Fieldwork rocks: From sea to quaking sea
Seismologist Margaret Boettcher has ventured to the depths of South African gold mines and the middle of the Pacific Ocean in a quest to find earthquakes that are predictable enough to measure and simple enough to understand. Performing fieldwork in these locations presents unusual challenges, such as being so crammed in an elevator shaft with miners that Margaret’s feet couldn’t touch the bottom, and dredging rocks from the seafloor using a bucket on a 3.5-kilometer-long cable. On Margaret’s most recent series of expeditions to the Gofar transform fault 1,500 kilometers west of the Galapagos Islands, she and many of her team members couldn’t even join the cruises due to the COVID-19 pandemic. Instead, they worked out ways to participate remotely, which had the added benefit of opening up the research to more people.
This episode was produced by Katrina Jackson and mixed by Collin Warren. Artwork by Jace Steiner.
Transcript
Shane Hanlon: 00:00 Hi Katrina.
Katrina Jackson: 00:01 Hi Shane.
Shane Hanlon: 00:03 Yeah, so this is a little different. So for folks who listen regularly, they might notice that this is not Shane and Vicky. Vicky is unexpectedly away and shall be for a while, but recording must go on. So I have enlisted the help of one of our fearless producers, Katrina Jackson. Hi Katrina.
Katrina Jackson: 00:24 Hi Shane.
Shane Hanlon: 00:25 Yeah, so I’m just going to ask you a thing and we’ll see how it goes. See if Vicky would be proud of us or if she’ll just never want to leave again. So, question for you. How deep underground have you been, ever?
Katrina Jackson: 00:45 I’ve been caving, I’ve been spelunking, but it’s been a long time and I don’t know how far down it was. Probably wasn’t very far.
Shane Hanlon: 00:52 Okay. Are we talking wild caving when you’re squeezing through small crevices?
Katrina Jackson: 00:57 Yes.
Shane Hanlon: 00:58 Oh, that makes me claustrophobic a little bit.
Katrina Jackson: 01:05 Yeah, I haven’t done it since I was… I did a couple trips back in Girl Scouts, so it’s been a long time.
Shane Hanlon: 01:17 Yeah. So for me, I don’t have a good answer for this. I’ve been in big caves, monster caves. I’ve been in Mammoth and touristy, you stand up in caves. I do know I was in Boy Scouts, similarly. My older brothers were as well and they stopped going caving by the time I came around for no specific reason, but they tell me these stories of they would be going into caves that probably didn’t have the right to be going into if I’m being… Not from a legal standpoint, but they had no business being in. So there was one time where we were going through and one of us got stuck.
Katrina Jackson: 01:53 I know.
Shane Hanlon: 01:53 And had to just pull and hope for the best, and that is not an experience that I want or would relish. And so in this case, I’m happy that I didn’t get to have that experience.
Katrina Jackson: 02:05 Yeah. Have you seen all those specials about the Thailand cave rescue?
Shane Hanlon: 02:12 Oh, yes.
Katrina Jackson: 02:12 Yeah. Me too.
Shane Hanlon: 02:12 Hard pass on my end.
Katrina Jackson: 02:14 Right. That’s not something I would want to experience.
Shane Hanlon: 02:22 Science is fascinating, but don’t just take my word for it. Join us as we hear stories from scientists for everyone. I’m Shane Hanlon.
Vicky Thompson: 02:22 And I’m Vicky Thompson.
Shane Hanlon: 02:33 And this is Third Pod from The Sun. All right. So why are we talking about being underground or caving or anything like that? I assume there is a connection here.
Katrina Jackson: 02:47 Yes. So underground spaces connects to some of the research that our guest today talks about. So for this episode, I talked with Margaret Boettcher and she’s an Affiliate Research Professor for the University of New Hampshire, although she’s actually located in Australia, and Margaret is a geophysicist, more specifically a seismologist.
