Quake Left Huge Ruptures in Seabed
Sonar Images Show How Tectonic Plates Folded Like Carpet
By CHRISTOPHER BODEEN, AP
BANDA ACEH, Indonesia (Feb. 10) - The first images Thursday of the seabed battered by the earthquake that triggered Asia's catastrophic tsunami revealed huge ruptures spanning several miles.
A British naval ship collecting data off the coast of Indonesia's Sumatra Island produced the digital images using sonar, and they could be used to help develop a tsunami early-warning system for the Indian Ocean region.
The vibrantly colored seabed maps show the 9.0-magnitude quake caused the tectonic plates to clash ''like the rumpling up of a carpet,'' according to Steve Malcolm, the commanding officer of the HMS Scott.
The images show ''scars'' more than six miles wide resulting from the Dec. 26 quake. They depict the line where the Indian tectonic plate suddenly collided with, and was pushed underneath, the Burma plate.
The maps, created with multi-beam sonar, show ridges as tall as 4,950 feet that were created over thousands of years by the slow collision of the deep, flat Indian plate and the ragged edge of the Burma plate.
That collision has resulted in the Indian plate being gradually shoved under the edge of the Burma plate in a process known as subduction, said Russell Wynn, a marine geologist at the Southampton Oceanography Centre, which took part in the survey.
The Dec. 26 quake was caused by a sudden movement of the two plates, which in turn caused the ridge of the Burma plate to spring up about 30 to 60 feet, Wynn said. That sent water surging up and out, creating the devastating waves that menaced the region. The main collision zone was some 12,000 feet below the ocean surface.
Wynn said scars seen on the digital images were likely landslides created by sediment being loosened by the earthquake.
The epicenter of the earthquake was 24 miles below the seafloor, Wynn said.
Scientists from the Southampton Oceanography Centre in southern England and the British Geological Survey have been working with the crew on the HMS Scott since Jan. 26. It was the first time the seafloor has been observed so soon after an earthquake of such a scale, the team said.
The images show deep areas in dark purple and blue, and the high ridges caused by the slow plate collision in green, yellow and red. The images were on display at the U.K. Hydrographic Office in Taunton, southwest England, and on the body's official Web site.
President Bush, meanwhile, said Thursday he would ask Congress for $950 million for tsunami relief efforts - up from $350 million committed so far. The pledge would put the United States at the top of the list of donors for the disaster.
''We will use these resources to provide assistance and to work with the affected nations on rebuilding vital infrastructure that re-energizes economies and strengthens societies,'' Bush said in a statement.
The difficult task of recovering the dead in Indonesia is unlikely to be finished by June as corpses continue to be found in the rubble, said Yrsa Grune from the International Federation of Red Cross and Red Crescent Societies.
Volunteers have been helping a government-led effort to collect and bury victims in Aceh.
Indonesian officials have said they expect the death toll to rise for weeks by an average of 500 a day, but Grune said the search could stretch on for months.
''The plan was to continue until June. Now, it might be that plan will have to be revised,'' she said. ''It's inevitable. Every time you lift a stone you might find something under it because there's still lots of rubble.''
Hundreds of residents of Banda Aceh remembered the victims of the disaster during a memorial service Thursday on the Islamic New Year.
''This is a trial from God, an opportunity for the Islamic community in Aceh to reflect on their lives,'' the province's vice governor, Azwar Abubakar, said in an address broadcast over loudspeakers at the 17th century Baiturrahman Mosque, where many sought shelter from the disaster.
''Let us draw closer in brotherhood,'' Abubakar said. ''Let us gather together to do good deeds and reject sin.''
Aftershocks have rattled the region since the Dec. 26 quake that spawned the tsunami, killing more than 160,000 people in 11 Indian Ocean nations. Tens of thousands of people are still missing, though officials say it's too early to add them to the toll.
