Open University’s volcano dynamics group, told The Guardian:

“The magnitude 6.3 earthquake was a very large aftershock following the 3 September magnitude 7.0 earthquake. Its focus was at a very shallow depth of about 5km, which doubtless contributed to the severity of the ground shaking that witnesses in Christchurch describe as more severe than in September. The rupture was also much closer to the city, and this too made it worse. Other, hopefully smaller, aftershocks are to be expected. These will be a hazard to people trapped in damaged and weakened buildings and their rescuers.”

This photo from @senaz on Twitter shows the the iconic Christchurch Cathedral reduced to rubble.

As more aftershocks hit the city, and emergency services attempt to rescue those trapped, today will be another dark day for Christchurch.

To donate to the Red Cross Christchurch 2011 Earthquake Appeal, head here (if that link isn’t working, try this one).