The underwater quake struck at 0627 GMT at a depth of 10 kilometers in the lightly populated area, the USGS said. The epicenter was also 877 kilometers east of Ushuaia, Argentina, the USGS said.
There were no initial reports of damage or casualties.
The Hawaii-based Pacific Tsunami Warning Center issued a bulletin stating that, despite the power of the quake, "a destructive widespread tsunami threat does not exist."
The USGS initially said that it was a magnitude 6.6 earthquake, but later revised the quake's strength.
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