The Hindu : National : Scientists come out with startling details of tsunami

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Thursday, Dec 22, 2005

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Scientists come out with startling details of tsunami

Special Correspondent

The wave travelled around the world thrice before expending its energy fully The entire fault line in the Indian Ocean runs for 1,600 miles and only half of it ruptured last year. Scientists believe that the other half could break any time.

MUMBAI: A 27-member team of scientists that explored the seabed site of last year's tsunami has come out with amazing and chilling details of the geological catastrophe that claimed thousands of lives.

The entire fault line in the Indian Ocean runs for 1,600 miles and only half of it ruptured last year.

The team led by noted oceanographer Kate Moran of the University of Rhode Island, U.S., believes that the other half could break any time.

The Discovery Channel that funded the 17-day expedition recently is to air a special programme — Unstoppable Wave — on Christmas day and also on December 26, the first anniversary of the catastrophe.

The scientists belonged to several disciplines, including seismology, geophysics and marine biology. They were backed by seabed visualisation experts and tsunami modellers. Among them was an Indian marine biologist, Baban Ingole of the National Institute of Oceanography, Goa.

Dr. Ingole described the expedition and the research method at a press conference here on Wednesday. The researchers lowered ROV — remote operated vehicle, suspended by an umbilical cable from their ship, The Performer. The ROV transmitted video images and other data to the mother ship where the scientists studied and analysed them.

The scientists have pieced together the sequence of the events of December 26, 2004. At 7.58 a.m., 20 miles below the ocean surface, the geological forces reached the breaking point. The fault started to rupture. The western side of the undersea mountain range on the edge of the plate was thrusted up by as much as 40 feet.

At twice the speed of a bullet, the plates unzipped over a distance of more than 750 miles lifting the seabed and the entire ocean above. On the surface, the displaced water moved out as a series of giant ripples causing tsunami.

200 trillion tonnes of water

Only 10 feet high but a hundred miles from front to back, the tsunami wave contained 200 trillion tonnes of water. It travelled at over 500 miles an hour. As it neared coasts and entered shallow water, the wave slowed but its back, a hundred miles behind was still travelling fast.

The rear end caught up, compressing the wave into a vertical wall of water upto 120 feet high.

The wave picked up tonnes of rock and sand from the sea floor. It hit Banda Aceh with the force of 60 hurricanes, destroying everything in its path, 25 minutes later at 9.50 a.m. a 60-feet wave crashed into Thailand and 45 minutes it engulfed the island of Phi Phi.

At the same time, the tsunami travelling west hit Tamil Nadu and Sri Lanka.

The deadly wave had travelled around the world thrice before expending its energy fully.

Map of terrain

The vast undersea mountainous terrain of the fault line encompasses 66,000 square miles. The team used specially developed compressed seismic guns to create a map of the terrain around the fault line.

Dr. Ingole analysed the earth samples brought up by the ROV to trace the presence of any biological activities. Their presence and type could determine the age of the site.

The absence of organism or the presence of fragile and short-lived ones proved that the crack and other evidence detected on the seabed were the result of the massive earthquake.

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