2004 Samoan tsunami caused by 'shallow quake', say scientists

Sydney, October 1 (ANI): Scientists have determined that the tsunami that devastated the islands of Samoa, American Samoa and Tonga in 2004 was the result of a shallow rupture in the earth's crust.

The earthquake, which was measured as high as 8.3 on the Richter scale, occurred 190 kilometres southwest of American Samoa.

According to a report by ABC News, Gary Gibson, a senior seismologist at Environmental Systems and Services in Melbourne, the region experiences several magnitude 7 earthquakes each year, but a magnitude 8 is quite rare.

"The earthquake had a magnitude of about 8, which corresponds to a rupture within the earth that may be 200 to 300 kilometres long, with a depth of 100 to 200 kilometres, with one side of the fault moving four to seven metres relative to the other," said Gibson.

He said that the energy released in the earthquake was approximately one-thirtieth the size of the Boxing Day 2004 earthquake near the island of Sumatra, Indonesia.

"This meant that a devastating tsunami could be produced locally, but it was unlikely to seriously affect countries on the boundary of the Pacific," he said.

Gibson said that residents of the nearby islands would have felt the earthquake last for at least a minute, which is a sure sign of an impending tsunami.

"Anyone who feels an earthquake last for more than 10 seconds, by definition, should expect a tsunami. It's nature giving you a warning," he says.

Gibson estimates that the tsunami would have taken 20 minutes to reach the islands of Samoa and American Samoa.

Reports from American Samoa say waves of up to three metres washed onto the island, causing widespread destruction.

Authorities have confirmed that the tidal surge killed 28 people across the islands, but they fear the final toll could be as high as 100.

After the earthquake, the Pacific Tsunami Warning Centre issued a tsunami warning for South Pacific nations, including New Zealand, which experienced a rise in sea level of 40 centimetres. (ANI)