Sunday 18 October 2015

Deadly Earthquake in Salta Province, Argentina.

At least two people has died and a number of others have been treated for crush injuries following an Earthquake in Salta Province in northwest Argentina. The event was measured by the United States Geological Survey as occurring slightly after 8.30 am local time (slightly after 11.30 am GMT) on Saturday 17 October 2015, and having a Magnitude of 5.9 and a depth of 8 km. All of the casualties have been reported from the town of El Gálpon, about 21 km to the west of the epicenter of the quake (the point on the surface directly over the focus of the Earthquake), where at least fifteen homes and a school have collapsed.

Damage in the town of El Gálpon, Argentina, following the 17 October 2015 Earthquake. Rueters.

Salta Province is located on the eastern margin of the Andes Mountains, one of the most tectonically active mountain ranges in the world, and the plains to the east of these mountains. 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.

The approximate location of the 17 October 2015 El Gálpon Earthquake. Google Maps.

This means that Earthquakes, even large events, are quite common in the area, but since the province is on the eastern margin of the Andes, such quakes usually happen at considerable depth (the margin between the Nazca and South American plates is angled downwards, so that maximum seismic activity happens close to the surface on the coast of Chile and deep within the Earth beneath eastern Argentina), so that much of the energy from the quake is dissipated before it reaches the surface. However the 17 October 2015 event happened at a much shallower depth, with the effect that people living in El Gálpon felt almost the full force of the event.

The subduction of the Nazca Plate beneath the South American Plate, and how it causes Earthquakes and volcanoes. Pacific Earthquake Engineering Research Center.

Witness accounts of Earthquakes can help geologists to understand these events, and the structures that cause them. The international non-profit organization Earthquake Report is interested in hearing from people who may have felt this event; if you felt this quake then you can report it to Earthquake Report here.

See also...

The United States Geological Survey recorded a Magnitude 4.9 Earthquake at a depth of 8.5 km in southern La Rioja Province, Argentina, at about...

The United States Geological Survey recorded a Magnitude 5.5 Earthquake at a depth of 19.3 km in Mendoza Province, eastern Argentina, slightly before 3.20 am local time (slightly before 6.20 am GMT)...

The United Sates Geological Survey recorded a Magnitude 4.6 Earthquake at a depth of 32.4 km in eastern Catamarca Province, Argentina, roughly 45...

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