SYDNEY - Undersea earthquakes caused panic in the South Pacific on Thursday, sending islanders fleeing to higher ground on fears of a second devastating tsunami in as many weeks, but a series of waves proved to be tiny and harmless.

The Pacific Tsunami Warning Center issued a tsunami warning for the entire southwest Pacific, which included island resorts and Australia, New Zealand and Indonesia, after the quakes struck beneath the seas between Vanuatu and the Solomon Islands.

Hawaii and the Philippines were placed on tsunami watch. The center canceled its warning after three tsunamis, measuring up to 10 cm, were recorded in Vanuatu.

But with memories fresh of a tsunami last week that killed some 150 people in American Samoa and Samoa, many islanders panicked when the quake hit and tsunami warnings were issued.

People were frightened and some ran out of the building onto the street because it was so strong, Florence Cari, receptionist at Hotel Santo in Vanuatu, told Reuters by telephone.

A reporter at Vanuatu's Daily Post newspaper said people on Espiritu Santo island ran for higher ground. We have had reports that the kids are running into the hills, she said.

Some villagers in outlying islands in the Solomons reported tidal changes. People on the coastal areas have noticed a tide difference. The hospital is on alert, a hospital spokesman on tiny Nendo island in southwest Solomon Islands said by telephone.

The tsunami warning center issued its warning after two subsea quakes, one measuring 7.8 magnitude and the other 7.3. Late in the evening, the center reported another 7 magnitude quake but ruled out a tsunami threat. No details were immediately available.

Moments before the morning quakes, a magnitude 6.7 tremor struck southeast of the Sulu archipelago of the Philippines, which is still mopping up from a typhoon that killed at least 22 people.

Indonesia's port city Padang was hit by a 7.6 magnitude quake last week, killing 704 people and leaving 295 missing, but the health minister said the toll could reach 3,000.

SERIES OF QUAKES, ALARMING

Mike Sandiford, at the School of Earth Sciences, University of Melbourne, said the series of large quakes in the region was unusual and that aftershocks could be expected for a few weeks.

We only get about a dozen earthquakes of that magnitude or larger around the globe in a year, so it is very unusual, Sandiford told Australian media.

There will be a lot of questions to ask as to whether there is any relationship between these earthquakes.

Sandiford said the Australian Plate, which caused the Sumatran and Vanuatu quakes, was the world's fastest moving tectonic plate and was creating great stresses.

The Australian Plate is moving north/northeast, shoving over the Pacific Plate at 91 mm a year. The Sumatran quake was caused by a fault near the interface of the Australian Plate and Southeast Asia's Sunda Plate.
All these earthquakes are related to the fact that we live on a very dynamic and fast moving plate, said Sandiford.

Until now we would have thought quakes in Samoa and Sumatra and Vanuatu are too far apart to be caused in any other way than by mere coincidence. But it is certainly alarming that we have so many in such a short period of time.

(Additional reporting by Cecile Lefort in Sydney and Adrian Bathgate in Wellington; writing by Mark Bendeich; Editing by Ron Popeski)

Australia Earth Earthquake