Since 1989, Eric Calais, Andrew Freed and a host of additional earth sciences colleagues have been studying the complex network of geological plates pushing each other throughout Hispaniola; the island that hosts the countries of the Dominican Republic and Haiti. After nearly 20 years of watching pressures build and tensions mount, the team announced that the Enriquillo and Septentrional faults were ripe for a major earthquake.
You all know what happened. Less than two years later, the fault shifted, resulting in a 7.0 earthquake that killed more than 200,000 people and causing an estimated $8 billion in damages, roughly 100 percent of the country’s Gross Domestic Product.
In a new paper recently published in Nature Geosciences, the two co-authors from Purdue University report that the earthquake actually was caused by a previously unknown fault, which they have named the Léogâne fault. The Léogâne fault runs parallel to the Enriquillo fault, but further underground, slanting further downwards the further north it runs. But unike the Enriquillo fault, it is a blind thrust, meaning one side of the fault is being thrust over the other between the Caribbean and North American plates.
The team used GPS devices radar interferometry to measure how the terrain shaked, rattled and rolled during the earthquake. The technology can tell them what’s going on beneath the surface as far as 20 kilometers below the surface. The team then used a computer model to determine what characteristics the source of the earthquake would have to have had in order to produce the changes.
But before they even got around to analyzing the results, they had a feeling something was fishing. There was no rupture on the surface; a feature they expected to see from any earthquake emanating from the Enriquillo fault, which lies very close to the surface. And sure enough, after the data rolled in, they found that the epicenter area rose by a little more than half a meter and that the earthquake caused contraction of the Earth’s crust opposite of what would be expected from the Enriquillo fault.
What this means for the people of Port-au-Prince is not certain. When earthquakes go off, it can cause nearby faults to either gain energy or release it. And it’s nearly impossible to predict which without lots and lots more studying.
So, theoretically, the city could be poised for a second strike just as devastating as the first.
Of course it is impossible to predict this, especially so quickly. But locals should make sure that as they begin to rebuild, they do so with earthquakes in mind. Making structures capable of handling the disaster would save a lot of lives, and a lot of money, in the future.