An earthquake with a magnitude of 7.2 struck about 535km (330 miles) southeast of the South Pacific island nation of Vanuatu on Friday, the US Geological Survey said, briefly triggering a local tsunami warning.
There were no immediate reports of casualties or damage.
The Pacific Tsunami Warning Center issued a warning for areas close to the quake, although there was no Pacific-wide threat of a tsunami, the Hawaii-based centre said.
The tsunami warning, which had included coastal areas of Vanuatu, New Caledonia and Fiji, including the Fijian capital, Suva, was later cancelled.
The shallow quake was measured at a depth of about 10km (6 miles). It initially registered with a magnitude of 7.6 but was later downgraded.
The powerful quake triggered at least five aftershocks, ranging in magnitude from 4.7 to 5.4, the USGS said.