What made the deadly Venezuelan earthquakes different

People and rescuers work on the debris of a collapsed building in Caracas after a pair of strong earthquakes struck Venezuela. Edilzon Gamez/Getty Images hide caption toggle caption Edilzon Gamez/Getty Images One major earthquake striking Caracas — where older buildings are vulnerable to strong shaking — could have caused widespread damage. A pair of them less than a minute apart was uniquely catastrophic, says William Barnhart, a geophysicist at the U.S. Geological Survey in Golden, Colo. "A magnitude 7.2 earthquake alone in this region would be devastating," says Barnhart. "But it was followed 39 seconds later by a magnitude 7.5 earthquake that's about three times more powerful." The fact that they struck on land, close to major population centers, says Barnhart, made them especially deadly. "It's just an awful tragedy," he says. Barnhart says it's too early to say exactly what happened under the earth, but it appears these two quakes may have occurred on two separate faults. Several faults intersect in this tectonically complex region. "There's not just a single easily identifiable fault that you can point to and say, 'The earthquake definitely happened on this fault,'" says Barnhart. Historically, when experts evaluate earthquake risk, they haven't necessarily accounted for this multifault scenario, says Chris Goldfinger , a paleoseismologist at Oregon State University. …