Grinding poverty and tectonic volatility make a devastating combination.

 

In Port-au-Prince, which has some of the largest slums in the world, even the best constructed buildings have reportedly collapsed, suggesting that the sprawling, densely populated hillside slums would be devastated .

“With major buildings destroyed it is likely that less well-constructed homes will be even more seriously affected. The island has not yet recovered, let alone been able to protect itself ­properly,” said an Oxfam spokeswoman today. “That construction is a recipe for disaster when an earthquake strikes,” said Kate Hutton, a seismologist with the Massachusetts Institute of ­Technology. “This is an area that is particularly vulnerable in terms of construction practice.”

The geological conditions in Haiti are similar to those at the San Andreas fault in California, where two tectonic plates are sliding past each other. The Enriquillo-Plantain Garden fault has been accumulating stress for more than two centuries and this energy has now been released in a very large, magnitude seven earthquake.

In addition to being large, the quake was at a shallow depth – six miles (10km). “Closeness to the surface is a major factor contributing to the severity of ground shaking caused by an earthquake of any given magnitude,” said David Rothery, a planetary scientist at the Open University.

“Shaking tends to be greatest directly above the source. In this case the epicentre was only nine miles (15km) from the centre of the capital, Port-au-Prince. From the pictures I have seen, and from what I know of Haiti’s impoverished economy, I doubt if buildings there have been constructed with earthquake resistance in mind. They are at risk of further collapse caused by aftershocks, of which there have been several strong ones. The debris in the streets suggests that people would have been killed or injured by falling masonry if they tried to flee buildings while the ground was shaking, rather than sheltering under a table until motion had ceased.

“It is many decades since a comparably strong quake has hit Haiti, and I wonder if the population was adequately aware of what they could do to protect themselves,” he said.

The north Caribbean Islands are not frequently hit by large earthquakes. This one was caused by a sideways slip on a fault that marks part of the northern edge of the Caribbean plate grinding against the North American plate.

Further to the east the plate boundary changes direction and becomes a subduction zone that is the cause of the volcanoes of the Caribbean arc, including the erupting Soufriere Hills volcano on Montserrat. David Kerridge, head of earth hazards at the British Geological Survey, said that with a big earthquake in mountainous terrain there was a strong possibility of landslides, which could cause many casualties in more remote parts. “Due to disruptions in communications the extent of the disaster might not be clear for a few days.”

Deadly decades

1963 Hurricane Flora kills 8,000 Haitians

1986 Duvalier dictatorship falls, ­destabilising the country

1998 Hurricane Gordon causes mudslides that kill almost 1,000 residents

2004 Flooding from Hurricane Jeanne leads to 3,000 deaths

2004 Military coup drives out former president Jean-Bertrand Aristide

2008 Hurricanes Fay, Gustav, Hanna and Ike strike, leaving 1,100 people dead or missing and causing $1bn worth of damage

2008 Food riots in Port-au-Prince

2008 School building collapses in Pétionville, killing nearly 100

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