An earthquake with magnitude 6.7 hit the Pacific Ocean off Vanuatu on Tuesday, said the US Geological Survey.
It was registered 75km (45 miles) from the country's largest island at 0918 (2218GMT Monday), centred deep below the earth's crust.
Experts said there was no risk of the tremor creating a tsunami.
But there is reportedly some risk of coastal towns, some of them only 80km (50 miles) from the epicentre of the quake, being affected.
Luganville, the country's second-largest town, on the island of Espiritu Santo is within that range.
There has been no impact in the capital, Port Vila, according to the director of Vanuatu's National Disaster Management Office.
But Job Esau told the Associated Press he was still waiting for news from outlying islands.
"We do expect some form of impact, whether it be a landslide or infrastructure damage so we're just waiting to hear," he said.
"Although it was a sizable earthquake ... the epicentre was 150 kilometres (93 miles) deep, which is too deep to deform the sea floor," said Gerard Fryer, a geophysicist at the Pacific Tsunami Warning Center in Hawaii.
"We've actually checked the tidal gauge at Port Vila and there's no risk of a tsunami at all."