The islands are uninhabited except for the permanently manned Raoul Island Station, the country's northernmost outpost.
The region has long been a source of volcanic activity.
The earthquake's epicenter, about 21 miles deep, was about 100 miles south of Raoul Island, about 683 miles south-southwest of Nuku'alofa, Tonga, and 2,009 miles west-southwest of Papeete, Tahiti, the USGS said.
The Kermadec Islands are about 500 to 620 miles northeast of New Zealand's North Island.
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