Friday, January 15th 2010 - 09:40 UTC

Haiti sits on two seismic fault lines and a major disaster was expected

Seismologists have known for years that a devastating earthquake was likely to hit Haiti. They just did not know when. Although Tuesday’s devastation was wreaked by the most severe quake to hit Port-au-Prince since 1751, the island has been the victim of major seismic activity several times since.

The 7.0 quake deadly shock waves were equivalent to the force of 35 Hiroshima nuclear bombs and flattened Port-au-prince

In 1946, a severe tremor in the region triggered a tsunami in the neighbouring Dominican Republic that killed almost 2,000 people. But what made the consequences of this week’s earthquake so much worse than previous ones was that it happened only 8km below the surface and only 15km from the Haitian capital.

The problem in geological terms is that the Haitian half of the island of Hispaniola sits sandwiched between two fault lines on the divide between the North American tectonic plate and the Caribbean plate.

Seismologists estimate that the Caribbean plate is heading eastward at a rate estimated at between seven and 20mm a year – a seemingly miniscule amount but enough to produce tremendous pressures building up beneath the earth’s crust as these vast slabs grind against each other.

This movement has produced two fault lines, called strike-slip faults, to the north and south of Haiti: the Septentrional fault in the north and the Enriquillo-Plaintain Garden fault, which caused Tuesday’s disaster.

“It’s been locked solid for about the last 250 years,” said Roger Musson, a seismologist from the British Geological Survey.

“It’s been gathering stress all that time as the plates move past each other and it was really just a matter of time before it released all that energy. The question was going to be whether it would release it all at once or in a series of smaller earthquakes.”

That question was answered at 21.53 GMT on Tuesday when the quake measuring 7.0 on the Richter scale sent its deadly shock waves – equivalent to the force of 35 Hiroshima nuclear bombs, according to scientists – through the streets and shantytowns of Port-au-Prince.

Although there have been more powerful quakes in Haiti’s history, the most recent measuring 7.2 in 1887, the fact that this one was comparatively shallow in the ground meant that its power was scarcely dissipated by the time it reached the surface.

Its closeness to Port-au-Prince also meant that extensive loss of life was inevitable in a city of more than a million souls, the vast bulk of them crowded together, often on hillsides, in a country where there is neither the money nor expertise to construct buildings capable of withstanding severe tremors.

Haiti’s plight has been made worse by the fact that only 3% of the island remains as forest. When Europeans first arrived there 500 years ago, they marvelled at the density of the trees, but subsequent deforestation, mainly to make charcoal, has left the terrain bare and vulnerable to landslides.

David Rothery, a planetary scientist at the UK’s Open University, said: “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.”

It proved to be this combination of natural disaster allied to man-made failings that has led to such a dreadful loss of life in Haiti. Last year, the US Geological Survey recorded 17 earthquakes of magnitude 7.0 or greater, but none wrought the devastation now being experienced in Port-au-Prince.

Professor Roger Searle from the Earth Sciences Department at Durham University said the quake was equivalent to the energy release of about half a megaton of TNT. Earthquakes of this size can cause relatively slight damage in well-designed and constructed buildings, but considerable destruction in poor ones.

”The last major earthquake in this part of Haiti was 1860; in 1692, a major earthquake in Jamaica caused 2,000 deaths. To date the United States Geological Survey has recorded 33 aftershocks greater than magnitude 4.5 (large enough to cause at least minor damage)”, said Professor Searle.

6 comments Feed

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1 Y Whitfield (#) Jan 16th, 2010 - 09:51 am Report abuse
How can Haiti be flattened and the neighboring country, Dominican Republic, not have any major devastation in its lands? An earthquake of 7 on the Richter Scale (10,000,000 in magnitude), occuring 8km from the surface and 15km from Portia Prince, is too massive too be absorbed by little Haiti. Logically, some damage should be evident at least near the border of the two neighboring countries.

Did someone release some nuclear weapons underground around and near Haiti? Come on, get real.
2 Ramonn (#) Jan 22nd, 2010 - 12:33 pm Report abuse
Well in my opinion that no one can be blame for this natural disaster, it happened and it will keep happening again. I know this will sound hard but in my opinion again, i believed that the people from Haiti should think about leaving Haiti for good and migrate on another island or country called New Haiti some where far away from tectonic plates area. More than 100K people died on this 7.0 earthquake imagin if it was higher. I know Haitian love there island but i think its time to move foward and grow strong and take this apportunity that the WORLD want to help and change for better!!!!! In Another Area!!!!!
3 jimmie johnson (#) Jan 22nd, 2010 - 12:54 pm Report abuse
Well actually, George W. Bush hates black people so he had bombs placed under the capitol before he left office so he could have the last laugh......
Don't you guys get tired of these stupid theories about why these things happen?
4 Erika (#) Jan 22nd, 2010 - 02:42 pm Report abuse
I lived in the Dominican Republic for a year and a half. Any type of natural disaster on that island would be devastating no matter where it occurred. The devastation is huge because they don't have building codes and many of the homes are just shacks sometimes made out of rolled out cans. My heart just breaks for the Hatians. They can't just leave. They don't have the resources. They are the most humble people I have ever been privileged to meet. I am certain that there was quite a bit of damage in the Dominican Republic and may not have been reported due to the fact that they aren't as poor as Haiti. What I know of Hatians is this though, they will rebuild and they will come through. They are strong people!
5 whyman (#) Jan 22nd, 2010 - 02:50 pm Report abuse
Why is the poorest inhabitants of the earth are always the ones that the mountains fall on, volcanos erupt on, hurricanes blow on, famine struck on, dictators brutalize on, even though they are the ones that readily acknowledges a divine power. The inhabitants who are not as poor, and who do not share the beliefs of the poor are not touched................Why ???
6 Annie (#) Jan 27th, 2010 - 05:17 am Report abuse
Maybe now that petroleum and natural gas are seeping up from the earth's mantle Haiti can be on it's way to becoming the next Kuwait and develop economical stability in the only nation to gain independence by a slave-led rebellion, the first black republic, and the second oldest republic in the western hemisphere.

That may be the only silver lining in such a devastating, senseless and heart wrenching situation.

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