Tuesday 31 January 2012

Large Earthquake near Ica, Peru.

Slightly after ten past midnight local time (slightly after 5.10 am GMT) on Monday 30 January 2012, an Earthquake measuring 6.3 on the Richter Scale occurred 15 km to the southeast of the Peruvian city of Ica at a depth of 39.2 km, according to the United States Geological Survey. This is quite deep, but 6.3 is a big Earthquake, and the effects were felt quite severely in the city and surrounding area.

Map showing the location of the quake, and the areas where it was most intensely felt. From the United States Geological Survey.

There are no reports of any fatalities, but the Earthquake-Report website is reporting 145 people injured, 12 of them seriously. In addition they are reporting 581 people have been made homeless and 762 living in damaged buildings, with two houses completely destroyed, 125 uninhabitable, and a further 150 damaged but still in use. There are also some reports of looting.

Raw video from the scene of the quake. Associated Press.

Peru is on the West Coast of South America, on the margin between the South American and Nazca Plates. The Nazca Plate, which underlies part of the Southeast Pacific, is being subducted beneath the South American Plate. This is not a smooth process, and the plates often stick together, adhering for a while as pressure builds up (the Nazca Plate is being pushed eastwards by an expansive centre under the Pacific, the South American Plate is being pushed westwards by an expansive centre under the Atlantic), then shifting abruptly, causing Earthquakes. As the Nazca Plate is drawn into the Earth's interior, it partially melts, and some of the melted material rises up through the overlying South American Plate, causing volcanoes in the Andes, but also leading to the mineral richness of much of the area.

Diagram showing the subduction of the Nazca Plate beneath the South American Plate, and the effects thereof. The green star represents an Earthquake. From the Pacific Earthquake Engineering Research Center.