Exploring the Depths, Earthquakes and ‘The Big One’ Dean Livelybrooks

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Photos by Bill Purcell

“I’m a marginal guy,” chuckles University of Oregon geophysicist, Dean Livelybrooks.  A leading scientist with the Cascadia Initiative, which studies earthquakes, Livelybrooks often works right on top of the margins where “the big ones pop.” His globe-trekking fieldwork includes climbing glaciers, straddling the San Andreas Fault, and shielding his instruments from bears and stampeding elk.

We caught up with Livelybrooks in Astoria, aboard the Navy-Woods Hole research vessel, Atlantis. He had just returned from helping recover thirty seismometers—each about half the size of a compact car—from the underwater fault line between the Juan de Fuca and North American plates.

We learned that Livelybrooks has not only helped discover what the big one will look like, but he may be closing in on the more important data point—when.

 

What was it like to work on the Atlantis, the mother ship to those famous submersibles, Alvin and Jason?

It’s an adventure where you bond with your teammates, learn to work together effectively, and try not to get seasick! I remember one day of spectacular weather, where the sea was flat, and had changed from metallic grey to azure blue. It just hit me how great it was to be onboard! We were about 150 miles out to sea with a crew of forty-six, retrieving the seismometers that had been collecting data for the past year. As we cruised along, we also made bathymetric (elevation) maps of the sea floor and used that to map bubbles associated with volcanic vents. The information is uploaded promptly to a national data repository. One of our fundamental questions is how the next major earthquake off our coast will occur, an event likely to match recent earthquakes and tsunamis in Japan and Sumatra. This information can then be used to help planners minimize impacts on society.

How do you retrieve a 1,500 pound seismometer at sea?

We use a clever device, called a ‘burn wire,’ which releases weights attached to the seismometers. The engineers sonically tell the ocean bottom seismometers to put electric current down a wire with a segment of its insulation stripped, so that bare wire is exposed to salty seawater. The electricity causes rapid corrosion of the wire, it breaks, and either the seismometers float to the surface or let loose a buoy tied to the instrument.

Other ocean bottom seismometers are recovered only by the remotely-operated vehicle, Jason. Those are the most fun. We sat in the dark control room, watching the many monitors showing deep water scenery, and the ‘elevator’ used to recover the seismometers. We got to hang with the ‘cool kids,’ the crew that uses joysticks and computer screens to pilot Jason, manipulate its robotic arms and move Atlantis around via GPS ‘spoofing’. Fun stuff!

Next summer, after your fourth voyage for the Cascade Initiative, you’ll have amassed four years of data. What do you think it will show?

(His eyes widen.) We’ll know much more about the kind of big earthquake we will have. We’ll find previously-undetectable small earthquakes associated with deformation of this zone, new active faults, and detect small changes in water pressure associated with the flexure of the ocean floor. Large distant earthquakes create seismic sound waves and we can use that information to probe the ocean crust. We may even detect evidence of ‘slow earthquakes’ at the leading edge of the North American plate.

This may be the first time a lot of people will learn about small earthquakes, and how they may help forecast the big one.

Right now it’s a working hypothesis. Imagine a magnitude 6.5 earthquake going off below you, and you don’t even know it, because the shaking and deformation are stretched over a few weeks instead of minutes. Slow earthquakes are energy-equivalent magnitude 6.5 events that happen over several days, episodically about every ten to fifteen months. They’re twenty-five miles deep and stretch from Victoria, Canada to Port Angeles down through Aberdeen and south to Eugene. Our seismometers on the ocean floor will help us determine if slow earthquakes are happening there, too. These quakes enable slipping, east of where the two plates are stuck together. Some scientists think that these slow earthquakes serve to put more load, called stress, on the locked zone, which makes it more likely to pop. In the extreme, imagine one last slow earthquake pushing the locked zone over its limit—stressing it out—and triggering a massive earthquake.  

How does your ocean field work intersect with what you’re doing on land?

We’re setting a 200-mile-long grid of magnetometers and electric dipole measurement equipment in the coastal range, from Coos Bay, Oregon to Aberdeen, Washington. These magnetotelluric measurements tell us how the earth conducts electricity, and we can use the data to make conductivity models in three dimensions. Conductivity reveals the presence of fluids where the two plates meet. These fluids help bits of the ocean crust melt when dragged to great depths and pressures below the Cascades’ volcanoes. We’re interested in what role fluids play in the rock-cracking associated with those slow earthquakes.

Magnetotellurics—studying the electrical structure of the earth and how well it conducts electricity—is your specialty. What else is it teaching you about earthquakes?

If you were to look at a highly magnified image of a microchip, you would see structures that were made to control the flow of electricity at microscopic scales, using small currents to control much larger currents. In magnetotellurics we try to develop a similar picture of the Earth’s crust, looking for natural structures, plate boundaries or fluids under volcanoes, that control current flow. Currents are created in oceans, and they try to drain through bordering continental rocks. Just as with microchips, a small change in electrical structure—think of it as flipping a switch—can lead to redistribution of current flow. My theory is that pockets of fluids along faults rupture just before an earthquake. So with magnetotellurics, we’re looking for changes in the current flow, potentially signaling an earthquake. Our models have detected these changes.

Using magnetotellurics, you were among the first to create a 3-D model of the structure of the North American and Juan de Fuca (ocean) plates. Why was that a breakthrough?

