Short Wave - Nature Quest: The Earthquake Prediction Problem

Episode Date: November 25, 2025

Their whole life, producer Hannah Chinn has known about the Big One: a massive earthquake forecasted to hit the West Coast. Scientists say it’ll destroy buildings, collapse bridges, flood coastal towns and permanently shift the landscape. But how exactly do scientists know this much about the scope of earthquakes if they can’t even predict when those earthquakes are going to happen? Together with host Emily Kwong, Hannah goes on a quest for answers. Plus, they get into what a Cascadia earthquake has in common with a Thanksgiving turkey.This story is part of Nature Quest, our monthly segment that brings you a question from a Short Waver who is noticing a change in the world around them. Have an environment-based question you want us to investigate on the next Nature Quest? Email us your question at [e-mail] out our previous episode on earthquake prediction.Listen to every episode of Short Wave sponsor-free and support our work at NPR by signing up for Short Wave+ at plus.npr.org/shortwave.Listen to Short Wave on Spotify and Apple Podcasts.This episode was produced by Hannah Chinn and Rachel Carlson. It was edited by Rebecca Ramirez. Tyler Jones checked the facts. The audio engineer was Kwesi Lee. Special thanks to scientists Paul Lundgren and Suzanne Carbotte.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

You're listening to Shortwave from NPR. Hey, shortwavers, Emily Kwong here and Hannah Chin with this month's installment of Nature Quest. And Emily, full disclosure, I'm doing something a little bit selfish today. Instead of answering a real listener question, I'm using my producer privilege TM to investigate a question that I've had for a while about earthquakes. Okay, tell me more. So I'm from Portland, Oregon. And Portland is not a hot spot for earthquakes. We just don't experience them multiple times a year, you know, the way Californians do.

But Portland is right next to the Cascadia Subduction Zone, which is this underwater fault line in the Pacific Ocean that stretches from Canada all the way down to Northern California. And as long as I can remember, Portlanders have known that an earthquake is coming. When we talk about it, we call it the big one. This sounds kind of scary because I always picture, you know, Pacific and a earthquake. Northwest is very, like, chill. This is the opposite of chill. It is the opposite of chill. So I called up a seismologist.

His name's Diego Melgar, and he's the director of Crescent, the Cascadia region, Earthquake Science Center. And I asked him, like, what would an earthquake this big feel like? You would feel shaking where it's difficult, maybe even impossible for you to stay standing, for anywhere between one or three minutes. Start counting right now and realize how long that is. Scientists say this earthquake, it'll demolish buildings, rupture utility lines, liquefy soil. We might get significant collapses of bridges and any old infrastructure. We would get thousands of landslides across the region, most of them covering major thoroughfares, especially in places that are very steep, like the coast ranges. But, Emily, even though we know so much about how this earthquake could affect us, we still know very, very little about.

about when it's going to happen. We don't know when? We can't predict it at all. One scientist I talked to, his name is Chris Goldfinger, and he's a marine geologist and paleo-sysmologists at Oregon State University. He said they don't even use that word. Prediction is sort of in the science world,

as we call it the P-word. We just don't really even speak about it because nobody can do it. The P-word. We don't do that in earthquake science. And listening to this, Emily, I was like, why is that? Right?

Why do we know so many concrete details about certain parts of this looming disaster? And then zero details about this other seemingly really crucial part of when is it going to happen? Today on the show, the earthquake prediction, problem, what we know and what we don't about quakes like the big one, and how the science is shifting under researchers feet. You're listening to Shortwave, the science podcast from NPR. Okay, Hand, today we are talking about earthquakes and the difficult to, of predicting them, which is kind of scary when it comes to the magnitude 8, the magnitude 9 ones, the big ones. But how do you know a big one is coming for the Pacific Northwest?

That's a great question. So first, there's geologic clues of past earthquakes in the landscape. There's what we call ghost forests, these thousand-year-old trees on the Oregon and Washington coast that seem to have been submerged in seawater really quickly. And then in other places, you can find sand deposits in the soil that must have come from big earthquakes. And second, And there's also more specific records that we have. Human records from somewhere clear across the other side of the world, Japan. Oh, that makes sense because Japan is extremely earthquake prone. It sits at like the confluence of multiple tectonic plates.

