PARIS - The Chile earthquake released nearly 1,000 times more energy than the one that devastated Haiti in January, but left 200 times fewer fatalities. While rescue teams sift through the rubble, experts said many factors explained the difference between the 723 dead so far in Chile while the tally in Haiti has topped 220,000.

An earthquake's magnitude reflects the amount of seismic energy released at its epicenter, usually the meeting point of tectonic plates pushing up against or pulling away from each other.

The Haiti quake, which struck on January 12, measured 7.0 in magnitude, while the one in Chile, at 8.8, was nearly two orders of magnitude greater. Each notch on the scale represents a 10-fold increase in amplitude, or the degree of shaking of the ground, and a more than 30-fold jump in the amount of energy released.

"But there is no direct link between magnitude and its deadliness or level of destruction of human habitat," said Robin Lacassin, a seismologist at the Institute Physique de Globe in Paris.

Some 15 to 20 quakes every year top magnitude 7.0, but most go unnoticed except by scientists because they occur in the ocean or unpopulated areas. Both quakes occurred near large cities, so other factors account for the difference.

"The earthquake near Port au Prince was very shallow, only about 15 kilometers (9 miles) below the surface," compared to about 35 kilometers below the ocean floor for Chile, Lacassin said. But proximity alone did not account for the massive destruction of huge loss of life in January, he and other experts pointed out.

"The quality of construction and building codes in Haiti were obviously not as strong as those in Chile," said David Galloway, a seismologist at the British Geological Survey.

AGENCE FRANCE- PRESSE

(China Daily 03/03/2010 page11)