When the Earth moves, S11E2

s11 e2


What happens to bridges, buildings, and pipelines when the soil holding them up behaves like a liquid? Ben Mason, associate professor geotechnical engineering, has traveled the world doing post-earthquake reconnaissance to find out and make us better prepared for impending earthquakes.

Season number
Season 11
Episode number

[MOVIE CLIP: “San Andreas.” Warner Bros. Pictures, 2015.]

RAY GAINES: I’m gonna get you out. Run! Come on. Come here. Are you hurt? Are you hurt?
DR. LAWRENCE HAYES: People need to know that the shaking is not over. We’ll get hit again. And it’s going to be a bigger monster.

ROBERTSON: Humans seem to have a simultaneous fascination with and disbelief in disasters. There are movies about pandemics, fires, animal attacks, and, in the clip you just heard — earthquakes. In the movie “San Andreas,” an earthquake devastates Los Angeles and San Francisco. I like how the seismologist refers to the earthquake as a monster. Because a monster is something we are afraid of, but we also don’t truly believe in. Most of us don’t monster-proof our houses. And it’s hard to know sometimes what are the real monsters that we need to be preparing for, and what are the unrealistic fantasies. 

In this season of the podcast we are looking at how engineering can help prepare us for natural disasters. As you might have guessed, today our topic is earthquakes, and I’m your host, Rachel Roberson.

[MUSIC: “The Ether Bunny,” by Eyes Closed Audio, licensed under CC by 3.0.]

ROBERTSON: From the College of Engineering at Oregon State University, this is Engineering Out Loud.

ROBERTSON: Today we’ll hear from Ben Mason, associate professor of civil and construction engineering, who faces the earthquake monster in his daily work. He has traveled the world doing post-earthquake reconnaissance. I talked to him recently on my sunporch, where we are recording our podcast interviews in the open air. So, you might hear the occasional bird in the background.  He told me about his first reconnaissance trip — in 2011 after a 9.0 magnitude earthquake in Japan — when the devastating impact of earthquakes became painfully real to him.

MASON: We went up to the Sendai Plain in Northeast Japan, and that's where the tsunami came on shore, maybe with the most vigor. And we saw an entire village just washed away to its foundations. And the government had come in and basically stacked up all the debris in these large mounds. And so you see these mounds are probably like five, six stories, high of just debris. And you see these hobby horses and, like, soccer balls that the, the components of people's lives that are, uh, just sitting there, you know, and, and that was heavy. And I, you know, I actually vomited because it was so heavy for me. And I think that was, that was also, um, a turning moment for me and realizing like, OK, this is a, this is a very human endeavor. Our job here is to focus on, on the science, of course, but you can't decouple the science that you're doing from the human component. 

[MUSIC: “In My Head” by Poddington Bear, soundofpicture.com.]

ROBERTSON: The human component is particularly relevant for those of us living in Oregon, where scientists are predicting a 9.0 magnitude earthquake caused by the Cascadia subduction zone. And we’ll get back to the human component, but first let’s talk about the science.

MASON: In general, during earthquake shaking, one thing that can happen if you have, in particular, sandy soils that are fully saturated with water, is during the earthquake shaking, those sandy soils can lose all of their strength, lose all of their ability, to say, hold up a structure — a bridge. And they start behaving like a fluid or like a liquid. And that's why we call that, that process liquefaction. 

So, we went to places where we knew liquefaction was happening, and then we performed these geophysical techniques. And that, again, the point of that is to bring those back and then allow our community to improve our current understanding and analysis techniques for predicting when liquefaction is going to occur during future earthquakes. 

ROBERTSON: So, Japan was Ben’s first trip. Since then, he has been to Napa, California, where conditions were very similar to what we might see here in Oregon. He also spent two years going back and forth to Nepal. More recently, he was the team leader for a group called the Geoengineering Extreme Events Reconnaissance Association, which is funded by the National Science Foundation.

MASON: So, we went to Indonesia in 2018 following the damaging earthquake, as well as tsunami that occurred there. In that particular case we examined three very large flow slides. So, a flow slide is when the soil completely loses its strength. Very similar to the liquefaction phenomenon I explained earlier and then rapidly flows downhill. And so, what was interesting in this case is that these flow slides occurred on not very steep slopes. And so, we had a tremendous opportunity to learn about that phenomenon with, of course, the hope that what we're going to take away from it is going to help save lives in the future when similar types of phenomenon occur.

