This year’s devastating earthquake
in Haiti was caused by a previously unknown fault, according to scientists.
This discovery, the researchers
say, could be the first sign of a larger system of seismic faults in the area.
The Enriquillo fault, which runs
through Port au Prince, was originally blamed. But new evidence has shown that
it was not linked to the event. Eric Calais from Purdue University in Indiana
presented the findings at a scientific meeting in Brazil.
The earthquake in Haiti had no
bearings on a smaller earthquake a week later on Grand Cayman and several small
tremors in the following weeks.
Grand Cayman lies just to the north
of the Oriente Fracture Zone. The active fault line runs along southeast coast
of Cuba to an area just west of Cayman, roughly following the northern edge of
the Cayman Trough.
Over the course of recorded
history, there have been a number of powerful earthquakes along the Oriente
Fracture Zone, but only the ones near Santiago de Cuba are known to have caused
severe damage and deaths.
In Brazil at the American
Geophysical Union’s Meeting of the Americas in Foz do Iguacu, Calais explained
that the Haiti earthquake was more complicated than previously thought.
He said that the first “give-away”
was the fact that there was no surface break along the known Enriquillo fault.
This led to a search for other faults or fractures in the Earth’s crust, which
may have slipped and caused the event.
The earthquake in January killed
more than 200,000 people and left 1.5 million homeless. Amid the devastation,
it took scientists several months to gather data about what really shifted the
Using techniques including GPS and
radar, Mr. Calais and his colleagues were able to show that the “pattern of
motion was incompatible with slippage on a vertical fault such as the
Further calculations showed that
the only way to fit the observations was by mapping the slip to a fault that
was slightly oblique to the Enriquillo and dipped 60 degrees to the north.
This previously unmapped fault was
only brought to scientists’ attention by the earthquake itself – it may be one
part of a larger system of seismic faults.
Mr. Calais told BBC News that
searching for and studying this system was crucial in order 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 said.
“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.”