A major 7.5-magnitude earthquake hit off the coast of the South Pacific island of Vanuatu on Sunday, the US Geological Survey said, but there was no immediate tsunami warning issued.
The quake struck at 3:55 am (1655 GMT Saturday) at a depth of 40 kilometres (25 miles), around 60 kilometres south of Port Vila, the capital of the island nation.
There was no tsunami warning in effect on the Hawaii-based Pacific Tsunami Warning Center website and there were no immediate reports of damage.
Minutes after the first quake a second smaller 5.9-magnitude tremor was detected by seismologists.
Vanuatu lies on the so-called "Pacific Ring of Fire", a zone of frequent seismic activity caused by friction between shifting tectonic plates.