The United States Geological Survey recorded a Magnitude 5.3 Earthquake at a depth of 10 km in southern Chihuahua State, Mexico, slightly after 6.15 am local time (slightly after 12.15 pm GMT) on Saturday 21 September 2013. This was followed approximately 25 minutes later by a Magnitude 4.8 aftershock at roughly the same depth. The initial quake was felt over a wide area, and caused damage to buildings and minor landslips up to 100 km away, although this was in part due to waterlogged soils in the aftermath of Tropical Storm Manuel and Hurricane Ingrid. There are, however, no reports of any casualties.
The approximate location of the 21 September 2013 Chihuahua Earthquakes. Google Maps.
Mexico has two major tectonic boundaries. To the east Baja California lies on the Pacific Plate is moving northwest with regard to the North American Plate, while the North American Plate is moving southeast relative to the Pacific Plate. This creates a transform plate margin along the center of the Gulf of California, as the two plates slide past one-another, a margin that continues northward under California as the San Andreas Fault. To the south, along the Middle American Trench, which lies off the southern coast off Mexico, the Cocos Plate is being subducted under the North American Plate, passing under southern Mexico as it sinks into the Earth.
While neither of these plate margins is close to Chihuahua, they do together contribute to a build up of tectonic pressure in the wider area, which occasionally causes Earthquakes as the rocks beneath the surface adjust their position to release this stress.
See also 58 feared dead following Mexican landslide, Landslide kills twelve bus passengers as Hurricane Ingrid makes landfall in Veracruz State, Mexico, Magnitude 4.1 Earthquake in northeast Baja California, At least eighteen deaths as Tropical Storm Manuel hits Guerro State in southern Mexico and Magnitude 4.2 Earthquake in Chihuahua State, Mexico.
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