Earthquake Summary
Earthquake Summary Poster
Tectonic Summary
The February 21, 2011 South Island, New Zealand earthquake occurred as part of the aftershock sequence of the M 7.0 September 3, 2010 Darfield, NZ earthquake. The February 21st earthquake involved oblique-thrust faulting at the easternmost limit of previous aftershocks, and like the mainshock itself is broadly associated with regional plate boundary deformation as the Pacific and Australia plates interact in the central South Island, New Zealand.
This latest shock is significantly closer to the main population center of Christchurch, NZ, than is the September 2010 mainshock, in the vicinity of several other moderate (M 4 to 5) sized aftershocks located east of the main rupture zone of the 2010 event. There is no specific structure directly linking this event to the main fault of the 2010 mainshock, although there have been numerous aftershocks along generally east-west linear trends extending east from the end of the previous rupture. The north or north-east trends to the possible fault planes and the oblique thrust faulting mechanism as seen in the focal mechanism solution may reflect an association with similarly-trending faults previously mapped in the Port Hills region, just to the south of Christchurch.
Since the September 3, 2010 mainshock, there have been approximately 6 M>=5.0 aftershocks in the Christchurch region. The February 21st earthquake represents the largest aftershock to date, more that half a magnitude unit larger than the previous largest aftershock.
Earthquake Information for New Zealand
The Piko Wholefood building in Christchurch was badly damaged by the earthquake. 
A magnitude 6.3 earthquake struck the  of New Zealand at 12:51 PM local time on Tuesday (Monday 23:51 UTC). At least 75 people have been killed by collapsing buildings in central , with more feared. Mayor  said 55 bodies had been identified and there were a further 20 unidentified bodies. The spire of the iconic Anglican  has fallen and rubble is strewn throughout the central business district. Roads and carparks have cracked and lifted, and two buses are reported to be crushed under the bus exchange. Pools of mud have erupted due to burst water mains and liquefaction.  Boulders and falling cliff faces have destroyed buildings on hillside suburbs.  Fears for the safety of nearby towns Lyttelton and Akaroa are exacerbated due to communication problems.

The earthquake was centred near , at a depth of five kilometres, according to the . Unlike previous quakes in the region that caused no fatalities, Tuesday quake was shallower and closer to the central city and the damage was much worse. Condemned buildings, weakened by last year's widespread earthquakes, were destroyed. Some aftershocks have occurred in the area after the earthquake. The largest so far was a magnitude 5.6 which occurred at 7:04 p.m. February 21  (1:04:18 p.m. local time, February 22). 

Mayor Bob Parker has stated that as many as 25 major buildings in the city are destroyed. Urban Search and Rescue efforts are focussed on people trapped in the remains of Canterbury Television and Pyne Gould Corporation office buildings. The historic  in Christchurch has half collapsed, while the old Canterbury Provincial Chambers building, Piko Wholefoods, and a church on Durham Street have been destroyed.

The earthquake also caused an estimated 30 million tons of ice to break off of the Tasman Glacier forming icebergs in a lake near its foot. Tourists on boats at the time of the quake say waves of 3.5 meters swept the lake for at least 30 minutes following the event. The glacier sits on the country's west coast, approximately 120 miles (200km) from Christchurch. No injuries were reported.

Many people are trapped in damaged buildings or under rubble, but emergency services have been hampered by gridlock as motorists and pedestrians evacuated the CBD. The main hospital remains operational despite one damaged ward being closed, and three triage centres have been set up to provide medical aid. Several hundred delegates attending a medical conference in the city, the great majority from Australia, have been trapped in the city; some of these are assisting with tending to the injured.

Electricity, telephone services, and traffic lights suffered widespread outages. Orion and Telecom are attempting to assess the damage, and generators have been sent down from Auckland to replace the backup generators in the city. Civil Defence is mounting a response with all available national resources, and Cabinet is holding an emergency session. Speaking to ,   said he was "thrown quite a distance", that there were scenes of "great confusion" on the streets, and that the quake was "as violent as the one that happened on the 4th of September". The emergency telephone code, 111 was not working for the entire region of  but is apparently stable as of approx. 4 pm . Christchurch Airport is currently closed to all but emergency flights. Speaking after the earthquake, Bob Parker said at least 200 people are believed trapped under rubble, saying that New Zealand are "going to be presented with statistics that are going to be bleak".