A 5.2 magnitude earthquake struck the Arizona/New Mexico border on June 29, 2014, approximately 50 km (31 mi) from Lordsburg, New Mexico. Shaking was felt as far west as Payson, Arizona. The quake caused little damage, and was followed by a series of small, low magnitude aftershocks. Though the earthquake was low magnitude, seismic activity of this scale is very rare in this region. The event is a result of shallow normal faulting along a steep fault plane, most commonly associated with an extensional tectonic regime. Extension is caused by diverging plate boundaries, in which two tectonic plates move in opposite or oblique directions. This forms mid-ocean ridges, mantle plumes, hot spots, and rift valleys such as the East African Rift near Ethiopia. Southeast Arizona and southern New Mexico are both located in the Basin and Range Province at the edge of the Colorado Plateau. This region is being ripped apart via continental rifting.
The image below depicts the Basin and Range Province rift cutting through the southwest United States. The yellow arrows indicate the direction of movement. The Colorado Plateau is an unusually stable, uplifted region at the edge of the rift zone. Image retrieved from Parks and Plates, Â© Robert Lillie.
The following video from the Incorporated Research Institutions for Seismology (IRIS) (in collaboration with EarthScope, USGS, and Volcano Video and Graphic) demonstrates the movement of a normal fault. For more information and videos on the four basic classes of faults, visit the IRIS website.
EarthScope's Plate Boundary Observatory (PBO) is a series of Global Positioning System (GPS) stations, borehole seismometers, borehole strainmeters, and borehole tiltmeters spanning the North American continent. The observatory collects data on tectonic plate movements and boundary activity, deformations processes and rates, rheology (flow of matter) of the lithosphere, and episodic tremor and slip (ETS) activity. This research may help scientists predict when, where, and how an earthquake will happen, and what effect it will have on the nearby human populace.