August 12, 2010

Previously Unknown Fault Caused Haitian Earthquake

Scientists say the earthquake that took place in Haiti was caused by a previously unknown fault.

The researchers say that this discovery could be the first sign of a larger system of seismic faults in the area. 

The fault that runs through Port au Prince, which is also known as the Enriquillo fault, was originally blamed for the earthquake.

Eric Calais presented the findings at the American Geophysical Union's Meeting of the Americas in Foz do Iguacu, Brazil.  He explained that the earthquake was more complicated than previously thought.

He said the first evidence of the fault was the fact that there was no surface break along the Enriquillo fault.  This discovery led the researchers to find other faults or fractures in the Earth's crust, which may have slipped and caused the devastating event in Haiti.

The Haitian earthquake took over 200,000 people's lives and left 1.5 million people homeless.  It took scientists several months to gather data about what really shifted the ground.

Calais, from Purdue University in Indiana, and colleagues used techniques like GPS and radar to show that the "pattern of motion was incompatible with slippage on a vertical fault such as the Enriquillo."

After performing more calculations, the researchers saw that the only way to fit the discovery was to map the slip to a fault that was slightly oblique to the Enriquillo and dipped 60 degrees to the north.

Calais told BBC News that studying this system was crucial when trying to define "the long-term hazard level in Haiti."

"Fault slippage during an earthquake alters the hazard level in the region in a way that depends on the fault location, geometry, and slippage," he told BBC.

"In some areas hazard will be slightly increased, in others it will be decreased. There is ongoing research on what the specific consequences might be for southern Haiti."


Image Caption: Damaged buildings in Port-au-Prince. Credit: Marco Dormino/The United Nations (Wikipedia)


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