Shane Hanlon: 03:07 Oh. So we’re talking earthquakes. I’ve always been interested about how one does field work with earthquakes. They’re hard or impossible to predict. Right? The next big earthquake on the West Coast could be tomorrow, it could be 50 years or whatever. We just don’t know. It’s not like when an earthquake starts, you can send scientists to go study it since it’s usually over within a few seconds.
Katrina Jackson: 03:32 Yes, very true. But I did learn from this conversation that there are some types of earthquakes that actually are more predictable and so they’re therefore easier to study in person.
Margaret Boettcher: 03:48 So I do try to study relatively simple earthquakes where I can. I try to study earthquakes where I can constrain at least some aspects of where they start. Mines where we know a lot about the rock type and the temperature, and if there’s damage in the fault zone, we can put a seismometer very close to those earthquakes so we can get a pretty simple picture of what those earthquakes are like. And I also like to study earthquakes on oceanic transform faults because they’re pretty simple. We can see that they occur very regularly and we also know again about the types of rocks that they occur in, and we can see how long their faults are and we can calculate the thermal structure of the fault. So again, we know a lot of the conditions at which they occur.
04:39 I’ve also studied, I’ve also done some laboratory experiments in my past to try to understand earthquake friction and to generate some earthquakes in the lab. And again, we know a lot about those. We can really constrain the rocks that we’re using and the temperature and the stresses that we’re applying to create these earthquakes. So if we can reduce some of the unknowns, then we can really try to figure out what we do know about earthquakes and we can apply what we know from these relatively simple situations to the more complex places on earth if we can. That’s the ultimate goal.
Katrina Jackson: 05:21 So how do you go about measuring all these earthquakes? Do you need to go out and get sensors in these locations? What does that look like?
Margaret Boettcher: 05:30 Yeah, so there’s a global network of seismometers where people have put seismometers and there’s a lot of data sharing. So there’s a global network where we can get information about earthquakes that are large. But if we’re interested in looking at smaller earthquakes, then we need to really put down seismometers very close to where they occur because the seismic shaking from those earthquakes won’t travel nearly as far. So I’ve been involved in putting seismometers in different locations throughout the world. The first time I ever was involved in a seismic experiment was in China, and we covered a wide region there to understand the structure of a volcano on the border near North Korea. And since then, I’ve been involved in a number of other projects.
06:22 One place that I’ve studied earthquakes quite a bit is in South African goldmines. So this is a place where they’re relatively simple. It’s a relatively simple situation because you can look at an earthquake that occurs only a number of meters or hundreds of meters away because you can go down into these mines and put seismometers down in them, and there are seismometers already down in those mines. So places that have lots of earthquakes.
Katrina Jackson: 06:55 So the earthquakes and the mines, are those from the mining or is it from [inaudible 00:07:02]?
Margaret Boettcher: 07:01 In general, they are from the mining because if you put a large hole in the ground, that really disturbs the stress field and the rocks want to collapse inward. And so that often causes a lot of seismicity. So some of the mines that I’ve worked in are some of the deepest in the world, about four kilometers deep. Yeah, it is amazing. One of your one questions had to do with some favorite field work story and that was one that came to mind was when we were doing a seismic experiment in one of these mines and just getting down under the ground and being able to actually touch a fault in situ is really amazing, but the whole process of getting down there can be quite exciting.
07:48 So one thing, you go down in a shaft. So it’s like an elevator, but it’s this really big… It’s a three-storey cage they call it, and it really is a lot like a cage. They just really shoved people in. And one time I didn’t even have my feet touching the ground anymore because they just keep shoving people in and with a backpack on, I lifted up, and then you start going down and first you can feel the temperature getting colder as you get away from the earth’s atmosphere. And then it starts to get hotter and hotter as you get down more than three kilometers. And then you get out and it’s very hot and humid because of the ambient conditions, and that part of the earth would be full of water, but the mines have to continuously dewater it so that there’s not as much water everywhere.
