The squeeze one plate puts on the other as it slides back into the Earth’s mantle is building the Andes. When an event such as today’s quake occurs, it’s like a growth spurt, pushing the overlying crust up by several feet. That sudden displacement of mass underwater triggered the tsunamis that spread into the Pacific basin.
Today’s rupture occurred along a 248-mile length of a zone that traces the outline of most of South America’s west coast. The amount of slip was on the order of 30 feet, says Ray Russo, a University of Florida geophysicist whose research focuses on the region. He estimated that the crust closest to the epicenter may have experience uplift of three feet or more.
A more firm number will emerge after he and colleagues see GPS and radar-satellite data, he says.
Large earthquakes along the Nazca subduction zone – indeed along all of the earth’s subduction zones – are common. Globally, quakes with magnitudes comparable to today’s temblor occur on average once a year.
Since the 1970s, some 15 quakes in the magnitude 7 and 8 range have occurred along the Nazca’s subduction zone. The global-record holder occurred in 1960, when a magnitude 9.5 quake struck off the coast south of Conception.