Quake behind Asian tsunami was longest on record

LONDON - The earthquake that triggered the devastating Boxing Day tsunami was the longest on record - extending over 1200 km - but poses little further immediate danger, scientists said.

However, large earthquakes and possible giant tidal waves are a threat on the segments of the tectonic plate boundary to the south, they wrote in the science journal Nature in papers penned well before this week's major quake in the danger zone.

The December 26 subsea earthquake off northern Indonesia measuring 9.0 on the open ended Richter scale triggered a tidal wave that swept across the Indian Ocean spreading death and devastation from Sri Lanka to Thailand.

Three months after the disaster, nearly 300,000 people are still missing or known to be dead, and more than one million are homeless.

The two groups of scientists working independently at Northwestern University in the United States and the University of Science and Technology of China both reached the same conclusions on the size of the rupture.

They said the size of the quake was far bigger than previously estimated and had the odd characteristic of having had a long, slow slip in the northern end of the giant fault followed by a sharp rapid move in the southern section.

"We determine the rupture length to be 1200 km -- the longest ever recorded," wrote the team from Anhui in China, noting that the quake lasted more than eight minutes at its peak power.

The team from Illinois said the odd characteristics of the earthquake and its extent made a repeat unlikely in the near future.

"Strain accumulated on the northern part of the rupture has been released. There is therefore no immediate threat of an oceanwide tsunami being generated ... because such earthquakes should be at least 400 years apart," they wrote.

"However, the danger of a large tsunami resulting from a great earthquake on segments to the south remains," they added.

The article appeared just two days after the major earthquake measuring 8.7 struck some 200 km south of the epicentre of the December quake.

Although there was no repeat of the giant tsunami, the March 28 earthquake killed an estimated 1,000 people and devastated coastal communities in northern Indonesia still struggling to rebuild three months after the Boxing Day wave.

- REUTERS