I’ve already covered the earthquake in Christchurch, New Zealand from a human perspective, including sharing a number of photos from the disaster, and covered the tremendous 30 million tons of ice the earthquake knocked off Tasman Glacier, the country’s largest glacier. Now, here’s a little more detail on the earthquake from the U.S. Geological Survey (USGS) and other earthquake experts.
This 2011 earthquake was reportedly quite shallow and very close to Christchurch. The temblor hit 3 miles (5 kilometers) from the city, according to the USGS, at a depth of 2.5 miles (4 kilometers). It was still a part of the “aftershock sequence” of the 7.1 magnitude earthquake that struck New Zealand on September 4, 2010, the USGS reports.
This quake hit “significantly closer to the main population center of Christchurch” than the September, 2010 earthquake (not sure why we don’t have names for major earthquakes like we do for hurricanes…). The shallowness made the impact and destruction especially severe.
“The critical issue with this earthquake was that the epicenter was at shallow depth under Christchurch, so many people were within 10 to 20 kilometers (6 to 12 miles) of the fault rupture,” said Gary Gibson, a seismologist at Australia’s Melbourne University. The September quake, in contrast, hit about 40 kilometers (25 miles) from the city.
According to Kevin Fenaughty, data center manager for GNS Science, this 2011 quake struck in the “worst possible location.”
“It felt like I was running on jelly,” one witness, Gavin Blowman, told CNN. “We saw a giant rock tumble to the ground from a cliff — a rock that had been there for millennia. It fell on the RSA (Returned Services Association, a veterans’ association) building — it was terrifying.”
In addition to the initial 6.3 magnitude earthquake, over 30 aftershocks, including aftershocks of magnitudes 5.6, 5.5, and 4.5, also hit the area within a few hours.
New Zealand sits on the well-known Pacific “ring of fire” — “an arc of earthquake and volcanic zones stretching from Chile in South America through Alaska and down through the South Pacific” — which produces approximately 14,000 earthquakes a year. 150 or so of those are felt by humans and less than 10 normally cause any damage to human infrastructure.
USGS information on the February 22, 2011 6.3 magnitude earthquake, 5.6 magnitude earthquake, 5.5 magnitude earthquake, 4.5 magnitude earthquake, and second 4.5 magnitude earthquake on the South Island of New Zealand.
Related Story: Narrowness of Ring of Fire Explained
Image Credit: USGS