08:44 And they also do condition the air to put more oxygen in and reduce the temperature, but still it’s about 85 degrees and a 100% humidity. And then we walk about a kilometer to our chosen site carrying seismometers and car batteries to power the seismometers and install the size the seismic station, and then it will record… One of our experiments, we only recorded for about two weeks, but we had many, many earthquakes in that time period and had many magnitude 2s. And those were the largest earthquakes that occurred, two-and-a-half during that two week time period. And we did feel in earthquake underground, which was pretty interesting, and it sounds like a big, big bang rather than… I didn’t really feel too much shaking, but the noise was the main thing of interest.
Katrina Jackson: 09:43 So I’m guessing by studying these human made smaller earthquakes that know are going to be happening because of the mining activity, that helps you basically understand how shaking happens throughout certain types of rocks. Is that the idea there?
Margaret Boettcher: 09:59 Yeah, yeah. There’s a lot of reasons to study those earthquakes. One is trying to understand if large and small earthquakes really are the same because there’s so many more small earthquakes. So if they have the same sort of mechanism and just a different amount of energy release, then that’s very helpful in terms of understanding how earthquakes work in general. So the size of an earthquake in a mine is right in-between what we can make in a laboratory and what happens on a natural fault.
10:31 So trying to span that gap and trying to understand if we can use what we learn in the laboratory and directly apply it to the natural fault zone is one way to do that, is to fill in that gap with mining sized earthquakes. Another thing that we want to try to understand is trying to understand if natural and human-induced earthquakes really have the same sort of mechanisms also. And so this is a place that we can look at that.
Shane Hanlon: 11:08 As previously mentioned in the top of this episode, I can’t imagine going into an active goldmine that’s up to four kilometers deep and experiencing a… One, doing that and two, experiencing an earthquake big or small while I’m down there. You mentioned that you’ve been in mines before. How does that compare to any undergone experiences you’ve had?
Katrina Jackson: 11:33 Yeah, I’ve been to a few mines on public tours. I think I’ve been to a copper mine in Arizona and there’s an iron ore mine in Northern Sweden. And I’ve also been to a gold mine over in the Black Hills of South Dakota, but they turned that into a whole science laboratory. I think they’re doing neutrino experiments and all sorts of things there. But yeah, getting back to earthquakes.
Shane Hanlon: 11:57 Oh right, yes. Earthquake. Yes, that’s what we’re talking about. So seismologists like Margaret go into minds because they know there’s definitely going to be at least a little bit of shaking and seismic activity in air because we’re literally doing, or we’re literally drilling holes into the crust. But I wondered what was the other place she mentioned at the beginning where she likes to study earthquakes, something about oceanic transform faults?
Katrina Jackson: 12:23 Yes. Fault lines that are way out in the middle of the ocean.
Margaret Boettcher: 12:27 Much of my work has been on oceanic transform faults. So we mentioned what a transform fault was before where one side of the plate boundary slides horizontally passed the other side of the plate boundary, and oceanic transform faults are obviously in the ocean and these are some of the most regular faults that we know of. Some of the ones that I’ve studied most are quite fast slipping, so they’re the fastest slipping faults and they have very short seismic cycles. So the largest earthquake happens quite regularly. So that makes them much more easy to study a full seismic cycle, whereas a full seismic cycle on the San Andreas might be something around a 100 years or more. On an oceanic transform fault, it’s about five years on the fastest slipping ones. So that’s much more manageable in a seismologist lifetime to study many cycles.
13:25 So that’s one reason that I’m very interested in these faults. We know that the largest earthquakes on these faults are quite small, so the largest earthquakes and some of the fastest slipping faults are only magnitude six. And they have these regular, fairly small earthquakes, magnitude six earthquakes that happen about every five years. And in 2008, we went out and had an experiment on these faults, on one of these faults called Gofar transform fault. And from looking at the tele seismic record of the seismicity, we knew that we expected another magnitude six to happen in a particular location pretty soon. And so we put our seismometers in that location and found an incredible… We had a one-year experiment and had an incredible dataset where we found thousands and thousands of earthquakes preceding the magnitude six, but not located in exactly the same spot, located in an adjacent portion of the fault. And that portion of the fault never has large earthquakes.
