Unlike the Pacific Northwest, the Atacama Desert in Chile experiences very little rain. But the two regions are both seismically active. Faults in the Atacama Desert are slowly sliding past each other in a way similar to the Seattle Fault in Puget Sound and the San Andreas Fault in California. The Atacama Desert’s lack of rain makes it easier to see how those gradual movements shape the landscape over time.

Alison Duvall, a 91̽�� associate professor of Earth and space sciences, and doctoral student will travel to Chile this month to study landscapes developed along these types of faults. Duvall has previously studied historic landslides at the site of the rainfall-triggered Oso mudslide and how rainfall, earthquake and landslide risks combine in Oregon.

91̽��News asked the two geophysicists about their upcoming trip as part of a new series, “In the Field,” highlighting 91̽��field research.

Where are you going, and when?

Tamara Ará�Բ��ܾ���-�鲹����: We will visit the , in the hyper-arid, or dry, core of the Atacama Desert in Northern Chile. The Salar is a dry lakebed that contains economic resources, in the form of salt, that is extracted from the basin and then exported around the world. We’ll be there Nov. 19-25.

We’re interested in this area because it’s extremely dry and has active faults slicing through it. Only a few places on Earth register such low rates of precipitation, offering a landscape that stores climate and tectonic variations from the past 50 million years. At our field site, there are places that haven’t seen a drop of rain in 500 years!

As a result, this is one of the best places on Earth to study how landscapes respond to earthquakes and plate tectonics under hyper-arid conditions. Dry conditions slow down erosion and help preserve landscape form and enable us to observe processes, like tectonic processes, that modify the surface from deeper down.

Have you visited this field site before?

TA: I visited this site last fall with , another doctoral student in the Department of Earth & Space Sciences.

Alison Duvall: This will be my first time to this site, to Chile and to South America.

What do you hope to learn there?

AD: We want to learn more about the dynamics of slow faults that move laterally — strike-slip faults, similar to the San Andreas Fault in California — and how these dynamics control the shape of the landscape. In wet places, it’s hard to isolate faults’ effects on the landscape since water is the main agent driving erosion. What we observe on the surface in other places is a combination of tectonics and surface processes. However, thanks to the aridity of this place, it is easier to be confident about what is changing the landscape.

We’re also interested in how this landscape has shifted with a changing climate. This place was wetter in the past, and there is evidence of climate change happening to make the region hyper-arid. So we are also studying how the landscape has adapted to that change.��

What’s something that you enjoy about this field work — especially something that might not occur to most people?

TA: There is a really special feeling when you’re in the driest place on Earth. It almost feels like you’re on a different planet. You don’t see any signs of life — no water, no animals, no plants — but it’s just amazing to feel that nothingness.

Changes in the landscape are so slow that when you visit the site, you know that each step you make, or any perturbation we make to collect our samples, can be one of the biggest modifications to the landscape in hundreds of years.

Anything you’d like to add?

AD: I’m super excited to get to this incredible field site and spend time with Tamara studying it. We have done field work together in New Zealand, and I have done decades’ worth of field work in many different geomorphic settings, but never in a hyper-arid landscape like this one. I can’t wait to see what we find!

The National Science Foundation has funded a multi-institutional team led by Oregon State University and the 91̽�� to work on increasing resiliency among Pacific Northwest coastal communities.

The new Cascadia Coastlines and Peoples Hazards Research Hub will serve coastal communities in Northern California, Oregon and Washington. The hub’s multidisciplinary approach will span geoscience, social science, public policy and community partnerships.

The Pacific Northwest coastline is at significant risk of earthquakes from the Cascadia Subduction Zone, an offshore fault that stretches more than 600 miles from Cape Mendocino in California to southern British Columbia. The region also faces ongoing risks from coastal erosion, regional flooding and rising seas due to climate change.

The newly established Cascadia CoPes Hub, based at OSU, will increase the capacity of coastal communities to adapt through community engagement and co-production of research, and by training a new generation of coastal hazards scientists and leaders from currently underrepresented communities.

The initial award is for $7.2 million over the first two years, with the bulk split between OSU and the UW. The total award, subject to renewals, is $18.9 million over five years.

“This issue requires a regional approach,” said co-principal investigator Ann Bostrom, a 91̽��professor of public policy and governance. “This new research hub has the potential to achieve significant advances across the hazard sciences — from the understanding of governance systems, to having a four-dimensional understanding of Cascadia faults and how they work, and better understanding the changing risks of compound fluvial-coastal flooding, to new ways of engaging with communities to co-produce research that will be useful for coastal planning and decisions in our region. There are a lot of aspects built into this project that have us all excited.”

