Actualité à la Une
13 January 2011
LONDON (AlertNet) - As Haiti marks one year since the devastating earthquake that killed as many as 300,000 people and toppled nearly 190,000 homes, a geologist at a leading research centre on natural hazards has warned it may be only the first of several earthquakes to strike the south of the country this century.
Simon Day, an expert in tsunamis and landslides with the Aon Benfield Hazard Research Centre, based at University College London, said analysis shows most of the ruptures that caused the 7.0 magnitude quake on January 12 last year did not take place as was initially thought on the main fault - the Enriquillo-Plantain Garden (EPG) Fault – which runs east-west, just to the south of the capital Port-au-Prince. While the temblor may have begun here, it consisted largely of a sequence of ruptures on other buried faults either side of the EPG Fault.
That suggests that the 2010 earthquake relieved little of the stress that has built up on that key fault since two major earthquakes in 1751 and 1770, which demolished much of Port-au-Prince. Consequently, further large quakes are a “very real possibility”, Day said.
“We can’t say there is going to be an imminent earthquake, but the point is that this is a seismically active region, and there is a hint in the historical data that quake activity in Haiti is clustered,” he told AlertNet.
“What is very clear from the aftershocks and land deformation (of last year’s earthquake) is that...the segment to the south (of Port-au-Prince) that moved in 1770 still hasn’t moved... It has been accumulating (land) deformation for 240 years, and that is a cause for considerable concern.”
Day’s comments are derived from evidence published in a series of studies in the November 2010 issue of the journal Nature Geoscience.
Among them, a team of scientists led by U.S. Geological Survey (USGS) scientist Carol Prentice, which visited Haiti right after the quake, found that the EPG Fault did not rupture the earth’s surface in January 2010, releasing little, if any, of the strain on that fault, which is a tectonic plate boundary between the Caribbean and North America plates.
On average, the plates slip around 2 cm per year, but since 1770, the two faults separating them have barely moved, causing elastic energy to accumulate on this part of the boundary.
This had led U.S. geologists to warn in 2008 that a big quake could be on the way – but they said they had no idea of predicting when it would be.
NEED FOR QUAKE-RESISTANT BUILDINGS
Day said the message for Haitian policy makers and the international aid community, working on plans to reconstruct the shattered capital and areas to the west, is to ensure that buildings are designed and built to withstand earthquakes.
“They need to be really serious about putting in the effort to make sure that whatever buildings are built back can resist future quakes, because it is very, very clear that within the life of a lot of the building stock they are going to build back, it will experience a seismic shaking comparable to what we saw in the city last year,” he said.
On Tuesday, the USGS said the 2010 Haiti quake - which accounted for almost all the fatalities from the 22 magnitude-7 or larger earthquakes that occurred in the world last year - resulted in catastrophe because of a high level of violent shaking, which can damage even well-built buildings, combined with buildings vulnerable to earthquakes and high population exposure.
Before the quake, Haiti’s sprawling capital was littered with shoddy buildings resulting from poor construction standards and inadequate building regulations. Many homes were built on steep slopes and unstable foundations.
Xavier Genot, who coordinates shelter activities for the Red Cross in Haiti, told AlertNet that bad building practices were common in the impoverished island nation, including inferior mixes for concrete and mortar.
“Not a lot of buildings in Haiti are quake-proof, except perhaps the American embassy,” he said, adding that it would be impossible to rebuild the capital to standards enforced in wealthy countries, or to strengthen all existing buildings, a process known as retro-fitting.
But he noted that efforts have been launched, under the guidance of the Haitian ministry for public works, to carry out repairs on tens of thousands of homes that were not too badly damaged by the quake, following a structural assessment of nearly 350,000 residences.
Local masons, engineers and construction firms are being trained, with the help of California-based structural engineering firm Miyamoto and aid agencies, to implement the work. So far, however, just 1,000 houses have been completed.
“It is not possible to retro-fit all of Haiti, but (the aim is) to improve capacity to allow for better repairs and to strengthen human resources for construction,” Genot said.
He added that the repairs, which have to be done by certified tradesmen, include replacing and reinforcing walls with stronger concrete blocks and mortar, and putting in new columns, in line with guidelines issued by the government.
According to a report issued by the International Federation of the Red Cross and Red Crescent Societies which documents progress a year after the earthquake, one innovative reconstruction prototype now under development, known as the gabion house, uses rubble encased in cages as building blocks, and is being assessed for its resistance to earthquake and hurricanes, another major hazard for Haitians.
Techniques like this could perhaps help address one of the major reasons why rebuilding of homes in the capital has been slow to start - the huge amounts of rubble piled up in the streets since the quake.
Figures from the United Nations Office for the Coordination of Humanitarian Affairs indicate that only 10-15 percent of more than 10 million cubic metres of rubble has been cleared away, although plans have been approved to step up this challenging task.
INFORM THE PUBLIC
The International Organisation for Migration (IOM) says 810,000 people are still living in informal sites in Port-au-Prince and the provinces - nearly half last July’s figure of an estimated 1.5 million internally displaced Haitians.
The inter-governmental agency knows the whereabouts of around 200,000 people who have left the camps for transitional shelters, returned to damaged or rebuilt homes, or gone to live elsewhere with assistance. But in a statement this week, it noted that issues over land tenure, uncleared rubble and the lack of land preparation for construction, together with environmental concerns and the need for risk mapping, are blocking more significant progress in resolving homelessness.
International aid agencies have built close to 32,000 transitional shelters, which are intended to house families for around three to five years.
The IOM has built 3,000 of the 8,000 temporary homes it plans to construct, selecting their location carefully to reduce the risk of hazards, and using materials like plywood and concrete board for the walls, which are designed to avoid major injury in the event of another earthquake.
Meanwhile, Genot of the Red Cross said the reconstruction of permanent homes from scratch has yet to get under way, and will require a clear urban planning strategy as well as the introduction of a building code.
Geologist Day called for a public education programme to inform people of the seismic risks new buildings will be exposed to - “if not in their lifetime, then in their children’s” - so they can participate in deciding what measures should be taken to make them safer.
“What would be tragic would be if they built the place back with the same low standards of building construction. The consequences would be similar to the last (earthquake),” he said.
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