The quake's epicenter was 100 mileswest of Invercargill, off the west coast of New Zealand's South Island at a depth of 21 miles. It hit at 0922 GMT on Wednesday, the USGS said.
The Pacific Tsunami Warning Center in Hawaii sent an e-mail alert warning of a possible tsunami in New Zealand, but the warning was called off after waves no larger than eight inches washed ashore on a remote section of South Island's coast.
The quake was felt widely across South Island, where the earthquake was centered.
The Warning Center said there were no indications of a "destructive
tsunami threat to Hawaii."
Police in the town of Tuatapere on South Island said they had reports of minor cracks in buildings and stock falling from supermarket shelves.
However, no reports of serious damage or injuries were received, police said.