MANILA, Philippines?A sudden cluster of massive earthquakes, which has shaken Asia-Pacific communities and likely left thousands dead, has also jolted some scientists, who are starting to question conventional thought.

Experts, who had dismissed the notion that far-away quakes could be linked, are beginning to have second thoughts after huge tremors rocked Samoa and Indonesia on the same day, followed by another major convulsion in Vanuatu.

Thursday?s magnitude 7.6, 7.8 and 7.3 earthquakes in Vanuatu also came just minutes after a large tremor shook the Philippines.

Some 184 people died in the terrifying tsunami that smashed into Samoa, American Samoa and Tonga on Sept. 30, while thousands are feared dead after parts of Indonesia?s Padang city were reduced to rubble just hours later.

On Thursday, thousands of panicked people fled the coast as a rapid succession of large quakes off Vanuatu set off a tsunami warning for much of the South Pacific.

At 10:41 a.m. on Oct. 8, a very deep magnitude-6.7 earthquake was recorded in the Celebes Sea, 320 km south of Zamboanga in Mindanao.

The ?remarkable? sequence has prompted veteran earthquake-watcher Gary Gibson to tear up his theory that it all came down to chance and to search for a possible connection.

?I can no longer keep using the response that it?s all a big coincidence, can I?? Gibson, senior seismologist at Environmental Systems and Services consulting group in Australia, told Agence France Presse.

Link between Samoa, Indonesia

?But what would the (link) mechanism be? Nobody has come up with a good story.?

University of Queensland?s Huilin Xing also challenged accepted science by proposing a possible link between the Samoan and Indonesian earthquakes?9,660 km apart.

Xing said the fast-moving Australian tectonic plate may have set off one quake, and then the other.

?From the observations, there were similar correlations of the quakes in the different places,? Xing said. ?For two great earthquakes to occur within hours in such a way, it is abnormal.?

The Philippines, located in the Pacific Rim of Fire where earthquakes and volcanic eruptions occur regularly due to the movement of tectonic plates, is hit by daily quakes, most of them not felt by the people.

Valley Fault System

Scientists expect a big quake to hit Metro Manila, home to 12 million people, at any time. If the government fails to prepare, a magnitude-7 temblor from the Valley Fault System (formerly known as the Marikina Valley Fault System) would affect around 38 percent of residential buildings, 14 percent of high-rise buildings and 35 percent of public buildings in the metropolis, according to the Philippine Institute of Volcanology and Seismology.

A magnitude-7.8 quake struck northern Luzon on July 16, 1990, killing 1,621 people.

?It?s remarkable. I?ve been working on this for 30 years and I?ve never seen it (series of big quakes) before,? said Gibson.

?Many times it?s chance, but when you get these many large earthquakes on the Australian plate boundary, it?s stretching the concept of just coincidence. But nobody I know has published a link that will stand up in all cases.

Historical precursor

He said there was no mechanism that anybody had thought of to describe why it was happening. ?I personally think there may well be something else and I?m continuing to look for it,? he said.

Kevin McCue, president of the Australian Earthquake Engineering Society, rejected ideas of any connection between the Pacific and Indonesian quakes, but said the tremors in Samoa and Vanuatu had a historical precursor.