In the 1980s, we acquired magnetotelluric data on a line from Lincoln City to near Redmond. For the first time, it supported the hypothesis of ‘low-angle subduction,’— that the young oceanic plate, created a few hundred kilometers offshore, is pulling under the Pacific Northwest at a low angle making it more likely to ‘stick’ to the North American plate over a greater area. That sticking part is what we now call the locked zone. Imagine pushing a rug across a sticky strip on a slick wood floor. The rug will bunch up at the sticky spot, what we call `deformation.’ This is like the plate margin in Cascadia. Now imagine that the rug will bunch up more until it finally lets go and slides. That’s analogous to the very large, but less frequent earthquakes that we have in the Pacific Northwest. This situation is also found elsewhere in the world, like Indonesia and Japan.

How does all your research help us prepare for the big one and save lives when it strikes?

By studying deformation of the leading edge of North America, the size and north-south variation of the locked zone, and what takes place at depth landward of the locked zone, we hope to constrain what might happen during a large Cascadian earthquake. How much shaking will there be? What is the maximum tsunami that might occur? The city of Seaside, for example, is considering building a structure on stilts to provide last-resort safety in case of a large tsunami. Another question is, how tall do you make the stilts to ensure those in the structure stay above the surging waves?  We hope to give guidance about that.

Your research will tell us more about how bad our earthquake will be. What do we know right now?

 The best evidence still comes from the tsunami recorded on the coast of Japan in 1700, when the last big one popped. The entire subduction zone (where the two plates meet about 50 miles off the Oregon coast from Northern California up to Vancouver Island) went in one fell swoop—a large piece of earth! It was a 9 magnitude or greater earthquake, with considerable shaking inland. In theWillamette Valley we worry about resulting soil liquification. Certain pockets will turn to liquid and any structures sitting on that will sink. Examples would be along West 11th in Eugene and next door to our new hospital in Springfield. The hospital was designed to withstand that. Another concern is what we call ‘focus spots’—areas of intense shaking due to valley basements bending sound waves coming from the earthquakes. Buildings on those spots will fall, but a mile away, nothing. The shaking could last for minutes but it will feel like an eternity and there will be scary aftershocks.  It’s double jeopardy for people on the coast. You have to survive the shaking and then hike to high ground, all within about twenty minutes.

Do you have an earthquake preparedness kit at home?

In the words of my former colleagues at the Ecole Polytechnique du Montréal, certainement!

You’ve helped catalyze interest in STEM (science, technology, engineering and math) careers in Oregon. Tell us about that.

My colleague in the UO Chemistry Department, Dave Johnson, and I started a National Science Foundation graduate/K-12  program in 2002. We placed graduate students alongside K-8 teachers, using hands-on science kits and providing mentoring and role models for teachers and students throughout Oregon. The graduate student fellows become better teachers and communicators, some even living there as scientists-in-residence. Over its ten year run, GK-12 has worked with fifty-five schools and 230 teachers and we’ve seen some state science test scores increase.

We also started a program with six Oregon community colleges where rising second-year students—many first-generation college attendees and other underrepresented students—undertook a ten-week-long research project at the University of Oregon. They returned to their campuses as ambassadors of science to persuade other students to follow STEM career paths. This worked so well that we hope to restart this program statewide.

All that as the first generation in your family to attend college, and that at MIT.  You’re also passionate about your music (string and electric base), which you played on board the Atlantis.

I enjoy the creative opportunities in both performing music and doing science. It’s interesting that many of the UO physics majors I advise are also musically-inclined, some are double majors in physics and music. On the Atlantis, I found that many among the science and ship’s crews were musicians. We accompanied Mother Nature in a great rendition of `Stormy Weather.’

Magnetotellurics—studying the electrical structure of the earth and how well it conducts electricity—is your specialty. What else is it teaching you about earthquakes?

If you were to look at a highly magnified image of a microchip, you would see structures that were made to control the flow of electricity at microscopic scales, using small currents to control much larger currents. In magnetotellurics we try to develop a similar picture of the Earth’s crust, looking for natural structures, plate boundaries or fluids under volcanoes, that control current flow. Currents are created in oceans, and they try to drain through bordering continental rocks. Just as with microchips, a small change in electrical structure—think of it as flipping a switch—can lead to redistribution of current flow. My theory is that pockets of fluids along faults rupture just before an earthquake. So with magnetotellurics, we’re looking for changes in the current flow, potentially signaling an earthquake. Our models have detected these changes.

Using magnetotellurics, you were among the first to create a 3-D model of the structure of the North American and Juan de Fuca (ocean) plates. Why was that a breakthrough?

In the 1980s, we acquired magnetotelluric data on a line from Lincoln City to near Redmond. For the first time, it supported the hypothesis of ‘low-angle subduction’—that the young oceanic plate, created a few hundred kilometers offshore, is pulling under the Pacific Northwest at a low angle making it more likely to ‘stick’ to the North American plate over a greater area. That sticking part is what we now call the locked zone. Imagine pushing a rug across a sticky strip on a slick wood floor. The rug will bunch up at the sticky spot, what we call ‘deformation.’ This is like the plate margin in Cascadia. Now imagine that the rug will bunch up more until it finally lets go and slides. That’s analogous to the very large, but less frequent earthquakes that we have in the Pacific Northwest. This situation is also found elsewhere in the world, like Indonesia and Japan.

Last question Professor is about your name. We could find only two people in the USA named Livelybrooks—you and your wife.

The simple story is just that my wife’s last name was Lively and mine was Brooks, so we just made up one name and that way so neither of us gave up our names. It’s just a sweet marriage thing.

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