2011 Christchurch Earthquake: NZ's Deadliest Since 1931

The 2011 Christchurch earthquake was a magnitude 6.2 earthquake that struck New Zealand’s second-largest city at 12:51 p.m. on 22 February 2011. Although smaller than many earthquakes, it was extremely shallow and close to the city centre, and it killed 185 people, making it the country’s deadliest natural disaster since the Hawke’s Bay earthquake of 1931. It destroyed much of the central business district and set off a reconstruction that lasted more than a decade.

Background: the Canterbury earthquake sequence

Christchurch, the main city of the Canterbury region on the South Island, was not considered one of New Zealand’s highest-risk areas. That changed on 4 September 2010, when a magnitude 7.1 earthquake struck near Darfield, about 40 kilometres west of the city. It damaged thousands of buildings but, striking at 4:35 a.m., killed no one directly.

Thousands of aftershocks followed. The February 2011 earthquake is regarded as one of them, but it ruptured a separate, previously unmapped fault beneath the Port Hills on the city’s south-eastern edge, only about 5 kilometres below ground.

The earthquake of 22 February

The epicentre lay near Lyttelton, roughly 6-10 kilometres from the city centre, at lunchtime on a working day when the centre was busy. Ground shaking was exceptionally violent: instruments recorded vertical accelerations of more than twice the force of gravity close to the epicentre, among the highest ever measured.

Two multi-storey office buildings collapsed. The six-storey Canterbury Television (CTV) building fell and caught fire, killing 115 people, including many international students at a language school on its upper floors from Japan, China, the Philippines and other countries. The Pyne Gould Corporation (PGC) building collapsed, killing 18. Falling facades and parapets killed others in the streets, including passengers on two city buses crushed in Colombo Street.

The spire of the Anglican Christ Church Cathedral, the symbol of the city, collapsed into Cathedral Square. Rockfalls and cliff collapses hit the Port Hills suburbs, and widespread liquefaction turned eastern suburbs into fields of grey silt and water.

Rescue and emergency

Rescuers from New Zealand were joined by urban search-and-rescue teams from Australia, Japan, the United States, the United Kingdom, Taiwan, China and Singapore. On 23 February the government of Prime Minister John Key declared a national state of emergency, the first in New Zealand’s history; it remained in place until 30 April 2011. Mayor Bob Parker led the city’s response. Less than three weeks later, on 11 March, the Tohoku earthquake and tsunami struck Japan, a country that had sent rescuers to Christchurch and lost 28 of its citizens, most of them students, in the CTV building.

The central city was sealed off behind a cordon, the “red zone”, which was not fully lifted until June 2013. Strong aftershocks on 13 June and 23 December 2011 caused further damage.

Investigation and blame

A Royal Commission of Inquiry examined why buildings failed. In 2012 it found that the CTV building, designed and built in the 1980s, had serious design deficiencies and should not have been approved. The findings led to tighter rules on earthquake-prone buildings across New Zealand, requiring owners to assess and strengthen older structures. Police later decided in 2017 not to bring criminal charges over the CTV collapse.

Rebuilding Christchurch

The government created the Canterbury Earthquake Recovery Authority (CERA) in 2011 with wide powers to lead recovery. More than 1,000 central city buildings, a large share of the centre, were eventually demolished. A temporary shopping area built from shipping containers, Re:START, became a symbol of resilience, and a “Cardboard Cathedral” designed by the Japanese architect Shigeru Ban opened in 2013.

In the eastern suburbs, land damage was so severe that the government offered to buy out about 8,000 homes in a residential red zone along the Avon River, much of which has since been turned into parkland. The total cost of the earthquake sequence was estimated at about 40 billion New Zealand dollars, an enormous sum for a country of about 4.4 million people, much of it covered by insurers and the state Earthquake Commission.

By the numbers

Timeline

• 2010, 4 September: The magnitude 7.1 Darfield earthquake damages Christchurch without direct deaths.
• 2011, 22 February: The magnitude 6.2 earthquake strikes at 12:51 p.m., killing 185.
• 2011, 23 February: New Zealand declares its first national state of emergency.
• 2011, 30 April: The national state of emergency ends.
• 2011, 13 June: Strong aftershocks cause further damage.
• 2012, December: The Royal Commission reports on the CTV building collapse.
• 2013, June: The central city cordon is lifted.

Why it matters

The Christchurch earthquake showed that a moderate earthquake directly beneath a city can be devastating, and that soft ground and old buildings magnify the danger, a lesson also drawn from the Kobe earthquake of 1995. It transformed New Zealand’s building regulations and left a rebuilt city centre that is very different from the one that existed before 2011.