ROBERTSON: One of the techniques Ben uses to collect data involves some sensors in the ground called geophones, and a sledgehammer. It sounds odd, but it’s a technique that the petroleum industry uses that scientists have adapted for earthquake reconnaissance. 

MASON: All the geophones do, is they measure the velocity of the ground,

[MUSIC: “In Your Face” by Poddington Bear, soundofpicture.com.]

how quick the ground's moving. And they, they usually measure that velocity and we, we call it three components, but it's, it's just three directions. And so, you just think about like up and down and then two horizontal directions that are perpendicular to each other. And so, we usually use an array of them, or a line of them. So, we might use 10 of those geophones in a line, and maybe they’re spaced one meter apart, something like that.

And then you're going to some, some distance away from that. You're going to put a big steel plate on the ground, and you're going to hit it with a sledgehammer. And what that does is you're, you're kind of, you're trying to replicate what an earthquake is going to do by smacking that steel plate with the sledgehammer. You're sending the waves into the ground, and then they're gonna make their way through the ground. And they're going to meet different layers of soil. And as they meet those different layers, they're going to bounce back up and come to the surface. And it's going to be this very complicated picture of how the waves go into the ground and how they ultimately come back up. But with those little velocity sensors, or geophones, that's exactly what we're measuring, we're measuring the velocity of the wave as it comes back up.

And we're also measuring the time that it takes after I strike that, that plate with the sledgehammer. And from those pieces of information we can use what's called an inverse technique and work backwards to estimate how the soil must be layered in the ground. 

ROBERTSON: Ben also using newer techniques, such as remote sensing technologies. 

MASON: In Indonesia, we brought a couple of drones over with us with very high megapixel cameras and we're able to program in flight paths so that they would stop on certain spots and take high-quality imagery. And we're also able to put out these very sensitive GPS sensors, leave them running for a couple hours. We left them running at very known locations with targets. And so, as the drone flies over and images those targets, and then from the GPS data, you know exactly where on Earth you're located as well as the elevation.

And so, from all of that information, we're able to piece together very accurate — they're called digital elevation maps or digital elevation models. And so, it's a very accurate representation of the ground surface, and you can do it for buildings. And we have a number of colleagues at OSU, for instance, Michael Olson, who do this type of work. Ultimately, what we're trying to do in earthquake engineering, though, is measure how things move. And so, I think, we're, we're either taking displacement measurements, or velocity measurements, as I've described before, or even in some case, acceleration measurements.

ROBERTSON: OK, cool. And so, if you understand how the earth is going to move, you can predict what will happen to buildings and then try to, um, engineer things in a way so that they are less impacted. Is that correct? 

MASON: You would've gotten an A, in my geotechnic earthquake engineering class. I mean, if, if there was a better, there's not a better summary. There's nothing more important to us than understanding how the ground is going to move during an earthquake at the specific location of wherever our building, bridge, earth dam, pipeline, what have you, is located. If we know how the ground’s going to move, and in other words, how it's going to displace, what its velocity, what its acceleration is going to be, we can now predict how the structure is going to respond. So, the, maybe the Holy Grail for this work in Oregon now, because we haven't had a major Cascadia earthquake since 1700, is trying to predict how the ground is going to move throughout the Willamette Valley during the next earthquake. And so, if I was going to make a plea for the state putting resources into science, that would be one of my big pleas is let's put money into that. And certainly, we have colleagues at OSU, I've got a lot of colleagues at the USGS that are working on, on this problem. But it's a hard problem. But if we get it right, or if we get it anywhere near right, it's going to pay dividends in terms of making our infrastructure safer.

ROBERTSON: To reach that goal, Ben discovered that his data collection improved if he did one simple thing — talk to the people who live there.  

[MUSIC: “Creeping Up on You” by Godmode, part of the YouTube Audio Library, licensed under Creative Commons.] 

MASON: My first reconnaissance trip, I thought it was just all about, uh, you go in here's the scientific objective, you do the work and you get out. What I realized very quickly is that that was not the best strategy. But it's a strategy that's been employed for a long time. The first time I went to Japan, we went up to this farmer's land that has liquified, and scientists have been coming out to his land, he told us since the 1970s to do similar types of work. Of course, the sensors and the processes have advanced over the years. And he actually said, we are the first team in that entire time to talk to him.