The community collaborations, engagement and outreach will focus on five areas: Humboldt County, California; greater Coos Bay, Oregon; Newport to Astoria, Oregon; Tokeland to Taholah, Washington; and from Everett to Bellingham, Washington.

“We have a lot to learn from the communities in our region, and part of the proposal is to help communities learn from each other, as well,” Bostrom said.

The Cascadia hub is part of the NSF’s newly announced , an effort to help coastal communities become more resilient in the face of mounting environmental pressures. Nearly 40% of the U.S. population lives in a coastal county. The NSF established one other large-scale hub for research and broadening participation, in New Jersey, and focused hubs in Texas, North Carolina and Virginia.

The Cascadia hub will focus on two broad areas: advancing understanding of the risks of Cascadia earthquakes and other geological hazards to coastal regions; and reducing disaster risk through assessment, planning and policymaking.

“We’re not thinking only about the possibility of one magnitude-9 earthquake; this effort is about the fabric of hazards over time,” said co-principal investigator , a 91̽��professor of Earth and space sciences and director of the Pacific Northwest Seismic Network. “The heart of this project is merging physical science and social science with a community focus in an integrated way — translating scientific discovery with actions that coastal communities can use.”

The project intentionally emphasizes incorporating traditional ecological knowledge from the region’s Native American tribes as well as local ecological knowledge from fishers, farmers and others who have personal history and experience with coastal challenges.

“We are committed to co-producing research together with coastal communities and integrating multiple perspectives about disaster risk and its management,” said , an assistant professor in UW’s Department of Environmental and Occupational Health Sciences, who is co-leading the hub’s Community Adaptive Capacity and Community Engagement and Outreach teams.

“There are many dimensions to resilience, including economics, health, engineering and more,” said principal investigator , a professor at OSU. “This research hub is a way to bring together a lot of groups with interest in coastal resilience who have not had the resources to work together on these issues.”

The research hub’s other principal investigators are , a 91̽��associate professor of Earth and space sciences who will lead efforts to quantify the timing, triggers and effects of landslide hazards on communities and on landscape evolution, and , a professor of sociology at OSU. The other institutional partners are Washington Sea Grant, Oregon Sea Grant, University of Oregon, Washington State University, Humboldt State University, the U.S. Geological Survey, the Swinomish Indian Tribal Community, Georgia Tech University and Arizona State University.

For more information, contact Bostrom at abostrom@uw.edu, Ruggiero at 541-737-1239 or peter.ruggiero@oregonstate.edu and Tobin at htobin@uw.edu. See related press releases from and .

Researchers at the 91̽��, Portland State University and the University of Oregon have shown that deep-seated landslides in the central Oregon Coast Range are triggered mostly by rainfall, not by large offshore earthquakes.

The open-access was published Sept. 16 in Science Advances.

“Geomorphologists have long understood the importance of rainfall in triggering landslides, and our study is simply driving home just how important it is,” said first author , who did the work as part of his doctorate at the UW. “Our results show that more frequent, localized landslide events triggered by rainfall are just as important to consider as less frequent but more far-reaching Cascadia Subduction Zone earthquakes.”

Heavy rains are known to cause landslides that can be disruptive and deadly. A less frequent landslide trigger is a rupture on the geologic fault off the coast of Washington and Oregon that’s known as the Cascadia Subduction Zone — among a long list of concerns after a major earthquake. Landslide risks of all types increase if human development or wildfires remove trees, taking away the roots that stabilize the soil.

Recent research in Nepal and Japan, however, suggests that offshore earthquakes might not trigger as many landslides as previously believed. The new study finds a similar situation in the Pacific Northwest.

“We aren’t suggesting that the landscape had no response to these magnitude-9 earthquakes, but that the deeper-seated landslide deposits and scars out on the Oregon Coast Range hillslopes today were primarily triggered by precipitation events,” said senior author , a 91̽��associate professor of Earth and space sciences. “We conclude that past Cascadia Subduction Zone earthquakes triggered no more than a few hundred deep landslides during great earthquake events.”

