Nature Quest: The Earthquake Prediction Problem

Their whole life, producer Hannah Chinn https://www.npr.org/people/1255819925/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 https://www.npr.org/people/767284140/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 [email protected] mailto:[email protected]. Check out our previous episode on earthquake prediction https://www.npr.org/2021/07/22/1019335731/can-we-predict-earthquakes-hint-no. 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 http://plus.npr.org/shortwave. Listen to Short Wave on Spotify https://n.pr/3HOQKeK and Apple Podcasts https://n.pr/3WA9vqh. 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 https://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 https://www.npr.org/about-npr/179878450/privacy-policy

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

• 0:00Emily Kwong?

  This message comes from Planet Visionaries. Host Alex Honnold sits down this season with extraordinary doers, creating real climate solutions. Listen or watch wherever you get your podcasts. You're listening to Short Wave from NPR.

• 0:19Emily Kwong?

  Hey, Short Wavers. Emily Kwong here.

• 0:20Speaker 01

  And Hannah Chen.

• 0:21Emily Kwong?

  With this month's installment of Nature Quest.

• 0:24Speaker 01

  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-privileged TM to investigate a question that I've had for a while about earthquakes.

• 0:40Emily Kwong?

  OK, tell me more.

• 0:41Speaker 01

  So I'm from Portland, Oregon, and Portland is not a hotspot 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.

• 1:08Emily Kwong?

  The big one.

• 1:12Emily Kwong?

  This sounds kind of scary because I always picture, you know, Pacific Northwest is very like chill. This is the opposite of chill.

• 1:19Speaker 01

  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?

• 1:32Speaker 02

  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.

• 1:44Speaker 01

  Scientists say this earthquake, it'll demolish buildings, rupture utility lines, liquefy soil.

• 1:51Speaker 02

  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.

• 2:07Speaker 01

  But Emily, even though we know so much about how this earthquake could affect us, we still know very, very little about when it's going to happen. 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 seismologist at Oregon State University. He said they don't even use that word.

• 2:27Speaker 03

  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.

• 2:35Speaker 01

  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?

• 2:53Emily Kwong?

  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 Short Wave, the science podcast from NPR.

• 3:13Speaker 04

  Stay tuned for the following announcements and messages from our sponsors. This message comes from Edward Jones. Where they believe rich is more than caring about the latest and greatest. It's also about taking care of what gives your life meaning. That's why your dedicated financial advisor meets you where you are with personalized financial strategies that help protect what matters so you can preserve your progress while creating a path forward. The key to being rich is knowing what counts. Let's find your rich together. Edward Jones, member SIPC.

• 3:48Emily Kwong?

  This message comes from Planet Visionaries. If you're looking for a dose of optimism, Planet Visionaries is the podcast you need. Host Alex Honnold sits down this season with extraordinary doers creating real climate action. It's a lineup that proves hope isn't naive. It's fuel for change. In partnership with the Rolex Perpetual Planet Initiative, this is Planet Visionaries. Listen or watch wherever you get your podcasts.

• 4:13Speaker 04

  This message comes from Google Workspace with Gemini. One subscription that does it all. Personalized AI and premium business versions of Gmail, Google Docs, Drive, and more. Try it free for 14 days at g o o dot G L E slash Workspace with Gemini.

• 4:31Emily Kwong?

  Okay, Han, today we are talking about earthquakes and the difficulty 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?

• 4:44Speaker 01

  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 1,000-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, there's also more specific records that we have, human records from somewhere clear across the other side of the world, Japan.

• 5:10Emily Kwong?

  Oh, that makes sense because Japan is extremely earthquake-prone. It sits at like the confluence of multiple tectonic plates.

• 5:16Speaker 01

  Yeah, exactly. So when a big earthquake hits there, it's often followed by a tsunami wave. It goes like earthquake, tsunami, earthquake, tsunami. But in the year 1700, on January 26, 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.

• 5:39Speaker 03

  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 then they had written records of this.

• 5:51Speaker 01

  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.

• 6:07Speaker 03

  And so Kenji Sataki, a Japanese colleague, modeled the tsunami. You know, where did it come from? Did it come from Alaska, or Kamchatka, or Chile, or wherever? And the only place that matched was Cascadia.

• 6:19Speaker 01

  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 9:00 PM.

• 6:33Emily Kwong?

  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.

• 6:42Speaker 01

  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 9s, every 500 years on average.

• 6:59Emily Kwong?

  Oh, then we're fine, right? Because if the last big one was in 1700, that's way less than 500 years ago. So it's fine, right?

• 7:07Speaker 01

  So this is what I thought, too. But Diego told me it's not that simple.