14:32 So we have parts of the fault that have the magnitude sixes separated by parts that we call rupture barriers that don’t have magnitude sixes. And the rupture barriers actually were the place on the fault that has the most tiny little earthquakes. So it was surprising to see that there’s this place that doesn’t have big earthquakes, but it has the most little earthquakes.
Katrina Jackson: 15:02 So these magnitude six earthquakes along these oceanic transform faults, are they noticeable at all from above the sea? Do they cause any waves, tsunamis or effects on islands or anything?
Margaret Boettcher: 15:16 Not really. So actually, I think these are the best places to… You can really root for the earthquakes to happen because they have no societal impact. So because there’s no vertical offset on these faults, they just move horizontally, they don’t cause any tsunamis. And because they’re very far from land, they really don’t affect people in any ways.
Katrina Jackson: 15:41 So how did we first learn that these earthquakes were happening along these oceanic transform faults?
Margaret Boettcher: 15:48 Yeah. Well, we can see them from the global set of seismometers. So you can see magnitude six earthquakes that happen anywhere on earth. You can really see down to magnitude fives or maybe four-and-a-halves or even fours in some places. But anywhere in the world that has a magnitude five or so earthquake, we’ll be able to record it with the global set of seismometers. So we could see the pattern that there were these magnitude six earthquakes occurring, and these faults had a few patches where these magnitude six earthquakes occurred, separated by patches where they don’t occur, but we didn’t realize that there were all these four shocks in-between, in these rupture barriers.
16:27 So then we put in a proposal to try to go back to the same fault and see if we could do this again and really get into the details of why this might occur and see if we could capture the same thing again. So this new experiment that we did between 2019 and 2022 involving three cruises. So we had a two-year ocean bottom seismometer experiment along with rock dredging and mapping with the autonomous underwater vehicle century, which also looked at the water column to identify whether there was any interesting signals coming from hydrothermal fluids coming out of the fault zone. And we also had an electrical conductivity study as part of the project too.
Katrina Jackson: 17:17 So all the vehicles you’re putting underwater for studying the fault are autonomous, correct? You’re not having any crude submarines or anything?
Margaret Boettcher: 17:24 Right. So we just had really one autonomous underwater vehicle, which… Well, actually two, you’re right, which was sentry, which we were able to map and very high resolution and take photos of the fault zone and record about the near water chemistry, water column properties as well.
Katrina Jackson: 17:46 Okay. So you’ve got the autonomous vehicle taking the images, doing the mapping. You mentioned rock dredging. What’s that?
Margaret Boettcher: 17:54 Yeah, so that’s really… You just put a bucket with some scraping devices over the side of the ship and drag it along in a particular track up a hill and scoop up some rocks.
Katrina Jackson: 18:09 About how deep is the sea floor in this area?
Margaret Boettcher: 18:13 About three-and-a-half kilometers in much of the fault.
Katrina Jackson: 18:18 All right. So that’s like a bucket on a really long [inaudible 00:18:21].
Margaret Boettcher: 18:21 It is. A really long cable, yes. And so that can be a challenge. Some of the ships are hesitant to do this because there can be pretty large tensions on the cable, and so that can potentially be dangerous if it’s going to snap or break.
Shane Hanlon: 18:48 Three-and-a-half kilometers deep. That’s got to be a far way down. So I’m wondering, where is the go far transform vault?
Katrina Jackson: 19:00 So I read that it’s about 1,500 kilometers west of the Galapagos Islands.
Shane Hanlon: 19:06 Oh, okay. So out in the Pacific Ocean. I was just in Galapagos last year. That’s really out in the middle of nowhere, and I can’t even really picture that. And so the most recent series of cruises was from 2019 to 2022. I imagine… Oh no, I was thinking about the pandemic. I remember reading in the… There was a recent AGU Eos article in our news magazine about how the pandemic actually affected their expedition.
