Why Chile Had Such a Massive Earthquake

Chile's western boarder, some 2,653 miles in length, sets along side the Peru-Chile Trench. The Peru-Chile Trench is one of many subduction zones in the world such as seen along the California coast. Chile and the whole of South America ride upon the South American tectonic plate. To the west is the Nazca Plate. The South American Plate is being squeezed from the east and the west by two of the most active areas of seafloor spreading. To South America's east is the African Plate. The Mid-Atlantic Ridge, the area where the African and South American Plates meet, is spreading at a rate of 3.5 cm per year. To the west of South America is the East Pacific Rise, the area where the Pacific and Nazca Plates meet. Midway along the East Pacific Rise is the most active spreading in the world. Where the average rate of spreading around the world is about 3 cm per year, in comparison, the midpoint of the East Pacific Rise is racing at 15.6 cm (6.1 inches) per year according to data released in 1898. A movement of six inches seems insignificant, but you are looking at a tectonic plate that is larger than the entire United States. Something that size does not move without consequences.

Chile has had a long history of earthquakes dating back to the 1500's in recorded history. As the years and centuries have past, major earthquakes have been occurring at an ever more frequent rate to where they are now almost an annual event. Chile's most recent earthquake, measuring 8.8 on the Richter Scale, was tremendous, but it was not the largest in Chilean history. Fifty years ago on May 22, 1960 Chile experience a 9.5 magnitude quake. Over the next ten years or so the earthquakes will run in the 6^th magnitude as pressures build up for the next big quake that will take place between 2020 and 2025.