• 7:11Speaker 02

  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 9s only 250 years apart, then maybe a 1,000-year period of calm, then a quick succession of other big earthquakes. So even though it's 500 years on average, it is not the case that they happen 500 years, nothing, earthquake. 500 years, nothing, earthquake. That's not how Earth works. I wish it were.

• 7:42Emily Kwong?

  But these tectonic plates are like, we don't follow rules. We don't observe patterns.

• 7:46Speaker 01

  Yeah. So we could be due for a major earthquake, or we could be fine for the next 500-plus years.

• 7:53Emily Kwong?

  Either or. OK.

• 7:54Speaker 01

  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.

• 8:03Speaker 03

  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 has it been going 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.

• 8:22Emily Kwong?

  That sounds like how I cook. Point is, earthquakes are like chaotic turkeys.

• 8:29Speaker 01

  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.

• 8:40Emily Kwong?

  OK.

• 8:41Speaker 01

  But here's what we do know.

• 8:42Speaker 02

  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.

• 8:50Emily Kwong?

  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.

• 9:02Speaker 01

  Yeah, and so that's the second part of the story. There's all of these things about earthquakes that science can and does predict, like what could happen when the big one hits.

• 9:11Emily Kwong?

  How do scientists figure that out? Just knowing like, if it's a X magnitude earthquake, it will do this?

• 9:17Speaker 01

  They look for clues from the past, and they can find those in places like estuaries and tidal marshes.

• 9:22Speaker 05

  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.

• 9:36Speaker 01

  So this is coastal geologist and paleoseismologist Tina Dura. She works in the geosciences department at Virginia Tech.

• 9:42Speaker 05

  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 past earthquakes.

• 10:01Speaker 01

  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.

• 10:10Emily Kwong?

  So it's like reading tree rings. It tells the story of the geology. What does looking at a record like that tell her?

• 10:17Speaker 01

  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 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 1 millimeter a year.

• 10:41Emily Kwong?

  Whoa.

• 10:41Speaker 05

  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 2 meters.

• 10:54Speaker 01

  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.

• 11:20Emily Kwong?

  So whole areas might stay flooded?

• 11:23Speaker 01

  Yeah.

• 11:24Emily Kwong?

  Wow.

• 11:25Speaker 01

  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 paleoseismologist we heard from earlier.

• 11:50Emily Kwong?

  Yeah, the one with the incredible turkey metaphor.

• 11:52Speaker 01

  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 earthquakes in one another.

• 12:27Emily Kwong?

  That sounds like a big, bad set of dominos, just 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?

• 12:44Speaker 01

  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.

• 12:53Speaker 02

  The idea is quite simple. We need seismometers, sensors that feel the first teeny tiny vibrations.

• 13:00Speaker 01

  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.

• 13:12Speaker 02

  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 5, they're not from a magnitude 6, they're probably from magnitude 8 or from a magnitude 9. 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.

• 13:43Speaker 01

  This entire early warning system can be activated in 15 to 20 seconds, totally automated without any human action.

• 13:49Emily Kwong?

  That's astonishing. I mean, 15, 20 seconds doesn't sound like a lot of time, but just even a little bit of advanced warning could be the difference between life and death, you know?

• 13:57Speaker 01

  Yeah, exactly. And all the scientists that I talked to, they told me it's really good to know everything that we can about how this big earthquake will play out, even if we don't know exactly when it'll play out.

• 14:09Speaker 02

  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 with that knowledge, I can develop goals and objectives.

• 14:25Speaker 01

  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 gonna 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 gonna take time, but Diego told me we're making progress. We have everything that we need to prepare.

• 15:02Emily Kwong?

  Hannah Chin, you have repped your region well to get ready for this. Thank you for bringing this to all of us.

• 15:10Speaker 01

  Thank you so much for having me.

• 15:13Emily Kwong?

  Shortavers, 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 [email protected]. We will listen and may even build an episode around your question.

• 15:28Speaker 01

  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.

• 15:36Emily Kwong?

  This episode was produced by Hannah and Rachel Carlson. It was edited by our showrunner, Rebecca Ramirez. Tyler Jones checked the facts, and Kwesi Lee was the audio engineer.

• 15:44Speaker 01

  Beth Donovan is our vice president of podcasting. And special thanks to Paul Lundgren and Suzanne Carbone, whose research and expertise helped inform this episode.

• 15:52Emily Kwong?

  I'm Emily Kwong.

• 15:53Speaker 01

  And I'm Hannah Shin.

• 15:54Emily Kwong?

  Come back for more Short Wave from NPR. See you later.

• 16:04Emily Kwong?

  Stay tuned for the following announcements and messages from our sponsors.