Researchers Return to Haiti to Gather Data; Previous Model Was a Close Fit to Haiti Quake

FAYETTEVILLE, Ark. – The devastating earthquake that took so many lives in Haiti had its origins in hundreds of years of plate movement, and geologists researching this movement are now studying the region to determine how this quake has changed the strain between plates – and what this might mean in terms of future tremors for Haiti and the surrounding islands.

A University of Arkansas researcher and his colleagues are traveling to Haiti as part of a National Science Foundation expedition to continue measurements and better understand what happened, what is happening now, and what might yet occur. The research team, led by Eric Calais of Purdue University and composed of scientists from the University of Arkansas, the University of Texas and the Haitian Bureau of Mines and Energy, has worked in the Caribbean for years, measuring and modeling slip rates and strain.

“Studies show that an earthquake of this magnitude can cause stress transfer to the same fault or nearby faults,” said Glen Mattioli, University of Arkansas professor of geosciences. Taking measurements from new and existing sites in Haiti and the Dominican Republic will help the researchers learn more about whether that stress exists and where it might be.

The Haiti earthquake took place along one of several microplates that occur within the boundary between the North American and Caribbean plates. In research conducted prior to the Haiti earthquake, Mattioli, professor of geosciences Pamela Jansma and their colleagues used global positioning satellite geodesy to monitor millimeter scale movements along the tectonic plates in the Caribbean basin to determine the motion between the plates. Using the data, they created a regional model that showed the slip rates and strain accumulation at various sites, and also included information on coupling, or sticking – which implies an elevated risk of earthquakes. This model suggested that the strain along the Enriquillo-Plantain Garden fault below Haiti had accumulated to a point where, if an earthquake were to occur, it would have a magnitude of about 7.2. They published these results in the 2008 Geophysical Journal International.

“The earthquake on this fault was only one manifestation of the ongoing deformation,” Mattioli said. “Unfortunately, there will be others and there are many millions of people at risk.”

The researchers had about 30 sites in Haiti and 35 sites in the Dominican Republic that they had used to monitor these small movements in the earth’s crust. The researchers plan to re-measure all the sites, although they suspect that some of the ones close to the epicenter of the quake may be lost or destroyed. The scientists also will install other sites to begin to measure post-seismic displacement. And they will install some continuous monitoring stations to examine visco-elastic relaxation, or the deformation of the lower crust and mantle that takes place after the earthquake. As the upper crust moves, it transfers energy to the lower crust and mantle.

“It’s another constraint that gives us more information about rupture displacement,” Mattioli said.

The accumulated knowledge can in turn be used to help communities in the Caribbean prepare for possible future tremors.

“Good science and engineering must be complemented by adequate preparation, appropriate policy regarding earthquake hazards and meaningful regulations regarding the design and construction of civil infrastructure,” the researchers said.

Mattioli is a professor of geosciences in the J. William Fulbright College of Arts and Sciences.