A 7.2-magnitude earthquake struck the sea near Vanuatu on Saturday, October 24.
The USGS says the quake hit at 2:31 am UTC, 10 kilometres below the seabed.
The epicentre was about 200 kilometres west of the town of Sola.
The Pacific Tsunami Warning Centre warns of dangerous waves within 300 kilometres.
The centre names Vanuatu as the threatened coastline and tells agencies to alert people.
The first wave could reach Espiritu Santo around 3:01 am UTC, but times may differ.
The USGS also logged a separate 6.3 quake nearby and later revised the main quake to 6.9.
No deaths or damage have been reported so far, according to The Indian Express.
The warning centre says there is no tsunami threat to Hawaii or US Pacific territories.
The Philippines agency PHIVOLCS also says there is no tsunami threat to the country.
People on Vanuatu's coasts should stay alert and follow instructions from local authorities.
What the 7.2 quake means, why the size changed, and what happens next.
Get the full breakdown, key numbers, and what happens next.
Read on Rive News