Scientific Analysis of the Earthquake Sequence

Today on State of the World, earthquakes cause devastation in Venezuela . You're listening to State of the World from NPR. We bring you the day's most vitalnational st Interories up close where they're happening. It's Thursday, june twenty fifth. I'm Greg Dickson. What appear to be back to back earthquakes hit Venezuela on Wednesday, with a death toll that's likely to be in the hundreds at least. A state of emergency has been declared in a nation that was politically and economically fragile before this natural disaster hit. Rescue workers are searching buildings for survivors as help begins to arrive from nearby countries . In a few minutes, how unusual is it for two earthquakes to hit back to back? We'll hear from scientists. First, reporter Manuel Rueda is in neighboring Colombia. He's been talking to people in Venezuel a to get a better sense of what's happening. After the earthquake struck, firefighters and volunteers worked to clear debris from the Petunia, a thirteen story apartment building in Caragas that collapsed. More than a dozen people were rescued from the building according to local officials, but many are still thought to be trapped there. Sebastian Aarius showed up with a shovel and the sledge hammer to see if he could help. Rescue workers are so short of equipment they've been asking volunteers to show up with their own tools. In a place like this, you just feel shocked, he said. I don't even feel like taking photos. By the time Arius got to the Petunia building there were too many volunteers on site, so he set out to other neighborhoods where there were also reports of collapsed buildings. Maybe they need more tools there , he said. Earthquakes are relatively rare in Venezuela, and residents of Caracas seldom feel even minor tremors. The quakes hit hardest in Caracas and five northern states along Venezuela's Caribbean coast . Claudia Castillo says she was working at home on her computer when the first earthquake struck. Everything was moving, she says. My flower vases were cr ashing on the floor and even paintings were falling off the walls. I had never experienced something like this. Anna Sofed lives in Los Palos Grandes, a neighborhood in Caracas where at least three buildings have collapsed. She was driving past the shopping mall when the first earthquake struck and I saw people running out a shopping mall. I saw a big smoke of sand. I decided to breathe , to do breath exercises because all my body was shaking. In La Guida, city along Venezuela's Caribbean coast, dozens of buildings have collapsed according to officials. Videos shared by local journalists show people trapped inside concrete structures , screaming out their names as they wait for help. As rescue crews searched for survivors , neighboring countries began mobilizing aid. U. S. Secretary of State Marcarubio says rescue teams from Virginia and California are also underway. We're also helping them with some overhead imagery, especially in coastal areas where they don't have full visibility over what the damage has been or what the impact has been. The response to these earthquakes is expected to test relations between Venezuela and the Trump administration, which seized former Venezuelan leader Nicolas Maduro in January in a pre dawn raid . Acting President Delsi Rodriguez has thanked the Trump administration for its quick response. In a nationally televised address, she declared a state of emergency. We need all doctors and nurses to report to their places of work, she said. Venezuela's main airport has been closed after its ceiling was damaged, and schools will be shut down for the remainder of the week. Rodriguez urged residents to evacuate buildings that remain standing and are no longer safe because of structural damages to their foundations. Please stay calm, she said. We need to stay united. The last time Karakas experienced such an intense earthquake was in nineteen sixty seven when more than two hundred people were killed in a six point seven magnitude quake Thousands are now sleeping outdoors fearful of more aftershocks . For them, the recovery has only just begun for NPR news, I'm Manuel Dere in Boroda . As scientists sort through the data from this event , they say this earthquake sequence appears to have some unusual features. NPR's Katie Riddle tells us more . In Caracas, many older buildings are vulnerable to strong shaking. One major earthquake could have caused widespread damage. A pair of them proved catastrophic. William Barnhardt is a geophysicist at the U. S. Geological Survey in Golden, Colorado. A magnitude seven point two earthquake alone in this region would be a devastating earthquake , but it was followed thirty nine seconds later by a magnitude seven point five earthquake that's about three times more powerful. The fact that they struck on landose. to C mlajor popul ation centers, says Barnhart made them especially deadly. It's just an awful tragedy. Barnhart says it's too early to say conclusively exactly what happened under the earth. It appears these two quakes may have occurred on two separate faults. That's because of the unique geology underpinning the region. Several faults intersect. There's not just a single easily identifiable fault that you can point to and say the earthquake definitely happened on this fault. Historically, when experts evaluate earthquake risk, they haven't necessarily accounted for this multifault scenario, says Chris Goldfinger. He's a paleo seismologist at Oregon State University. We always tend to kind of assume that earthquakes will just be on one fault and only on one fault. Ten years ago, a multi fault event like this in New Zealand took people by surprise, says Goldfinker. If this one turns out to be similar, he says, It will be important information for those who study this kind of risk. And the first one was completely out of the blue. We had no idea that could happen at all. And here's a second one ten years later, where two really big earthquakes happened on separate faults. Parts of California's fault system, including the San Andreas, have similarly complex tectonics. Experts say that area is far more prepared than caracas, but Goldfinger says that's rare. Many of these buildings around the world were built before Plate Tectonics . So it's just an intimidatingly difficult thing to think about retrofitting entire cities. Hopefully, he says, experts like him and his colleagues can learn from this unusual event so that the next one might not be quite as tragic. Katie Riddle in Pyrrhenews That's the State of the World from NPR . Thanks for listening.