A Magnitude 4.5 Earthquake at a depth of 197.2 km beneath the Altiplano (or Andean) Plateau in Jujuy Province in the northwest of Argentina, at 8.15 pm local time (11.15 pm GMT) on Wednesday 7 August 2013, according to the United States Geological Survey. A quake this small and this deep presents no real danger to people or structures at the surface, though apparently this one was felt by a number of people.
The approximate location of the 7 August 2013 Jujuy Earthquake. Google Maps.
Jujuy Province is located in the Andes Mountains, one of the most tectonically active mountain ranges in the world, and has a history of earthquakes. The Andes are being formed as the Nazca Plate to the west is subducted beneath the South American Plate. This causes quakes in a number of ways. Firstly there is friction between the two plates as the Nazca Plate passes under South America. Then there is crumpling and upthrust of the South American as it is pushed from the west by the Nazca Plate and from the east by the expansion of the Atlantic. Finally there is volcanic activity in the Andes, as lighter minerals in the Nazca Plate are melted by the heat of the Earth's interior, then rise up through the overlying South American Plate to form volcanoes.
See also Evacuations ordered after activity on Copahue, Eruption on Mount Copahue, Earthquake off the coast of Chiloé Island, Chile, Earthquake in eastern Chile and Earthquake in Jujuy Province, NW Argentina. 6 September 2011.
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