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THONY BELIZAIRE  /  AFP - Getty Images
A UN soldier patrols next to a destroyed building on January 20, 2010 in Port-au-Prince. A 5.9-magnitude aftershock rattled Haiti on Wednesday, and scientists say more may be coming.
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updated 1/20/2010 2:59:27 PM ET 2010-01-20T19:59:27

Haiti can expect more aftershocks in coming weeks, and while the usual pattern suggests they will become weaker and less frequent, another one as strong as Wednesday's jolt is certainly possible, scientists say.

The battered nation has felt more than 40 significant aftershocks since the Jan. 12 quake, with Wednesday's temblor the strongest. Originally estimated at magnitude 6.1, Wednesday's aftershock was later revised to a 5.9.

These events are a sign the land is adjusting to "the new reality of the rock layers," said Bruce Pressgrave, a geophysicist with the U.S. Geological Survey.

Eric Calais of Purdue University, who has studied earthquake potential in the region, said aftershocks could continue for several weeks and that another jolt as strong as Wednesday's would not be surprising.

"They will be less and less frequent, but large ones can still strike," he said. So buildings are still at risk, especially those already weakened, he said.

Julie Dutton, a USGS geophysicist, agreed that more aftershocks are probable and that another event like Wednesday's was certainly possible. "More likely we see that the earthquakes decrease in size, but you definitely have the potential that you can have a larger earthquake," she said.

Paul Mann of the University of Texas said it's hard to predict whether another sizable quake is in the future, since "we are dealing with a natural system that is very complex."

Calais also said the fault zone responsible for last week's quake extends into the neighboring nation, the Dominican Republic. It's "somewhat of a concern to us" that that the Haiti quake may have raised the chances for a quake there. The two countries share the island of Hispaniola.

But scientists don't know enough to make any forecasts, he said. "There is so much uncertainty," Calais said. "At this point we're working really hard to understand last week's earthquake, and from there we can perhaps understand what might happen next."

Mann said Haiti's disaster should not raise the risk of earthquakes throughout the wider Caribbean region. The area is seismically active anyway, he said, and people who feel a temblor shouldn't assume it's a reaction to last week's Haiti quake.

For people living well away from Haiti, such as in Trinidad, Venezuela, Colombia or Central America, "I don't think they should be fearful that the Haiti earthquake is going to activate a fault in their own back yard," Mann said.

Associated Press editor Lori Hinnant in New York contributed to this report.

Copyright 2010 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

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