Poor building codes, perfect-storm earthquake led to massive destruction in Haiti, experts say
The catastrophic earthquake in Haiti was in many ways a perfect storm: A strong, shallow temblor beneath a densely populated area with few building codes.
The magnitude 7.0 quake occurred along the boundary separating two major tectonic plates, the Caribbean and North American plates.
Most of the movement along these plates is what is known as left-lateral strike slip motion, according to the U.S. Geological Survey, with the Caribbean plate moving eastward in relation to the North American plate.
Kate Hutton, a seismologist at Caltech, said that the severity of the Tuesday's quake was due to three major factors: the size of the quake itself, the fact that it struck under an urban center with a high density, and that it happened in a region with few building codes or enforcement.
In many ways, said Hutton, the quake was similar to quakes seen along the San Andreas fault: It was shallow, a fact that enhances the intensity and makes it more localized to the region right along the fault.
"We are not surprised by any of it," Hutton said.
Hutton said that the Haiti quake was almost the same size as the 1989 Loma Prieta quake in Northern California. That quake, she said, "caused a lot of damage, but it wasn't a disaster like this in terms of the number of people injured and killed."
Early indications, according to the USGS, are that the main quake Tuesday was a left-lateral strike slip along the Enriquillo-Plantain Garden fault system. That system has not produced a major earthquake in decades, if not longer.
Tim Dixon, a professor of marine geology and geophysics at the University of Miami, studied the island of Hispaniola, which includes Haiti and the Dominican Republic, in the late 1990s. He said that scientists had believed that the fault zone along the island's south coast was inactive, and that it was the north coast that was more earthquake-prone.
But he said that by looking at historical records, kept by Jesuit priests working in the area, and making modern measurements, they were able to conclude that "the south coast of Hispaniola was active, and earthquake-prone."
The reason, he said, is that the boundary between the two plates is much more complex than scientists first thought.
--Cara Mia DiMassa in Pasadena
Map credit: U.S. Geological Survey