Argentina hit by magnitude 6.3 earthquake

An earthquake measuring 6.3 on the Richter scale struck Argentina Monday, the United States Geological Survey reported.

The epicentre – in the Nazca plate region – was 93 kilometres northwest of San Luis, Argentina and 344 kilometres east-northeast of the Chilean capital, Santiago.

“Relative to a fixed South America plate, the Nazca plate moves slightly north of eastwards at a rate varying from approximately 80 mm/yr in the south to approximately 65 mm/yr in the north,” USGS says on its website.

Reuters quoted a journalist in San Luis as saying there were no immediate signs of damage.

There is a plate boundary “between the subducting Nazca plate and the South America plate, where the oceanic crust and lithosphere of the Nazca plate begin their descent into the mantle beneath South America,” USGS notes.

“Interplate earthquakes occur due to slip along the dipping interface between the Nazca and the South American plates.”

Several severe earthquakes have occurred in that subduction zone, including the largest earthquake ever recorded, on May 22, 1960. That was when a 9.5-earthquake caused a tsunami with wave heights exceeding 11 metres.

USGS reported that Monday’s tremor, which occurred at 5:49 am Eastern time, was at a depth of 172.3 km

“Large intermediate-depth earthquakes (those occurring between depths of approximately 70 and 300 km) are relatively limited in size and spatial extent in South America, and occur within the Nazca plate as a result of internal deformation within the subducting plate,” reports USGS. “These earthquakes generally cluster beneath northern Chile and southwestern Bolivia, and to a lesser extent beneath northern Peru and southern Ecuador, with depths between 110 and 130 km.”