Massive quake for Sumatra was predicted less than two weeks ago
PARIS (AFP) - With eerie precision, seismologists warned less than two weeks ago that Sumatra was at imminent risk of being hit by a quake of roughly the same magnitude that struck the Indonesian island.
In a study published on March 17, a British team said there was "potential" for a massive early temblor in the ocean floor west of Sumatra as a result of tensions stoked up there by the December 26 quake.
They said the quake could be as powerful as 8.5, and possibly generate a tsunami.
"There is no doubt -- our calculations show a very significant increase on stress on two major active faults in the Sumatra region," seismologist John McCloskey at Britain's University of Ulster told AFP in an interview on March 15.
"We are not trying to cry wolf," said McCloskey. "We can point to many other quakes where the stresses like the one we've measured have resulted in a following earthquake, and we are suggesting there is a significantly increased risk."
He added: "When it comes to earthquakes, lightning does strike twice."
McCloskey said that the indicators of an early, powerful quake in the Sumatra region were very strong, but admitted that no-one could tell exactly when such an event would occur.
But his warning was exceptional. It was as close as it gets to a prediction in a science whose practitioners are notoriously cautious about false alarms.
McCloskey explained that in so-called subduction zones, an earthquake can be swiftly followed by another one if certain geological conditions are met.
"There is a very well-established link between these stresses and following earthquakes," he said.
Energy released by the December 26 9.0-magnitude quake had boosted stress in adjoining parts of two dangerous faults, he said.
One fault runs under land to the east of the quake region and crosses the northwestern tip of Sumatra, running under the city of Banda Aceh, the capital of the Indonesian province that was badly hit by that event.
Banda Aceh was in fact rocked by a 5.9-magnitude quake last Friday.
The other fault, known as the Sunda Trench, runs under the sea to the south, parallel to the Sumatra coast, where two fatal tsunamis occurred in 1833 and 1861.
The December 26 movement ruptured 250,000 square kilometers (96,500 sq. miles) on a stretch of the Burma microplate, a narrow tongue of the Earth's crust that is jostled by the neighbouring Indian, Australian and Sunda plates.
That seabed plunge, by as much as 20 metres (65 feet), triggered the tsunami, killing more than 273,000 people in 11 nations on the northern rim of the Indian Ocean.
Part of the energy released by the quake was transferred to the contiguous fault sections. It distorted, compressed and deformed the rock, adding to the burden at known stress points and creating new ones.