The Magnitude 8.2 quake that struck off the coast of Chile on April 1, 2014, was the latest in a series of major earthquakes and tsunamis to hit that area in recent years. The undersea quake and resulting 7 ft. (2.1m) tsunami killed 7, toppled buildings, and severely damaged the Chilean fishing fleet. Earthquake/tsunami events in 2010 (M8.8), 2007 (M7.7), 2005 (M7.8), and 2001 (M8.4) killed more than 1,000 and inflicted billions of dollars in property damage .
The most powerful earthquake ever recorded, a Magnitude 9.5, hit the coast of Chile on May 22, 1960. The monster quake triggered an 82 ft (25m) tsunami that not only battered the west coast of South America, but rolled across the Pacific Basin, devastating Hilo, Hawaii, and damaging coastal villages as far away as Japan and the Philippines. Some sources estimate 6,000 dead and $800 million in property loss (6 billion in 2014 dollars).
Why does this area of planet earth spawn so many high-magnitude earthquakes and punishing tsunamis?
One explanation is that the collision of the two tectonic plates that meet off the South American west coast occurs, in geologic terms, at a very high rate of speed. The oceanic Nazca Plate and the continental South American Plate converge in the Peru-Chile trench that lies about 100 mi (160km) off the coast. The overriding South American Plate moves eastward at 10cm a year, while the subducting Nazca Plate pushes west at 16cm/y, a closing velocity of 26cm/y (about 10 in.), one of the fastest absolute motions of any tectonic plate. The Africa Plate, for example, moves approximately 7 times slower.
This high closing velocity builds up fault line strain much faster than it does when slower-moving plates converge. Every few years, tension on the Peru-Chile fault line builds up to a breaking point. In this latest earthquake on April 1, a 100 mi. (160km) section of the fault line ruptured, allowing the Nazca Plate to ram under the South American Plate. This sudden violent action 12.5 mi (20.1km) below the ocean floor triggered the tsunami and the 8.2 earthquake, and at the same time wedged the South American Plate higher. Uplifting from frequent fault line failures continues to build the Andes Mountain Range into one of the highest in the world. During the 1960 M9.5 quake, some coastal areas uplifted as much as 10 ft. (3m).
As long as the two tectonic plates that meet off the South American coast move geologically at such high speed, major earthquakes and tsunamis will keep happening. We hope the zoning laws and building codes put in place by the governments of Chile and Peru will keep the damage and loss of life to a minimum.