Short Wave - Inside Colombia's big quake – and why more could be coming

Episode Date: August 14, 2026

The 7.4 magnitude earthquake that struck Columbia was devastating. Host Regina Barber talks to earthquake geologist Rodrigo Alejandro Leon Loya about the tectonic plates that caused the quake and what it was like 150 miles from the epicenter. Interested in more science in the news? Email us your question at [e-mail].   Support public media with NPR+ and enjoy perks for over 25 podcasts like this one. This show’s perks include sponsor-free listening. Learn more at plus.npr.org. See pcm.adswizz.com for information about our collection and use of personal data for sponsorship and to manage your podcast sponsorship preferences.NPR Privacy Policy

Hey, Shortwavers. It's Regina Barber with a quick ask to follow the show on the NPR app or whichever app you're hearing us from. On Apple, it's a plus sign. You won't miss an episode from us and we'll grow our community. Okay, here's the show. You're listening to Shortwave from NPR. Rodrigo Alejandra Leon Loya is used to earthquakes, but not ones like this. This one just starts with a very huge amount of business. It was very long because of the magnitude. We could feel around a minute and a half of shaking. He's talking about the 7.4 magnitude earthquake that struck Western Columbia on August 10th. The quake left collapsed buildings and destruction in its path and killed hundreds of people.

But Rodrigo doesn't live in Western Columbia. He lives in Bogota, which is about 150 miles east of the quake's epicenter. And as an earthquake geologist at the University of Los Andes in Bogota, he says right when the earthquake hit, he wasn't scared. He was more curious. In the moment, I want to know what happened or what we happen. More like a state of alert, like, okay, this is huge. Where they will happen, what would be the damages. I run to the computer to start to see signals and the,

and the report. And after a big shake like that, a natural question might be, when will the next one happen? And can we predict it? Unfortunately, in seismology, prediction is tough to do. The word prediction, it's a huge word

that is not in the science community, but forecast is a really good compromise. So we can forecast the number of earthquakes and the range of magnitude each year. Rodrigo says the scientists predict there will be 17 to 19 earthquakes above a magnitude 7 in any given year worldwide. In the forecast, I guess there's room for 6 or 7 more earthquakes above 7.

And potentially one above an 8. This year, actually, we haven't had the big one. Today on the show, the Colombian earthquake. And why the depth of an earthquake? makes a big difference in the aftermath. Plus, if scientists can predict them, what can we do to safeguard people in the future? Okay, Rodrigo, take us beneath the surface.

Like, what is physically happening when an earthquake like this, the one that happened in Colombia? When it starts, what plates under the surface are causing the ground to suddenly move? We need to imagine that the NASCA plate is going, down into the mantle. When it reaches about 100 kilometers, the pressure is very, very high.

And the slab can host a brittle rupture, an earthquake. So these are not really frequent, but they are not strange for the seismological community. The depth of the earthquake has implicated. because the deeper you go, the more attenuated the seismic waves will have. This means that it was a big earthquake, but it was the best scenario that Colombia could have

in the light of the damage that we are seeing. Because it could have been even higher up in the mantle and closer to the surface, and that would have been more damaging. Yeah, like a Venezuelan-style airquick. for example. So because, like, Columbia sits in this, like, specific region, it's, like, more susceptible to earthquakes. Can you tell me about these different tectonic plates that are involved in this region?

Yeah. There are three big plates that are interacting. That is the NASCA plate. That is an oceanic crust, oceanic plate. that is traveling from the Pacific Ocean and it's smashing into the continent. And the continent is the South American plate. To the north, you have the Caribbean plate that is not colliding,

but rather sliding through. Oh, it's sliding. Oh, wow. Okay. Yeah, like the San Andreas fault system, for example, you have the Pacific and the North American plate sliding each other. Okay. But between these three big plates, there is a microplate that is called the Nord-Andian block.

