Coastal Chile has been rocked by severe earthquakes numerous times in the past, with 13 events of magnitude 7.0 or greater since 1973, according to the National Earthquake Information Center in Golden.
The strongest quake ever recorded in the world — 9.5 in 1960 — occurred about 140 miles south of Saturday's 8.8-magnitude temblor. In 1922, an 8.5-magnitude quake struck about 540 miles to the north.
"This is one of the most seismically active regions in the world," said Dale Grant, a geophysicist with the national center. "This is very normal. It's the way the Earth releases stresses over time."
Saturday's quake occurred at the boundary between the Nazca and South American tectonic plates, which are converging at a rate of about 3 inches per year.
The Nazca plate is moving down and below the South American plate, Grant said.
The 8.8-magnitude temblor originated from about 22 miles below the surface and could be felt throughout South America.
More than 70 aftershocks, most in the 5.0-magnitude range but a few as strong as 7.0, were recorded by Saturday afternoon. Grant said "good-sized" shaking will continue for weeks.
"Basically, after an earthquake like this ruptures over such great distances, the Earth tries to reset itself," Grant said. "With a shallow quake, it keeps bouncing back and forth."
Strong earthquakes have been reported worldwide in the past few months. Haiti's quake measured 7.0 on Jan. 12; a 7.0 quake hit Japan's Ryukyu Islands on Friday; and a 4.4 quake struck central Oklahoma on Saturday.
But Grant said nothing unusual is going on.
"This is the way the Earth behaves, and it is behaving badly right now," he said.
Ann Schrader: 303-954-1967 or aschrader@denverpost.com
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Chile's strongest earthquakes
May 22, 1960: A magnitude- 9.5 earthquake in southern Chile and ensuing tsunami killed at least 1,716 people. It is the strongest quake ever recorded in the world.
Aug. 13, 1868: A magnitude- 9.0 quake in Arica, Peru (now Chile) generated catastrophic tsunamis; more than 25,000 people were killed in South America.
July 8, 1730: A magnitude-8.7 quake in Valparaiso, Chile, killed at least 3,000 people.
Sources: U.S. Geological Survey; Incorporated Research Institutions for Seismology; WHO's International Disaster Database
Source:denverpost.com/
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