Katrina Jackson: 19:41 Yes. And so of course, Margaret talked about it with me as well in our interview.
Margaret Boettcher: 19:46 Well, so the pandemic ended up giving us some interesting challenges because we had put out these seismometers. So we dropped the seismometers over the side of the ship and left them there. We needed to collect them within 12 to 14 months of when we deployed them. And unfortunately, our location is very remote and it’s quite far from especially any US port. So we were deemed a very high risk experiment and it wasn’t clear that we’d be able to go, but we did have this very valuable data. We knew the earthquake occurred and we wanted to be able to see all of the patterns of seismicity surrounding it. So luckily, we were able to go. There were many different iterations of when we’d go or where we’d go, who would go on board?
20:36 And in the end, we just had one scientist, the chief scientist, John Collins, who is also the lead of the Ocean Bottom Instrument Center for… So he’s really the ideal person to go on this cruise because we were picking up our 51 seismometers and redeploying them.
Katrina Jackson: 20:57 Yeah. So you didn’t end up actually going on these investigations. It was just the one lead scientist. How did you manage to stay involved remotely?
Margaret Boettcher: 21:08 Yeah. So the third cruise actually did have, I think a reasonable sized group of people, but it became a very large investigation with all the things that we had planned to do for the second cruise, got bumped to the third cruise because by the time we had the third cruise there was at least vaccines and things were loosening up a little bit with the pandemic. So that third cruise had all of the century work. So that was the autonomous underwater vehicle that was mapping the fault zone, and they have a crew who run that and they usually work with the scientists on board to plan the next dive each day just before it. And this is something that we decided was something we could do remotely. So a group of us, we had about six of us were regulars who were meeting each day in my time.
22:09 So we were spread around the world and in my time zone, it was 6:00 AM. So every morning I’d get up at 6:00 AM and meet with everybody who was mostly in the US, and it was in there late afternoon and plan the next dive. And we also had some dedicated students and postdocs on board who really worked with us very directly so that we were able to make sure that things that we were thinking weren’t out of line of what was going on on the ship. It can be intense out at sea. We had to make sure that everything that we were asking them was within what they were able to do and willing to do. And I would say that that was a really excellent experience for all of us who were involved because many of us who weren’t able to go to see were still able to really be involved in the field work remotely.
Katrina Jackson: 23:04 Was the ship able to get pretty strong signal for internet and connecting with you all?
Margaret Boettcher: 23:12 It’s actually in a pretty tricky spot. So in terms of satellite coverage, there just isn’t the great satellite coverage. So we didn’t have any Zoom calls or any sort of video calling the ship. We just relied on emailing and transferring some data as files.
Katrina Jackson: 23:35 Are there any approaches that you did in this expedition, these series of expeditions that you think might be helpful for remote science in the future?
Margaret Boettcher: 23:45 Yeah, I think that it was really excellent and very inclusive to have such a large remote part, and especially now that everybody gets together remotely all the time. There really shouldn’t necessarily be a barrier to doing that for much of this kind of remote science. So I think one of the lessons learned is we really need to have dedicated people on the ship that are going to be helping the remote… Whoever’s working remotely on land needs to have partners on the ship that they can really work with and everybody has to… We have to come up with a communication streams ahead of time so that the communication between ship and shore is very smooth because it would be easy for that to get out of hand and not be productive.
Katrina Jackson: 24:42 What are some ways in general that you’d like to see fieldwork be more accessible to a wider range of people?
Margaret Boettcher: 24:50 That’s a really good question because there are quite a few barriers to fieldwork for many types of people. It’s hard for people who can’t get away for a long time due to commitments that they might have with family or jobs, and it could certainly be challenging for people economically. Sometimes you have to… Putting your regular life on hold to go away can be quite challenging. So one of the things that we did was hire a number of people and pay them to go to sea. So paying people rather than just relying on students and postdocs, that opens up the field for more people to be involved. And in having remote options also allows many more people to be involved.
