People and rescue workers work on the debris of a collapsed building in Caracas, after two strong earthquakes struck Venezuela.
Adilzon Gamez/Getty Images
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Adilzon Gamez/Getty Images
A major earthquake in Caracas – where older buildings are vulnerable to strong shaking – could have caused massive damage. A pair of them less than a minute apart were uniquely destructive, says geophysicist William Barnhart of 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 was almost three times more powerful.”
Barnhart says the fact that they attacked land close to major population centers made them especially deadly. “This is a terrible tragedy,” he says.
Barnhart says it’s too early to say what happened beneath the Earth, but it appears that both earthquakes may have occurred on two different faults. Many faults intersect each other in this tectonically complex region.
“There’s not just one easily identifiable fault that you can point to and say, ‘The earthquake definitely happened on this fault,'” says Barnhart.
Historically, when experts evaluated earthquake risk, they didn’t necessarily account for this multifault scenario, says paleoseismologist Chris Goldfinger of Oregon State University. “We always assume that an earthquake will happen on one fault and one fault only,” he says.
Goldfinger says that in 2016, a multifault event – the Kaikoura earthquake in New Zealand – took people by surprise, and changed scientists’ understanding of how interconnected faults can cause multiple ruptures. Assuming Venezuelan earthquakes are similar, he says, this would be important information for those who study such risks.
“The first one was completely unexpected. We had no idea this could happen,” says Goldfinger. “And here’s another earthquake 10 years later where we had two very large earthquakes on different faults.”
There are other locations around the world with multiple faults. Parts of California’s fault system, including the San Andreas Fault, have equally complex tectonics.
A recent study found that parts of the San Andreas and San Jacinto fault systems may now be at their highest modeled stress levels in at least 1,000 years. This is what experts say The California region is far more prepared for such an event than Venezuela.
Goldfinger says that level of preparation is rare. In many places, engineering has not kept pace with rapidly evolving seismology.
“Many of these buildings around the world were built before plate tectonics,” he says. “But it’s an intimidatingly daunting thing to think about remodeling an entire city.”
The Venezuela earthquake was accompanied by two other earthquakes, one in Japan and the other in California. “As we understand things, all these earthquakes are completely unrelated,” says Barnhart, a USGS geophysicist.
He noted that although the Venezuela earthquakes were unusual in many ways, their coincidence with two other, unrelated earthquakes on the same day was not as remarkable as it might seem.
“Earthquakes happen all the time,” says Barnhart. “Most people don’t pay attention because most earthquakes happen in the ocean and no one is affected.”
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