At 12.51 local time on February 22nd, a powerful earthquake of magnitude 6.3 occurred only 10km from Christchurch in New Zealand.
What has made this earthquake particularly devastating is that it occurred only 5 km below the surface which is a shallow depth.
Although not as powerful as the 7.1 earthquake that hit on September 4 last year, because of its location and depth this event has been far more catastrophic for Christchurch. The September quake was some 40 km from the city at a depth of about 10km below the ground.
The quake was one of the most devastating in the history of New Zealand, producing massive property damage and a death toll that may reach close to 200.
The Pacific "Ring of "Fire". Image from Wikipedia Commons - Click to enlarge)
New Zealand lies on the western branch of the so called Pacific Ring of Fire – a geologically active area that extends from New Zealand up through Tonga, New Guinea, Indonesia, the Phillipines, Japan, and down the west coasts of North and South America.
Earthquakes and volcanic activity are common along this ring but two major earthquakes near Christchurch only five months apart has not been seen before in recorded history.
The tectonic plates of the world -the Pacific Ring of Fire (in purple) follows a large part of the circumference of the Pacific plate. Image from Wikipedia Commons - Click to enlarge)
New Zealand lies across an area where the Australian tectonic plate grinds into the Pacific plate, creating an area of seismic instability.
The collision of these two plates also causes earthquakes around Tonga, Vanuatu and New Guinea.