The earthquake occurred in the Banda Sea about 120 miles south of Ambon city, the USGS said. It occurred at a depth of 212 miles.
The Pacific Tsunami Warning Center said no destructive tsunami threat existed.
There were no immediate reports of damage or injuries.
Indonesia, the world's largest archipelago, is prone to seismic upheaval because of its location atop a volcanically active region known as the Pacific "Ring of Fire."
A Dec. 26, 2004, earthquake of magnitude 9 off the Indonesian coast generated a tsunami that left at least 216,000 people dead or missing and nearly 2 million homeless in 11 countries.
The true toll will probably never be known, many bodies were lost at sea and in some cases the populations of some places struck were not accurately known.