The seismic activity occurred at 2.32pm on May 13 at a shallow 10km depth, The Fiji Times reported.
The Mineral Resources department in Suva said the earthquake was registered at 183km south of Rabaul, or 654km north-east of Port Moresby.
The department said there was no immediate threat associated with the seismic activity, adding that it would continue to monitor and provide further updates.