Haiti

FACTBOX-Haiti quake had shallow source, packed big punch

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Jan 13 (Reuters) - The 7.0 magnitude earthquake that struck Haiti on Tuesday, toppling buildings and killing possibly thousands, was the most powerful to hit the impoverished Caribbean state in more than a century.

Here are comments from international seismologists about the Haiti quake:

DR DAVID ROTHERY, PLANETARY SCIENTIST AT BRITAIN'S OPEN UNIVERSITY:

"The earthquake that struck Haiti yesterday was so devastating because as well as being large (magnitude 7.0) its source was at a shallow depth of about 10 km (6 miles). Closeness to the surface is a major factor contributing to the severity of ground shaking caused by an earthquake of any given magnitude. Furthermore, shaking tends to be greatest directly above the source. In this case the epicenter was only 15 km (9 miles) from the center of the capital, Port-au-Prince, which therefore suffered very heavily.

MICHAEL BLANPIED, ASSOCIATE COORDINATOR FOR THE U.S. GEOLOGICAL SURVEY EARTHQUAKE HAZARDS PROGRAM:

"The island of Hispaniola -- and Haiti lies on the western side of the island -- is caught between two tectonic plates. The North American and the Caribbean tectonic plates are shearing the island, crushing it, grinding it and as that occurs, earthquakes pop off. The island has not suffered an earthquake of this size for over a century".

"Earthquakes cause disturbance of the ground in a number of different ways. Wherever there are steep slopes or coastal areas there's likely to be landsliding and that can bury homes, or block streams, rivers, block roads and so forth, so there's a hazard. The only positive thing about this earthquake is that because it did occur on land it did not generate a tsunami."

DR ROGER MUSSON, SEISMOLOGIST AT THE BRITISH GEOLOGICAL SURVEY:

"The situation in Haiti is similar to the San Andreas Fault in California in that two plates are sliding past one another. The fault in this case is called the Enriquillo-Plantain Garden fault. This fault has been locked for the last 250 years gradually accumulating stress which has now been released in a single large earthquake."

PROFESSOR ROGER SEARLE FROM THE EARTH SCIENCES DEPARTMENT AT DURHAM UNIVERSITY IN BRITAIN:

"This quake was magnitude 7, equivalent to the energy release of about half a megaton of TNT ... To date (1400 GMT Jan 13) the USGS has recorded 33 aftershocks greater than magnitude 4.5 (large enough to cause at least minor damage).

DR BRIAN BAPTIE, SEISMOLOGIST OF THE BRITISH GEOLOGICAL SURVEY:

"Earthquakes of this size always have aftershocks that can last for many weeks. These always punch above their weight, affecting buildings that have already been damaged and hampering relief efforts."

Sources: U.S. Geological Survey (USGS), London-based Science Media Centre (Reporting by Kate Kelland and Pascal Fletcher; Editing by Jane Sutton and David Storey)

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