Earthquakes around the globe have caused concern, and even deaths, over the President’s Day weekend. The most significant earthquake occurred on South Island, New Zealand, which resulted in significant structural damage and mass injuries and fatalities.
According to the U.S. Geological Survey, the deadly earthquake in New Zealand started at 12:51 pm, New Zealand Time, on Tuesday, February 22 (23:51 Greenwich Mean Time on Monday, February 21). The magnitude 6.3 earthquake was had an epicenter near Christchurch, New Zealand, and was approximately 3 miles deep.
This earthquake, according to the USGS and GeoNet, is being considered an aftershock of 7.0 magnitude earthquake that hit the same region of New Zealand on September 4, 2010. The primary difference, according to a news release from the USGS, is that the 7.0 earthquake, while larger, was further away from the urban center of Christchurch than the 6.3 aftershock.
In comparing details from the two quakes, provided by GeoNet.org.nz, a collaboration between New Zealand’s Earthquake Commission and GNS Science, a geoscience consultancy group in New Zealand, both earthquakes clearly caused damage to Christchurch and the surrounding areas. The damage caused by February’s quake appears to be directly linked to the epicenter’s proximity to Christchurch as well as its relative shallow location.
For comparison purposes, the February 22 quake occurred less than 5 km(3.1 miles) from Christchurch at 12 km (7.5 miles) below the surface. The September 4 quake occurred was approximately 10 km(6.2 miles) deep and 40 km (24.9 miles) west of Christchurch.
TVNZ, a nationwide news and media outlet in New Zealand, has received reports from the Civil Defence of confirmed fatalities. This is in stark comparison to the September quake where there were no confirmed casualties. Initial reports continue to flood the network and government offices of building collapses, injuries, deaths, landslides and even boulders the size of two story houses rolling off mountaintops.
It is important to note that this incident is in the Response phase of the emergency management cycle. One of the characteristics of the response phase is the widespread use of communication technology to notify first responders and emergency responders. Due to the large number of calls into emergency services, like American 911 call centers, it is likely that much of the information reported in the immediate aftermath of a disaster is either incorrect and under/over reported. As the timeline runs in this phase of the response, expect to see initial reports to be confirmed (either true or false), retracted and modified extensively. More information about the emergency management cycle can be found here.
Also, according to the USGS, over the weekend, a swarm of earthquakes plagued the Arkansas area known as the New Madrid Seismic Zone. The swarm of earthquakes, the largest of which measured in at 4.1 in magnitude, occurred on February 18, 2011. There were no known reports of injuries or damage associated with those earthquakes.