And so, I gave him my Oregon State hat at the time and he gave us a bag of persimmons as, as a trade. And so for me though, I think the, that interaction set the tone because even through that brief interaction and we had the students there translating. What we realized is that we learned an incredible amount and he pointed us to other areas where we didn't realize that liquefaction had occurred. And so maybe in some sense, I was fortunate in my first real reconnaissance experience that I also had that experience. And ever since then, I've I brought voice recording capability with me to the reconnaissance events to try to capture as much of the eye witness interviews as possible.

ROBERTSON: Including the step of talking to witnesses turned out to be crucial for his most recent trip to Indonesia.

MASON: When we got there, we didn't have the best recordings of how the ground actually shook from seismometers. And so, we talked to people about their experiences of how the ground shook, and then over talking to say, 30 people, the description was very, very consistent, and that was critical for us and piecing together how these flow slides initiated and how they occurred and how they might occur again in future events.

ROBERTSON: One of the things Ben finds rewarding about his job is the opportunity to communicate with people. Part of the research he did in Nepal was providing workshops and guidance for the engineers and scientists there. More recently, he has been working to educate the local community in the Willamette Valley through op-eds and workshops for the general public explaining the science behind earthquake hazards and guidance on how to prepare. This year, Ben has a position with United States Geological Survey, known as the USGS, as a research civil engineer where he hopes to expand his reach with science communication. You can read his op-eds that are linked on our webpage to learn more, but here are the two main points he wants to convey. 

MASON: Don't have the false sense that because we're a fully developed nation that we're somehow, um, we don't have the same risk. The earthquake does not care about our economic status. And we saw a bunch of damage in Japan, who's also a fully developed nation. So, I think that's one lesson. I think the other one is: Go ahead and start talking in your communities, because right now, interaction with your community members is in some ways, uh, optional, right? You can go about your day-to-day life without interacting with any of your neighbors. But during these post-disaster times, that's not going to be really an option. So, to the extent that you can start interacting with your communities, and then in particular, figuring out, you know, for me, one thing I could probably do is go around and help turn gas valves off, for instance, but other folks might have, uh, other skills. But this all happens naturally after one of these disasters. But I think to the point that we can educate ourselves and prepare beforehand, even when that community building and coming together does happen, it can be stronger.

[MUSIC: “Future Rennaissance” by Godmode part of the YouTube Audio Library, licensed under Creative Commons.]

ROBERTSON: We covered all my questions. Is there anything else that you feel like we didn't cover that important that you feel is important to add?

MASON: I think, the one plea I’ll add is that whenever you're interested in something new, that seems hard, there's maybe a reluctance to get involved, and there's like, um, a perceived barrier to get involved. You know, for instance, if you want to play golf and you go out to the golf range and you see people who are hitting the ball 300 yards, that can be a tremendous barrier to you wanting to start that because you know that you're not gonna be able to do that. And maybe you're embarrassed that other people are watching. And so sometimes I think that science and engineering is kind of like that for people when they're young. And, and one thing that as I've gotten older, one thing that I would like to, to shout more about is that there's large room and science and engineering for, for everyone. And, and indeed, as we move forward and think about solutions to our infrastructure problems, we would be better served if more people are involved. 

One thing that I think surprises a lot of people when they do become scientists or engineers is ultimately, I spend most of my days writing or talking to people. So, communication, if you're a very effective communicator, you can be an exceptional scientist or engineer. And the other misconception that that comes about is it's gotta be an individual pursuit. Like you've got to be great at all of these things. And I think that's, that's complete nonsense, right? We should be working together. And the folks who are better at communicating should do that part of it, the folks who are better at sitting down and programming and doing the math should do that part of it. And so, for anyone listening, that's maybe interested in science or engineering, or has, uh, kids or nieces, nephews, et cetera. You know, I just really encourage them to not think that there's a barrier up. As we move forward. I think the inclusion of more folks into this field as what we need.

ROBERTSON: Perfect. Thank you. Good.

[MUSIC: “Broken Drum Machine” by Godmode part of the YouTube Audio Library, licensed under Creative Commons.]

ROBERTSON: That concludes the second episode in our season on natural disasters, up next we take on wildfires. This episode was produced by me, Rachel Robertson, with lots of help from Will Havnaer and the whole podcast team. 

Our intro music is “The Ether Bunny” by Eyes Closed Audio on SoundCloud, used with permission of a Creative Commons attribution license. The music and effects in this episode were also used with appropriate licenses. For more information, visit engineeringoutloud.oregonstate.edu.

ROBERTSON: Okay, cool. I think we just had a bird visit us. 

HAVNAER: We did. 

MASON: I like birds. 


Featured Researchers