Shane Hanlon: 25:45 It’s great that they learned some ways to participate in field work remotely and get more people in fall, which makes me wonder, should we be calling it field work when it’s out in the middle of the ocean? Or we’ve also talked to the scientists who do research from planes, which again, that is not a field.
Katrina Jackson: 26:03 I think maybe you’re thinking into the word a little bit too much.
Shane Hanlon: 26:06 Oh man, me overthinking things, who would’ve ever thought? But regardless of the overthinking, getting more people involved, yes, is a very good thing.
Katrina Jackson: 26:17 Well, how about now we transition to learning a bit more about Margaret?
Shane Hanlon: 26:22 That’s probably a good idea.
Katrina Jackson: 26:24 How did you get into seismology?
Margaret Boettcher: 26:27 Well, I always really liked the outdoors and I also really liked math and physics and putting them all together led me to geophysics and I took a geology class when I first got to college and it was so interesting. So I was hooked right then. Another thing that I would encourage anyone who has the opportunity is to do research experience for undergraduates internships when they’re in college. And I was lucky enough to get to do many of these. I did one in Alaska and one in Hawaii and one in Bermuda. And then I did another internship when I was in China, and those really cemented my love of geophysics and traveling and seismology. And then going to graduate school, had to decide if I wanted to study the structure of the earth with seismology or if I wanted to study earthquakes themselves, the source of an earthquake. And I really was drawn to the societal impacts. So trying to understand earthquakes seemed like where I wanted to put my efforts just to try to help reduce seismic hazards and impacts, help reduce the seismic risks to society.
Katrina Jackson: 27:51 Well, it sounds like you’ve pretty much always been an outdoorsy person. Do you feel like you need to be to do what you do? I imagine it’s probably not too many seismologists and geophysicists who are like, “I’m an indoors person.”
Margaret Boettcher: 28:03 That’s right. Yeah. Of course, you can be an indoors person and you can be somebody who’s much more interested in sitting in front of a computer and coding. You can be an excellent seismologist that way but I like to think that you get a better overview of the whole process by being interested in going out into the field and seeing a fault and really getting a deep down sense of how powerful the earth is and how these faults work and the earthquakes that you’re studying. So it’s not necessary, but I think it is helpful.
Shane Hanlon: 28:47 Wow. Margaret interned in a lot of cool places just in her undergraduate. Did you get a chance to go anywhere cool when you were in college like that?
Katrina Jackson: 28:56 Certainly not as cool as Margaret. My only internships in undergrad were either at the school in Tucson or in Washington D.C. with the Smithsonian. So definitely nowhere overseas. I did do one field trip, a geology class in undergrad where we traveled… We went and saw different planetary analog sites between Tucson and San Diego. So that was kind of cool.
Shane Hanlon: 29:21 Wow. Yeah, that’s really neat. I loved my undergrad experience, especially the science part of it, but the most exotic place I went was rural Pennsylvania and just a different part from where I grew up. So that was good scientifically, but I wouldn’t exactly say that it was, let’s say, the most exotic of places. Well, we can’t, or we haven’t had quite those experiences, but we’re happy that Margaret sat down to chat with us. And with that, that is all from Third Pod From The Sun. I want to thank you, Katrina, for bringing this story to us.
29:58 This episode was produced by Katrina with audio engineering from Colin Warren and artwork by Jay Steiner. We would love to hear your thoughts on this podcast. Please rate and review us and you can find new episodes on your favorite podcasting app or at thirdpodfromthesun.com. Thanks all and see you next week.
30:23 It is amazing how basically I can turn into my own. It’s like I’m just doing face off with myself.
Katrina Jackson: 30:30 [inaudible 00:30:30].
Shane Hanlon: 30:34 You put enough filler words in that aren’t like and uh-hum, it works out okay.