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Haiti threatened by a new earthquake
samedi 23 janvier 2010
Haiti threatened by a new earthquake
The seismologs insist on the necessity of rebuilding according to strict standards.
(Reuters)
A so strong earthquake, even more powerful than the one who destroyed Port-au-Prince, threatens the Haitian capital at any time, warn the seismologs, insisting on the necessity of rebuilding according to standards strict as in California or in Japan.
Haiti, where retorts are smelt since the earthquake of magnitude 7 of January 12th, will remain exposed hanging Several weeks At a risk importing strong secondary shocks, a usual phenomenon after all earthquake, which is going to become blurred in time.
The American geologic Institute ( USGS) estimated on Thursday at 25 % the probability of one or several retorts of intensity 6 during this period.
But if the recent earthquake freed a big part of the tension accumulated on this part of her Fault Enriquillo, It seems that another portion, east of the epicentre and directly neighboring to Port-au-Prince, than little moved, according to the USGS.
The geologic institute leans on preliminary measures of deformation of the ground made with radars and aerial views.
According to the USGS, this part of the fault underwent the same accumulation of tension under the influence of the coulissement of the tectonic patches North American and the Caribs, and risk at any time to free this energy.
" The previous earthquakes in the world and the seismic history of Haiti indicate us that earthquakes of big amplitude can sometimes occur (in the same place) for the period moved closer ", explain to AFP David Schwartz, An expert of the USGS.
Quoting the case of Turkey in 1999, when two earthquakes exceeding the magnitude 7 took place in three months of interval, David Schwartz considers that the same scenario could repeat in Port-au-Prince. " None of us would be surprised ", adds the seismolog.
Region at risks
The fault of Enriquillo can again provoke a shock reaching a magnitude 7,2, judges for its part Eric Calais, A French seismolog of the University Purdue, in the Indiana (the North of the United States).
" Earthquakes in this region tend to repeat in sequence ", he raises, reminding that during the last three centuries, earthquakes of amplitude comparable or superior to that of January 12th shook Haiti at least on four occasions, among which those of 1751 and 1770 who destroyed Port-au-Prince.
" If the region has a past of recurring earthquakes, it is necessary to reconstruct Port-au-Prince according to strict seismic standards ", warns Eric Calais. " There will be an additional cost but technically no problem ", he underlines, noting that " we build nuclear power stations capable of resisting to magnitude 8 ".
A detailed evaluation of the seismic risk in Haiti, the poorest country of Americas, and in other countries of the Caribs, will allow to improve the standards of construction to build buildings resisting to earthquakes, explains the USGS in its last bulletin. But it requires detailed geologic studies of the faults and the ground, which set generally several years, according to the USGS.
Eric Calais regrets the fact that Haiti was until now Neglected in this domain. Only two teams of geologists and seismologs, whom his, went in Haiti these last fifteen years and had moreover warned against the risk of a new important earthquake.
On Monday, this seismolog has to go in Haiti with a battery of instruments to coordinate a mission of study, the spot first one since the disaster of January 12th.
( Nouvelobs.com, with AFP)