A Magnitude 8.8 Earthquake Strikes Chile

In the early morning hours of 27 February 2010, an 8.8 magnitude megathrust earthquake struck off the coast of central Chile. The tremor originated where the oceanic Nazca plate subducts beneath the continental South American plate, a tectonic boundary that converges at a rate of roughly 80 millimetres each year. The event ruptured a fault segment roughly 500 to 600 kilometres long and generated intense ground shaking lasting approximately three minutes. The shock wave affected six administrative regions encompassing roughly 80 percent of the national population, making it the most powerful earthquake in Chile since the 1960 Valdivia disaster.

The physical displacement along the fault produced dramatic geographical alterations across South America. Geodetic measurements revealed that the continental plate shifted abruptly westward during the rupture, moving the coastal city of Concepcion at least three metres to the west and displacing the capital city of Santiago by about twenty-eight centimetres. Even Buenos Aires, situated more than a thousand kilometres away on the Atlantic side of the continent, shifted a few centimetres. Vertical movement along the coast lifted land by more than two metres in places such as Santa Maria Island, exposing new rocks and wide beaches.