Monday 18 September 2017

Magnitude 5.8 Earthquake off the coast of Choapa Province, Chile.

The United States Geological Survey recorded a Magnitude 5.8 Earthquake at a depth of 10 km, 95 km offshore of the city of Illapel in the Chilean province of Choapa, slightly after 10.45 am local time (slightly after 1.45 pm GMT) on Monday 18 September 2017. There are no reports of any damage or injuries associated with this event, but people have reported feeling the event in the Santiago and Valparaiso areas.

The approximate location of the 18 September 2017 Antofagasta Earthquake. USGS.

Chile is located on the west coast of South America, which is also the convergent margin between the Nazca and South American Plates. The Nazca Plate is being subducted beneath the South American Plate and is sinking beneath the South American Plate. This is not a smooth process, the rocks of the two plates continuously stick together then, as the pressure builds up, break apart again, causing Earthquakes. As the Nazca Plate sinks deeper it is partially melted by the heat of the Earth's interior. Some of the melted material then rises up through the overlying South American Plate as magma, fuelling the volcanoes of the Chilean Andes.
 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 organisation 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.
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