SANTO (REUTERS/AFP) - A large magnitude-6.9 quake struck off the coast of the South Pacific islands of Vanuatu on Sunday, but a tsunami threat passed with no immediate reports of major damage along the coasts of the Pacific archipelago.
The Pacific Tsunami Warning Centre initially cautioned that "hazardous tsunami waves" were possible along the coasts of Vanuatu, but later updated its advice to say the threat had "mostly passed".
Mr Kanoa Koyanagi, a geophysicist at the Pacific Tsunami Warning Center in Hawaii said experts expected waves of no larger than 30cm, well below tsunami levels.
"Based on all data available... the tsunami threat from this earthquake has now mostly passed," the centre said in a statement.
The quake, initially reported as 7.2-magnitude, struck 151km north-north-west of Santo on Vanuatu, and 407km from the capital Port Vila, and was 35km deep, the United States Geological Survey (USGS) said.
The shallower a quake, the more damage it is likely to cause.
The USGS first measured the quake at 10km deep. There were no immediate reports of damage.
"There is a low likelihood of casualties and damage," the USGS added.
Australian government agency Geoscience Australia senior seismologist Jonathan Bathgate said that while residents of the town of Port Olry on Espiritu Santo island were likely to have felt "very intense shaking", "the likelihood is relatively low in terms of serious damage".
"I haven't had confirmation of anything (tsunami) impacting the northern coast of that (Espiritu Santo) island at this stage, so that's probably a good sign," Mr Bathgate told AFP.
He added that Port Vila residents would have "felt a shake but it probably wouldn't be damaging at that distance".
"Earthquakes such as this occur quite often in the area, so Vanuatu experiences these earthquakes of similar magnitudes probably fairly regularly," Mr Bathgate told AFP.
The Vanuatu Meteorological Services, a government department, said there were no reports of damage.
Dr Anna Romero, a doctor staying at a hotel near the town of Luganville on Santo told Reuters she felt the tremor, but saw no signs of damage.
Vanuatu is part of the "Ring of Fire", a zone of tectonic activity around the Pacific that is subject to frequent earthquakes and volcanic eruptions.