What were the causes of the Christchurch earthquake?

Answer 1

The September earthquake in Christchurch occurred as a result of movement between the Australian and Pacific Tectonic Plates. The movement of which affects the NZ Southern Alps. It is usual for these plates to move up to 4cms annually, however, the September quake was believed to have seen movement of up to 5meters.

The earthquake that occurred on the 22nd February was one of the many aftershocks as a result of the September quake, however, the reason that the February earthquake was so much more violent and caused fatalities, was because of the aftershock was incredibly shallow and closer to the CBD than the original September quake.

Answer 2

The Christchurch earthquake on February 22, 2011, was caused by the rupture of a previously unknown faultline known as the Port Hills Fault. The rupture released stress that had been building up in the Earth's crust, resulting in the devastating earthquake. The region's location on the boundary between the Pacific and Australian tectonic plates also contributed to the seismic activity.