An earthquake registering 6.3 ML struck Christchurch, New Zealand, killing 185 people and causing around NZ$40 billion in damage.

A major earthquake occurred in Christchurch on Tuesday 22 February 2011 at 12:51 p.m. local time. The M_w6.2 earthquake struck the Canterbury Region in the South Island, centred 6.7 kilometres (4.2 mi) south-east of the central business district. It caused widespread damage across Christchurch, killing 185 people in New Zealand's fifth-deadliest disaster. Scientists classified it as an intraplate earthquake and a potential aftershock of the September 2010 Canterbury earthquake.

The Richter scale, also called the Richter magnitude scale, Richter's magnitude scale, and the Gutenberg–Richter scale, is a measure of the strength of earthquakes, developed by Charles Richter in collaboration with Beno Gutenberg, and presented in Richter's landmark 1935 paper, where he called it the "magnitude scale". This was later revised and renamed the local magnitude scale, denoted as ML or M_L .

Christchurch is the largest city in the South Island and the second-largest city by urban area population in New Zealand. Christchurch has an urban population of 412,000, and a metropolitan population of over half a million. It is located in the Canterbury Region, near the centre of the east coast of the South Island, east of the Canterbury Plains. It is located near the southern end of Pegasus Bay, and is bounded to the east by the Pacific Ocean and to the south by the ancient volcanic complex of the Banks Peninsula. The Avon River / Ōtākaro winds through the centre of the city, with a large urban park along its banks. With the exception of the Port Hills, it is a relatively flat city, on an average around 20 m (66 ft) above sea level. Christchurch has a reputation for being an English city, with its architectural identity and nickname the 'Garden City' due to similarities with garden cities in England, but also has a historic Māori heritage. Christchurch has a temperate oceanic climate with regular moderate rainfall.