A powerful 7.8-magnitude aftershock hit Chile's far-northern coast on Wednwsday, shaking the same area where a magnitude-8.2 earthquake hit just a day before causing some damage and six deaths.
Chile's Emergency Office and Navy issues a tsunami alert and ordered a precautionary evacuation of low-lying areas on the northern coast, meaning many people could be spending another sleepless night away from their homes.
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 saw some damage from Tuesday night's big quake. But there were no immediate reports of new damage or injuries from the latest tremor, which was one of dozens that have followed the 8.2 quake.
The aftershock was center 23 kilometers south of Iquique. The USGS said the aftershock had a depth of 20 kilometers.
It was felt across the border in southern Peru, where people in the cities of Tacna and Arequipa reportedly fled buildings in fear.
Authorities reported just six deaths from the 8.2-magnitude quake. It was possible others could have been killed in older structures made of adobe in remote communities that weren't immediately accessible, but it was still a very low toll for such a powerful shift in the undersea fault that runs along the length of South America's Pacific coast.
Chile is one of the world's most seismic countries and is particularly prone to tsunamis, because of the way the Nazca tectonic plate plunges beneath the South American plate, pushing the towering Andes cordillera ever higher.