No damage or casualties have been reported.
Chilean authorities issued an evacuation alert for the entire coastal section of the Strait of Magellan, in the far south of the country.
Due to a "tsunami alert, evacuation to a safe zone is being ordered for the coastal sectors of the Magallanes region," Chile's National Service for Disaster Prevention and Response said in a message sent to the public.
It also requested that all beach areas in the Chilean Antarctic territory be abandoned.
Chilean President Gabriel Boric wrote on X that "all resources are available" to respond to potential emergencies.
"We are calling for the evacuation of the coastline throughout the Magallanes region," Boric wrote.
"Right now, our duty is to be prepared and heed the authorities."
In the Argentine city of Ushuaia, considered the world's southernmost, local authorities suspended all types of water activities and navigation in the Beagle Channel for at least three hours.
No material damage was reported.
"The earthquake was felt primarily in the city of Ushuaia and, to a lesser extent, in towns across the province," the local government reported.
"In the face of these types of events, it is important to remain calm."
The USGS said the quake's epicentre was in the Drake Passage under the ocean 219km south of the Argentinian city of Ushuaia.
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