22 February 2011
At 12:51pm on February the 22nd 2011 a magnitude 6.3 earthquake slammed into Christchurch bringing the city to its knees.
This was to be the most devastating in a series of damaging aftershocks following Canterbury’s 4th September 2010 earthquake, also known as the Christchurch or Darfield earthquake, which had struck the South Island of New Zealand with a magnitude of 7.1, shaking people from their slumber in the early hours of the morning at 4:35 am.
Miraculously there were no deaths from the 4 September main event and only 2 injuries (one from a falling chimney and a second by flying glass), with most residents off the streets and in the relative safety of their homes.
But on 22 February 2011 that luck ran out.
By comparison the February earthquake struck just after midday on a weekday, while people were out and about, and caused the death of 185 people with 164 serious injuries.
There was significantly more damage to buildings and infrastructure in the February quake. As although smaller in magnitude than the September shake, February’s quake epicentre was only 10km south-east of the city and at a shallow 5km deep. The peak ground acceleration, which measures the intensity of an earthquake rather than the magnitude (energy released), was extremely high and it shook the ground beneath the city’s feet hard. The simultaneous horizontal movement of the earthquake coupled with this intense accelerated vertical movement made it ‘almost impossible’ for some buildings to survive.
Most of the damage occurred to older buildings, particularly those with unreinforced masonry and built before stringent earthquake codes were introduced in New Zealand. This included earthquake resistant design incorporated into building codes after lessons learnt from the 1931 Napier Earthquake and added requirements from the 1960’s.
Although comparatively modern the six-story Canterbury Television (CTV) building collapsed with the death of 115. As did the four-storey Pyne Gould Guinness (PGC) with 18 casualties. And eight were killed when masonry fell in a central city main thoroughfare, Colombo Street and crushed Red Bus number 702.
Rescue efforts continued for over a week with more than 600 emergency workers from six countries who helped in the search for quake survivors, with the last survivor pulled from the rubble the day after the quake.
Hampering rescue efforts was the major damage to roads and bridges as well as liquefaction and surface flooding. “Road surfaces were forced up by liquefaction, and water and sand were spewing out of cracks.” (Wikipedia).
This liquefaction caused significant ground movement, undermining many foundations and destroying infrastructure. More than 400,000 tonnes of silt made its way to the surface which ‘may be the greatest ever recorded anywhere in a modern city’ and needed to be cleared. Even after the liquefaction was removed by the truckload, the remnants would bake in the summer February sun and blow as clouds of eye-stinging dust down city and suburban streets.
It was to be a year long swarm of shakes for quake-weary Cantabrians, including a large aftershock (6.3) in June 2011 and a series in December 2011, the largest (4.9) on Boxing Day.
In April 2013 the Government estimated that the total cost of the rebuild would be as much as $40 billion, up from an earlier estimate of $30 billion – ranking the earthquake as the world's fifth most costly to insurers. Some economists have estimated it will take the New Zealand economy 50 to 100 years to completely recover.
Despite it all, Cantabrians have been remarkably resilient and remain positive with their hearts set on seeing Christchurch city rebuilt. There are numerous anchor projects in the pipeline with the City Council's ‘Christchurch Central Recovery Plan.’ This includes the Convention Centre, the Town Hall restoration and the Metro Sports Centre, as well as many Arts, Cultural, Innovation, Health and Retail Precincts which it is hoped will breathe life back into this decimated city.