An initial, medium depth, M7.1 earthquake shook Christchurch before dawn on 4 Sep 2010. Because of the strength, depth and timing, damage was extensive but casualties were light.
As Christchurch was rebuilding, a shallower (5 km) quake of M6.8 struck around lunchtime on 22 Feb 2011, damaging many buildings and causing hundreds of casualities. Fortuitously for the city, many units of the NZ Defence Forces were stationed locally in preparation for a military exercise.
HMNZS Canterbury was in nearby Lyttleton and a disaster relief operation was instigated. Within hours there were hundreds of troops assisting local Police units, principally from 3 Land Force Group in Burnham. Within days, nearly 1500 military personnel were on the ground supplemented by 2 Land Force Group from Linton. The teams assisting the Police and Fire services provided safety and security watches, meals for the homeless and heavy equipment and vehicles for the immediate clearance operations.