And these three plates impose a huge amount of stress into the North Andian block. And this stress is expressed in fault systems that are hosted in the crust. So in Columbia, you can, for this tectonic setting, you can have shallow earthquakes that, will be hosted in crustal folds. You can have the megatrust earthquakes that are related to the convergence boundary between NASCAR and South America. And then you have deep earthquakes like the Monday earthquake that is hosted in the slab that is going beneath the South American plate.

So when you have all of these three plates, right, like does it make it so that it's more active? Like, is there going to be more earthquakes there? Yeah, we have a huge amount of earthquakes. And because of this complexity, we have many seismogenic sources. In other places, you just have to worry about the plate-border earthquakes. But in Colombia, there is at least three different seismogenic types of earthquakes. What's the difference between the earthquake that happened in Venezuela versus the one that just happened in Colombia?

Yeah, the main difference is that the Venezuelan earthquake was a really shallow earthquake. Which is one reason why that earthquake was so much more deadly, right? Yeah. Also, the earthquake in Venezuela is very complex because we call it like a multi-rruption event. A multi-rpture event. Okay. This means that more than one fault was activated during the earthquake. Oh. And actually there's an ongoing debate about, from a seismology point of view, you can say that there were two earthquakes, and separated by 40 seconds. Oh, wow.

But from a geology earthquake point of view, I say it was just one event. just the rupture process was delayed some seconds and then jumped to another segment. So what are the different kinds of earthquakes? So we talked about the subduction one where like one plate is going under another. And then we've talked about the fault one where the earthquake is created because those faults are like kind of sliding against each other. What are other kinds? Well, the Monday earthquake was, it's classified as an half-depth earthquake. Actually, there are deeper earthquakes.

For example, just going south in the Peru region, you had earthquakes that happen at 500 kilometers depth. Oh, wow. So they are very, very, very, very deep. You can imagine the subduction system, and you have the megatrossed earthquakes in the surface, the intermetic seismicity like the Monday earthquake, and then you have very, very deep earthquakes at 500. In general, when one earthquake happens, like what controls whether they'll be more that day, that week? Huge question. We can say that the shallower, you can have aftershock sequence with more events.

The deeper you go, the thermal structure of the slab, inhibits the aftershock sequence. Okay. You always, always, you will have after strikes. The difference is how many, how many and for how long? The bigger the earthquake, the longer the sequence will last. Because scientists can't predict the earthquakes, like, what does this mean for public safety if we can't predict? How do we help people? One part is making good hazard maps, comprehensive hazard maps, that can help the engineers to design good houses, good buildings.

The other part is designing early warning systems, but there is a very complicated task. For example, you can think of Mexico City. It's very far from the subduction zone. So you have at least half a minute between the arrivals of the seismic waves to the Mexico City. Wow. Okay, okay. Half a minute warning. So the guarding system can help the people to evacuate the buildings. Yeah.

But you think about L.A., for example. L.A. is on the top of the faults. Mm-hmm. So you won't have that time. Wow. So it depends in where part of the planet you are that you can design the early warning systems. So because where the city is and then also how many seismic detectors you have and like your system. What would you, what advice would you give to people that live in these areas that are just very prone because they're next to the faults or they're next to like three plates like you said,

these zones? What would be your advice? Being aware that things can get messy really fast and when the earth starts to move, you need to hold on, keep calm and wait to the shaking past because many people think that when the earth is moving, that they can just get up and get out of the building. And we saw the videos on Monday that people tried to run, and they just felt. So, yeah, keep calm. It's very easy to say, hard to do.

Rodrigo, thank you so much for talking with us today about earthquakes. And I'm glad you are safe after you experienced that earthquake yourself. Well, thank you very much for the invitation. As a seismologist, it's always a mixture of feelings speaking about this because I like the phenomena, but I do like the repercussions it has in the societies. This episode was produced by Juan Diego Ramirez. It was edited by Burley McCoy and Tyler Jones checked the facts. The audio engineer was Jimmy Keely.

I'm Regina Barber. Thank you so much for listening to Shortwave from NPR. here.