Background to the earthquakes
The first, and largest magnitude, earthquake occurred on 4 September 2010. Its magnitude – 7.1 on the Richter Scale – put it in the class of a major earthquake likely to cause serious damage. And it did.
The earthquake was centred 30km west of Christchurch at a depth of 10km. When it hit it buckled land, caused extensive liquefaction, toppled chimneys and did serious damage to homes and infrastructure. Thankfully, there was no loss of life, mainly because of the time it hit – 4.35am on a Saturday morning.
Many large aftershocks followed, including a 4.9 on Boxing Day 2010.
Then, just as Cantabrians were adjusting to the ‘new normal’, a magnitude 6.3 earthquake hit – just before 1pm on Tuesday, 22 February 2011.
Although smaller in magnitude, the earthquake was centred close to the CBD, causing extensive damage. Sadly this event caused the loss of 185 lives, making it New Zealand’s second deadliest natural disaster.
It was also easily New Zealand’s most expensive natural disaster. In fact, with an estimated total cost to insurers in excess of $13 billion from this shake alone, it’s one of the most expensive insured events in the world.
In addition to these major events, there have been more than 12,000 aftershocks, including more than 50 in excess of magnitude 5 – the most recent of these in May 2012. A further 520 were of a magnitude greater than 4 on the Richter Scale.