University of Miami geologists have analyzed images based on Synthetic Aperture Radar (SAR) observations taken before and after Haiti's devastating  January 12 earthquake. The images reveal surprising new details that may help the island better mitigate future earthquakes.

According to the new data, the earthquake rupture did not reach the surface--unusual for an earthquake this size. More importantly, the images confirm that only the western half of the fault segment that last ruptured in 1751 actually ruptured in the current earthquake.

"We're still waiting for the other shoe to drop," said Tim Dixon, professor of geology and geophysics at the University of Miami Rosenstiel School of Marine&Atmospheric Science.

The images reveal other startling facts, "Given the plate tectonic setting scientists expected mainly sideways motion, yet there was a large amount of vertical motion during the earthquake," said Falk Amelung, professor of geology and geophysics at RSMAS. "This explains how such a relatively small rupture was able to generate such a large earthquake."


(Photo Credit: Group on Earth Observations, JAXA, UM Rosenstiel School)

The data shows the earthquake occurred on or near the Enriquillo Fault, where most scientists suspected but until now did not have enough evidence to prove it. "This is a relief, because it shows that our current ideas about the tectonics of the area are correct," Amelung added.

The researchers are looking at every bit of evidence to try to understand the possibility of another major quake hitting Port au Prince in the near future. "There's a reasonable probability of another large quake, similar to the January 12 event, striking Port au Prince within the next 20 to 30 years," Dixon said. "I'd like to see them relocate critical infrastructure such as government buildings, schools and hospitals, farther north out of the danger zone."

In 1986, at the dawn of the GPS age, scientists began a set of geodetic measurements on the island of Hispaniola. A decade later, those measurements would reveal that the Enriquillo fault in southern Haiti was a significant earthquake hazard. "In a very real sense, those early measurements set the stage for our current understanding of this dangerous fault zone. Scientists have been studying this fault and others on the island, ever since," Dixon said.