A 7.3 magnitude earthquake is described as "very strong" by seismologists.
The quake struck the South Georgia island region at a depth of about 10 kilometres, according to the USGS.
The islands host a British Antarctic research station – around 1,500 miles east of the Falklands.
It was the centre of British whaling for decades until the trade was abandoned in the 1960s.
There were reports of tremors in the nearby Falkland Islands.
No immediate tsunami warning was issued.
It comes just months after a 7.2 magnitude quake struck the South Sandwich Islands.