Yeah, exactly. So when a big earthquake hits there, it's often followed by a tsunami wave. It goes like earthquake, tsunami. But in the year 1700 on January 26th, Japanese scholars have all of these records of what they call the quote unquote orphan tsunami. Orphan, because they didn't know where it came from. It just didn't seem to have a parent earthquake preceding it. And this tsunami arrived out of nowhere with no earthquake to go with it, no warning. It killed a few people, destroyed some boats, and destroyed bales of rice in warehouses.

And they had written records of this. So this is Chris again, the seismologist. He says the Japanese records were really accurate, down to the height of the flooding and the amount of the destruction. And using these records, it was possible for scientists to do. some detective work and figure out where that big wave came from. And so Kenji Sataki, a Japanese colleague, modeled the tsunami. You know, where did it come from? Did it come from Alaska or Kamchaca or Chile or whatever? And the only place that matched was Cascadia.

Which, Emily, again, is that fault line right off the Portland coast. So that research is how we know that the last great earthquake in the Pacific Northwest was January 26th, the year 1700, about 9 p.m. That is so precise. It's incredible, actually, that they were able to track the last, you know, big one in the region to that moment in time, 325 years ago. No, it's really cool. And scientists have done more modeling. They've researched earthquakes in the area further and further back. They've talked to indigenous people who have told stories about these quakes for generations. And they've realized that Cascadia has these really big earthquakes, usually magnitude nines, every 500 years on average. Oh, then we're fine, right? Because if the last big one was in the same. 1700, that's way less than 500 years ago, so it's fine, right? So this is what I thought too, but Diego told me it's not that simple.

Earthquakes can cluster in time. So it can be that every now and then the earthquakes happen in quick succession. So we could have a few magnitude nines only 250 years apart, then maybe a thousand year period of calm, than a quick succession of other big earthquakes. So even though it's 500 years on average, it is not the case that they have. happen. 500 years, nothing, earthquake. 500 years, nothing earthquake. That's not how Earth works. I wish it was. These tectonic plates are like, we don't follow rules. We don't, we don't observe patterns. Yeah. So we could be due for a major earthquake, or we could be fine

for the next 500 plus years. Either are. Okay. Our other seismologist, Chris, he compared it to figuring out when your Thanksgiving turkey is ready if all you did was stick it in the oven and walk away. somebody says, is it almost done? Well, I don't know. When did you turn it on? I don't remember. And you see the oven sitting there at 350 and you go, well, how long's it been gone at 350? I have no idea. And you don't have a turkey thermometer either. So you have no way of measuring when the cycle started or how far into it you are or how cooked it is. That sounds like how I cook. Point is earthquakes are like chaotic turkeys. Right. And just to complicate this a little further, Emily, because I know that's what you're dying to hear. We don't even know for sure that this will be a magnitude 9 earthquake.

It could be a little bit smaller, catastrophic, but not quite that big. Okay. But here's what we do know. We have really good idea of what the tsunamis are going to look like and what the shaking is going to look like. And that's actionable information that we put to use. That's important because since earthquakes can cause tsunamis, knowing what different size earthquakes will do to the land, to the water is really important for human health and safety. Yeah, and so that's the second part of this story. There's all of these things about earthquakes that science can and does predict,

like what could happen when the big one hits. How do scientists figure that out, just knowing, like, if it's an X magnitude earthquake, it will do this? They look for clues from the past, and they can find those in places like estuaries and tidal marshes. So when we have a big Cascadia earthquake, tsunami washes in sand and deposits it on these marshes, and that sand is then preserved in the stratigraphic record, so in the coastal sediments over time. So this is coastal geologist and paleo-sizmologist Tina Dura. She works in the geosciences department at Virginia Tech. We actually go out there with a tube and push it down into the ground.

And, you know, the oldest earthquakes are at the bottom of the record. And as you go up towards the surface and the sediments, you see the younger earthquakes. And in some of these marshes, we have up to a 7,000-year record of. of past earthquakes. Tina showed me a picture of one of these sediment core samples. It kind of looks like a layer cake. You can see the marsh dirt and then the tidal dirt on top of it and then the tsunami dirt and then it goes all over again. So it's like reading tree rings.

