Wednesday 2 April 2014

Magnitude 8.2 Earthquake off the coast of northern Chile.

The United States Geological Survey recorded a Magnitude 8.2 Earthquake at a depth of 20.1 km roughly 70 km off the coast of northern Chile and 95 km to the northeast of the city of Iquique, slightly after 6.45 pm local time (slightly after 11.45 pm GMT) on Tuesday 1 April 2014. This is an extremely large and dangerous event, which the USGS estimates has a 7% chance of causing over 1000 casualties; at the time of writing 6 people are known to have died as a result of this event, and countries around the southern Pacific remain on tsunami alert.

Chilean firefighters tackle a blaze caused by the 1 April 2014 Iquique Earthquake. Aldo Solimano/Getty Images.

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 friction and the heat of the Earth's interior. Some of the melted material then rises up through the overlying South American Plate as magma, fueling the volcanoes of the Chilean Andes.

The approximate location of the 1 April 2014 Iquique Earthquake. Google Maps.

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

Earthquakes along subductive margins are particularly prone to causing tsunamis, since these often occur when the overlying plate has stuck to the underlying plate, being pulled out of shape by its movement.. Eventually the pressure builds up tp far and the overlying plate snaps back, causing an Earthquake and a tsunami. There have been reports of waves of up to 2.5 m in height reaching the Chilean coast after the 1 April 2014 Earthquake, prompting evacuations along much of the coast of Chile and neighbouring nations.

Simplified graphic showing tsunami generation along a convergent margin. NASA/JPL/CalTech.

See also...

 Series of major Earthquakes shakes northeast Chile.

 Magnitude 4.2 Earthquake in northern Chile.

 Magnitude 5.5 Earthquake in northeast Chile.

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