The U.S. Geological Survey reported the quake, which hit at at 6:46 p.m. local time, was centered some 60 miles northwest of Iquique at a depth of 12.5 miles. It had previously put the magnitude at 8.0 and the depth at 6.2 miles.
The quake caused a small landslide, but there we no reports of deaths or major damage, Chilean Deputy Interior Minister Mahmud Aleuy told reporters.
Chile's National Emergency Office tweeted Tuesday night that it was asking everyone to evacuate the South American nation's coast.
People in Antofagasta, a port city, walked through the streets as traffic piled up in some places, video on CNN Chile showed. They appeared to be calm.
A tsunami warning was in effect for Chile, Peru, Ecuador, Colombia and Panama. A tsunami watch was issued for Costa Rica, Nicaragua, El Salvador, Guatemala, Mexico and Honduras, according to the Pacific Tsunami Warning Center.
"Sea level readings indicate a tsunami was generated. It may have been destructive along coasts near the epicenter and could also be a threat to more distant coasts," the center said in its evaluation.
Tsunami waves of more than 6 feet generated by the earthquake had already washed ashore on the coast of Pisagua, Chile, according to Victor Sardino, with the center. The center said nearly 7-foot waves were reported in Iquique, Chile.
According to the Global Disaster Alert and Coordination System -- a joint effort that includes the United Nations -- the city of Iquique has a population of more than 200,000 people.
Although there were no immediate reports of injuries, an 8.2-magnitude earthquake is capable of causing tremendous damage.
Chile is on the so-called "Ring of Fire," an arc of volcanoes and fault lines circling the Pacific Basic that is prone to frequent earthquakes and volcanic eruptions.
On March 16, a 6.7-magnitude earthquake struck 37 miles west-northwest of Iquique, according to U.S. Geological Survey. A 6.1-magnitude hit the same area exactly one week later.
About 500 people were killed when a 8.8-magnitude earthquake struck Chile on February 27, 2010. That quake triggered a tsunami that toppled buildings, particularly in the Maule region along the coast.
According to researchers, the earthquake was violent enough to move the Chilean city of Concepcion at least 10 feet to the west and Santiago about 11 inches to the west-southwest.
The tsunami threat to Hawaii still was being evaluated Tuesday. The U.S. National Tsunami Warning Center was working to determine the level of danger for Alaska, Washington, Oregon and California, as well as Canada's British Columbia.
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