In general, magnitude 8 quakes are capable of causing tremendous damage. Quakes of magnitude 2.5 to 3 are the smallest generally felt by people, and every increase of one number on the magnitude scale means that the quake's magnitude is 10 times as great.

The temblor occurred in one of the most seismically active regions in the world at the boundary where the Nazca and South American tectonic plates meet. The plates are moving together at a rate of 3 inches a year, Earle said.

The last time a quake of magnitude 7.0 or larger struck Peru was in September 2005, when a 7.5-magnitude earthquake rocked the country's northern jungle, killing four people. In 2001, a 7.9-magnitude quake struck near the southern Andean city of Arequipa, killing 71.

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Associated Press writers Monte Hayes, Edison Lopez and Leslie Josephs in Lima, Edith M. Lederer at the United Nations, Alicia Chang in Los Angeles and Sarah DiLorenzo in New York contributed to this report.