The centre had warned that a tsunami might be destructive along the coasts near the epicentre of the two temblors, between Vanuatu and the Solomon Islands, but it later cancelled the warning after a 4cm tsunami was recorded at Lunganville on Espiritu Santo island in Vanuatu.
The US Geological Survey said the first quake, with a magnitude of 7.8, struck 294km northwest of the Vanuatu island of Santo, and 596km northwest of the capital of Port Vila, at a depth of 35km.
A second temblor, with a 7.3 magnitude, struck just 15 minutes at the same depth but 35km farther north of Santo and Port Vila.
A third quake of magnitude 5.7 was recorded nearly an hour later.
There were no immediate reports of injury or damage from officials in Vanuatu, a collection of nearly 200 islands.
"We have no damage reports yet, but we have had no contact with Santo so far," Take Rakau, a spokesman for the Vanuatu police, told the Associated Press news agency.
String of quakes
Coming just over a week after an 8.3 magnitude quake rocked the South Pacific near the Samoan islands, sparking tsunamis that killed around 180 people and devastated coastal villages in Samoa, American Samoa and Tonga, the authorities and residents took the alert seriously.
|Mothers in Fiji took their children to higher ground after the warning [Matai Akauola]
In Fiji, Matai Akauola, a journalist, told Al Jazeera that many workers had evacuated their offices and were moving to higher ground.
The authorities in New Caledonia, a French territory, closed schools and urged people to get to higher ground.
New Zealand's emergency management ministry told people not to be on beaches or boats near the coast.
Moments before the Pacific quakes, a magnitude 6.7 tremor struck southeast of the Sulu archipelago of the Philippines, which is still picking up the pieces from a typhoon that killed at least 22 people last week.
Last week's quake and tsunamis near the Samoan islands were followed by a separate quake near the Indonesian city of Padang in west Sumatra which flattened thousands of buildings in the city and left hundreds dead.
Thousands remain missing and relief workers are battling to get aid to thousands made homeless.
Off Samoa's southern coast, specialist search divers continued to look for bodies this week as funerals continue to be held almost daily in tsunami ravaged villages across the coast.