Haiti may be at risk for more earthquakes, scientists say

The January earthquake that left Haiti in ruins and killed more than 200,000 people may not have had been the "big one" and almost certainly wasn't the last one.

New studies published Sunday point to a previously unmapped "blind" fault as the likely trigger for the catastrophe nine months ago and found no evidence it had eased more than two centuries of increasing seismic strain along the island's major pressure point, which geologists call the Enriquillo-Plantain Garden fault zone.

If anything, the studies conclude, Haiti now faces a heightened risk of repeat quakes along the Enriquillo fault — particularly near the heavily damaged, densely populated capital of Port-au-Prince.

"Even if this earthquake did not occur along the entire fault, it's certainly an indication that stress has built up in the area," said Andrew Freed, a Purdue University geophysicist and co-author of one of several papers published online in Nature Geoscience. "It's locked and loaded. My concern is that we are in the beginning of new cycles of earthquakes."

What scientists stress they can't pinpoint with any certainity is when or how frequently temblors might again shake the devastated country. Before the Jan. 12 quake, which measured 7.0 on the Richter scale, Haiti was last rocked by significant earthquakes in 1751 and 1770.

But University of Miami earthquake expert Timothy Dixon, who co-authored another study in the journal, said the series of quakes in similar "strike-slip" fault zones in places like Sumatra and Turkey strongly suggest it won't take centuries for the next big quake.

Typically, he said, other large quakes follow within decades and at either end of the fault zone, where earlier quakes can increase tensions between massive, slow-moving tectonic plates. The sudden, violent shifts that finally relieve that strain are what generate the intense shaking of an earthquake.

"There is another shoe waiting to drop at one or both ends of the rupture zone," said Dixon, a professor of geophysics at UM's Rosenstiel School of Marine and Atmospheric Science. "We can't say very much about when that other shoe will drop. It could be 100 years from now or it could be next month."

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