Topography Along the Enriquillo-Plaintain Garden Fault, Haiti
Posted by JAC on 1/14/2010, 6:48 am
7.2 Predicted in 2006:

http://www.ig.utexas.edu/jsg/18_cgg/Mann3.htm

http://en.wikipedia.org/wiki/Enriquillo-Plantain_Garden_fault_system









At 4:53 p.m. local time on January 12, 2010, a 7.0-magnitude earthquake struck Hispaniola Island, just 15 kilometers (10 miles) southwest of the Haitian capital of Port-au-Prince.

http://www.cnn.com/video/data/2.0/video/world/2010/01/13/von.haiti.quake.aftermath.cnn.html

http://www.usatoday.com/news/world/2010-01-14-quake-interactive-map_N.htm?csp=34


Besides its strong magnitude, the earthquake's shallow depth of roughly 8.3 kilometers (5.2 miles) ensured that the densely populated capital suffered violent shaking.

The first map above shows the topography and tectonic influences in the region of the earthquake.

Lighter colors indicate higher elevation.

Black circles mark earthquake locations determined by the U.S. Geological Survey, and circle sizes correspond with quake magnitudes.

Red lines indicate fault lines.

Dozens of aftershocks followed the main quake.

http://earthquake.usgs.gov/earthquakes/recenteqsww/Maps/10/285_20_eqs.php






The epicenter of the quake appears just south of the Enriquillo-Plaintain Garden Fault, the southernmost of two major east-west-trending faults that bear the stress of the convergence of the Caribbean and North America tectonic plates in this location.

Though faults are weak spots or fractures in the Earth's crust below the surface, very often there are topographical clues to their presence.

In this case, the presence of the fault is indicated by long, straight valley cutting through southern Haiti, just south of Port-Au-Prince.

The Enriquillo-Plaintain Garden Fault is a strike-slip type fault, with the Caribbean plate moving eastward with respect to the North America plate.



Haiti quake was nightmare waiting to happen say scientists

Published on Thursday, January 14, 2010

By Richard Ingham

PARIS, France (AFP) -- The quake that hit Haiti on Tuesday was a killer that had massed its forces for a century and a half before unleashing them against a wretchedly poor country, turning buildings into death traps, experts said on Wednesday.

Scientists painted a tableau of horror, where natural forces, ignorance and grinding poverty had conspired to wreak a death toll tentatively estimated by Haitian Prime Minister Jean-Max Bellerive at more than 100,000.

The 7.0-magnitude quake occurred very close to the surface near the Haitian capital of Port-au-Prince, leaving almost no natural buffer to soften the powerful shockwave, these experts said.

"It was a very shallow earthquake, occurring at a depth of around 10 kilometers (6.2 miles)," seismologist Yann Klinger of the Institute of the Physics of the Globe (IPG) in Paris told AFP.

"Because the shock was so big and occurred at such a shallow depth, just below the city, the damage is bound to be very extensive," he said.

The US Geological Survey (USGS) said the quake occurred at 2153 GMT on Tuesday 15 kms (9.4 miles) southwest of Port-au-Prince.

It happened at a boundary where two mighty chunks of the Earth's crust, the Caribbean plate and the North America plate, rub and jostle in a sideways, east-west movement.

The USGS said the rupture occurred on the "Enriquillo-Plaintain Garden fault system," a slow-moving fault that last unleashed a large quake in 1860. Prior major events to that were in 1770, 1761, 1751, 1684, 1673 and 1618.

Sandy Steacey, director of the Environmental Science Research Institute at the University of Ulster in Northern Ireland, said the high death toll could be pinned overwhelmingly to construction.

"It's a very, very poor country without the building codes. Probably the fact that earthquakes (there) are very infrequent contributes in a way, because it's not a country that is focussed on seismic safety.

"Looking at the pictures, essentially it looks as if (the buildings are of) breeze-block or cinder-block construction, and what you need in an earthquake zone is metal bars that connect the blocks so that they stay together when they get shaken," said Steacey.

"In a wealthy country with good seismic building codes that are enforced, you would have some damage, but not very much."

French seismologist Pascal Bernard, also at the IPG, said that, given the nature of the fault, there was a "sizeable probability" that another large quake could occur in the same region within a matter of years.

Like other faults around the world, the Haitian crack is well known for domino activity, in which the release of pressure on one stretch piles on pressure in an adjoining stretch, bringing it closer to rupture.

In Haiti's case, the likeliest spot of a bust would be to the east of Tuesday's quake, Bernard said.

Asked whether another big quake was in the offing, Roger Searle, a professor of geophysics at Durham University, northeast England, said, "In the coming years, almost surely."

"We know pretty much where earthquakes occur, they've been mapped themselves and we can map faults and so on.

"The difficulty is it's very, very hard to predict when they will occur, because the network is so complex.

"It's a bit like making a pile of stones. You put more on the pile and it gets steeper and steeper and sooner or later the thing is going to collapse but you never which stone is going to do it and just where it's going to start to fail."



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Topography Along the Enriquillo-Plaintain Garden Fault, Haiti - JAC, 1/14/2010, 6:48 am
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