It tells the story of the geology. What is looking at a record like that tell her? She told me that between earthquakes, basically when there's pressure building up on these tectonic plates, it causes the land to rise, which, for what it's worth, is part of the reason that climate-driven sea level rise hasn't really. really affected the coastlines of the Pacific Northwest, the way it has, say, the Gulf of Mexico, et cetera, because the land is rising along with the ocean. It's rising at about one millimeter a year. Whoa. But of course, the next earthquake is going to reverse that. And this land level change, where it goes down, is going to happen over minutes. And it's going to cause a sudden sea level rise

of up to two meters. Combined with the already existing tsunami waves that were predicted to have, you'd get flooding, a lot of flooding, mostly in low-lying areas along the coast, the places that are flat and easy to build on where there are already airports and fire stations and wastewater treatment plants. And unlike other tsunamis, where the flooding comes in and then goes away, Tina said the combination of the land drop and the waves is going to mean a much more permanent change to the landscape. So whole areas might stay flooded? Yeah. Wow. And the other thing that's important to know, Emily, is that this might not just affect the upper half of the West Coast. It could also trigger another earthquake further south, the California big one.

So just south of the Cascadia fault is this other tectonic plate boundary called the San Andreas fault. And that one's responsible for a lot of earthquakes in California. Remember Chris Goldfinger? He's the paleo-sysmologist we heard from earlier. Yeah, the one with the incredible turkey metaphor. Absolutely. So in 1999, through a clerical, error, he and his research team ended up sailing too far south and taking a sample of the San Andreas fault. And as they were comparing these samples, one from the Cascadia fault and one from the San Andreas fault, they realized that all the events that these cores recorded were happening super close together, just time-wise, which is super weird, right? So they took way more samples,

they got way more data, and they realized that the Cascadia and the San Andreas were what geologists call seismically linked. They have the potential to trigger Earthquist's in one another. That sounds like a big, bad set of dominoes just like tipping down the West Coast. Okay, so more flooding, more landscape change, bonus earthquakes. Is there anything else we should know about the big one? Like, is it just going to be, or are we just powerless in the face of it? We are not. There's good news.

Because in the past few decades, scientists have developed the technology to create an earthquake early warning system. The idea is quite simple. We need seismometers. sensors that feel the first teeny tiny vibrations. Diego told me we have thousands of these little sensors located all throughout Washington and Oregon and California, and they're all just listening to the earth,

waiting to hear these tiny, tiny vibrations. And using decades of research and models, we know that if the teeny tiny vibrations look a certain way, then these teeny tiny vibrations are not from a five. They're not from a magnitude six. They're probably from magnitude eight or from a magnitude nine. And after a few of these seismic stations detect these teeny tiny vibrations, then all the logic algorithms and technology kicks in. And the alert goes off by cell phones, by emergency, sirens, and so on.

And it says, you know, earthquake, drop cover and hold on. This entire early warning system can be activated in 15 to 20 seconds, totally automated without any human action. That's astonishing. I mean, 15, 20 seconds doesn't sound like a lot of time, but just even a little bit of advance warning. Could be the difference between life and death, you know? Yeah, exactly. And all the scientists that I talked to, they told me it's really good to know everything we can about how this big earthquake will play out. Even if we don't know exactly when it'll play out.

This is the point in the conversation at which I tell people, knowledge is power. And I'd rather know that these are the challenges we're facing. That the tsunami is probably going to be this size. That the shaking is probably going to be this intense. Because aren't with that knowledge, I can develop goals and objectives. And Diego says that's the next step, right? If you're in the Pacific Northwest, and especially if you're in a coastal town, make sure you have those goals and objectives.

Make sure you have a flooding plan. Ask your neighbors if they have one. Because when this happens, it's likely that medical experts won't be able to reach everyone. So we're going to need to rely on other people in our communities. Find out whether your state agencies and local emergency managers have an earthquake plan or write a letter to your legislators and ask them to push for earthquake-proof buildings and evacuation centers. It's going to take time.

But Diego told me we're making progress. We have everything that we need to prepare. Hannah Chin, you have repped your region well to get ready for this. Thank you for bringing this to all of us. Thank you so much for having me. Trojivers, if you have a question about your local environment, open up your phone and record us a little voice memo about it, you know, your feelings, your thoughts, your observations,

and then email that voice memo to shortwave at npr.org. We will listen and may even build an episode around your question. Also, if you want to learn more about earthquake science and seismometers, you should check out another episode we did a while ago. We'll link to it in the show notes. This episode was produced by Hannah and Rachel Carlson. It was edited by our showowner, Rebecca Ramirez. Tyler Jones checked the facts, and Clacy Lee was the audio engineer.

Beth Donovan is our vice president of podcasting, and special thanks to Paul Lundgren and Suzanne Carbott, whose research and expertise helped inform this episode. I'm Emily Kwong and I'm Hanishin. Come back for more shortwave from NPR. See you later.