Fresh off the heels of a magnitude-8.2 earthquake off the coast of northern Chile Tuesday night, a powerful aftershock struck the country late Wednesday.
A magnitude-7.6 tremor was reported just miles southwest of Iquique, Chile. It caused buildings to shake in the port of Iquique, which saw some damage from the big quake on Tuesday. There were no reports of new damage or injuries. The Pacific and national tsunami warning centers said Wednesday there is no threat of a tsunami to U.S. coastal states.
The latest tremor came 45 minutes after a strong 6.4-magnitude aftershock shook the same area. At 7.6, the aftershock was stronger than any earthquake to hit the continental U.S. since the 1906 San Francisco earthquake, which registered at 7.8, according to the United States Geological Survey.
The USGS says aftershocks can continue over a period of weeks, months or even years. In general, the larger the main earthquake, the larger and more numerous the aftershocks, and the longer they will continue.
In the wake of Tuesday's earthquake, six people had been killed, either from being crushed by debris or suffering heart attacks in the event. The quake has also set off a tsunami that forced evacuations along the country's entire Pacific coast.
Among those moved inland during the aftershock was President Michelle Bachelet, who was in the city of Arica assessing damage in the north from Tuesday night's powerful quake.
"I was evacuated like all citizens. One can see that the people are prepared," she tweeted early Thursday.
Chile's evacuation order was lifted at around 2 a.m. Thursday. The whole coast also was evacuated for several hours after Tuesday's quake, and for the night in the north, although the tsunami proved small.
The aftershock caused buildings to shake and people to run out into the streets in the port of Iquique, which was one of the cities that suffered damage from the Tuesday earthquake. There were no immediate reports of serious damage or injuries from the aftershock, which was one of dozens that have followed the magnitude-8.2 quake.
State television said the aftershock caused some landslides near Alto Hospicio, a poor area in the hills above Iquique where about 2,500 homes were damaged by Tuesday' earthquake.
The Ministry of Education suspended classes again in schools in the north for Thursday.
(PHOTOS: Massive Earthquake Slams Chile)
The aftershock was felt across the border in southern Peru, where people in the cities of Tacna and Arequipa fled buildings in fear. Police Lt. Freddy Cuela in Tacna said no damage or injuries were reported. Peru's navy tweeted a tsunami alert for the country's extreme southern coast, which is next to the Chilean region hit by the quakes.
Earlier, authorities reported just six deaths from Tuesday's magnitude-8.2 quake, but didn't rule out the possibility others could have been killed in older structures made of adobe in remote communities that weren't immediately accessible.
The tsunami after Tuesday night's quake caused the sea to rise only 8 feet (2.5 meters) in Iquique, a city of nearly 200,000 people, although that was enough to sink and damage many fishing boats. Iquique's fishermen poked through the wreckage Wednesday trying to assess what it will coast to repair and replace.
Still, as Bachelet deployed hundreds of anti-riot police and soldiers to prevent looting and round up escaped prisoners, it was clear the loss of life and property could have been much worse from Tuesday's powerful tremor.
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Tuesday night's mandatory evacuation lasted 10 hours in Iquique and Arica, the cities closest to the epicenter, and kept 900,000 people out of their homes along Chile's coast. The order to leave was spread through cellphone text messages and Twitter, and reinforced by blaring sirens in neighborhoods where people regularly practice earthquake drills.
But the system has its shortcomings: The government has yet to install tsunami warning sirens in parts of Arica, leaving authorities to shout orders by megaphone. And less than 15 percent of Chileans have downloaded the smartphone application that can alert them to evacuation orders.
Chile is one of the world's most earthquake-prone countries, and tsunamis are a particular danger because of activity in the fault zone just offshore where the Nazca tectonic plate plunges beneath the South American plate.
Information from the Associated Press was used in this report
Part of a chair floats in a flooded area of Iquique, northern Chile, on April 2, 2014 after a powerful 8.2-magnitude earthquake hit off Chile's Pacific coast. (Aldo Solimano/AFP/Getty Images)