The researchers used high-resolution aerial laser maps of the Oregon coast to look at 1,000 years of landslide activity. Landslides tended to happen in places with heavier rainfall, they found. But surprisingly, there was no detectable change in the number of deep landslides at the time of the large earthquake that shook the Pacific Northwest in 1700, or for two earlier offshore earthquakes that happened in roughly the years 1150 and 1470.

Duvall, LaHusen and co-author at Portland State University developed a method for dating landslides while studying the site of the deadly March 2014 mudslide in Oso, Washington. In that study, they used high-resolution images to view the surface roughness. Over time, soil settles and exposed rock erodes. The surface gets smoother, so surface roughness can be used to calculate a landslide’s age.

“The central Oregon Coast Range offered a massive, 10,000-square-kilometer natural laboratory to explore patterns in deep-seated landslide events through space and time,” LaHusen said. “It’s 50-million-year-old sandstone and siltstone that was deposited offshore, buried and compacted, and then uplifted to form the mountains we see today.”

Aerial with less than 3-foot resolution revealed 9,938 landslides inside the study area. Researchers narrowed those down to 2,676 landslides that have happened within the past 1,000 years, and then looked at the landslide frequency during that time.

For the new study, they applied their method to a larger area in the central Oregon Coast Range. To study landslide activity related to the Cascadia Subduction Zone, the researchers needed an area near the Cascadia fault zone with a consistent rock type and publicly available lidar imagery.

Researchers caution that the study doesn’t apply to shallow landslides, which frequently occur during earthquakes but leave no long-term evidence and can’t be analyzed with this method, or to different soil types, and so doesn’t necessarily apply to other regions. The research also didn’t consider shallower earthquakes from surface faults.

But the paper does support recent findings in Asia suggesting that offshore earthquakes don’t trigger as many deep landslides as once believed, and that rainfall may be the bigger factor in shaping the landscape over longer timescales.

“These data strengthen the point that we don’t need big earthquakes to trigger large and devastating landslides in Washington and Oregon,” Duvall said. “Seasonal precipitation and large rain events are important to focus on in landslide preparedness planning.”

This research was funded by the National Science Foundation and the Geological Society of America. The team began the work as part of the 91̽��, which is studying magnitude-9 earthquakes from the fault that runs parallel to the Washington and Oregon coastlines. Slips along this fault can lead to a so-called “Big One,” which last struck the Pacific Northwest in 1700.

Other co-authors are , , and at the UW; and and at the University of Oregon. LaHusen is now working at the U.S. Geological Survey in Mountain View, California.

For more information, contact LaHusen at seanlah@gmail.com or Duvall at aduvall@uw.edu.

The Pacific Northwest’s most recent large earthquake, the 2001 Nisqually earthquake near Seattle, was a magnitude 6.8, but history shows that the region could be rocked any day by a much larger event. At the American Association for the Advancement of Science’s annual meeting this week in Seattle, researchers from the 91̽�� and federal agencies will discuss the latest science on megaquakes as an emerging topic of concern.

A set of three presentations and discussions, “” will take place on Saturday, Feb. 15, at the Washington State Convention Center.

Organized by , an assistant professor of Earth and space sciences at the UW, and , a 91̽��professor of Earth and space sciences and director of the UW-based , the event will provide the latest research on seismic hazards, both along the coast and in built-up areas inland.

“We hope to inform the audience and public about what is and is not known about subduction-zone earthquakes and their effects,” Tobin said. “While the scenarios will be specific to Cascadia, the fundamental work is about investigating how fault movement launches tsunamis and under what conditions the seismic waves create ground shaking that affects buildings and other structures.”

The title references a line from the infamous 2015 New Yorker article, “,” that put Pacific Northwest megaquakes on the popular radar. Evidence from tsunamis shows that a huge earthquake occurred off the Pacific Northwest on January 26, 1700. The U.S. Geological Survey estimates a 14% chance it could occur again in the next 50 years.

The session will consider both what such an earthquake might look like, and what it could mean for buildings and other structures in Seattle — many of which were built before the region’s seismic hazards were fully understood.

, director of the Center for Tsunami Research at the National Oceanic and Atmospheric Administration, will begin the session at 3:30 p.m. with a discussion of , which is the greatest hazard to communities on the Washington and Oregon coasts. Then, , a research geophysicist at the U.S. Geological Survey and 91̽��affiliate assistant professor in Earth and space sciences, will present on .

Wirth builds on her 2017 work, as a 91̽��postdoctoral researcher, that simulated what a magnitude-9 megathrust earthquake could look like depending on where along the Cascadia subduction zone the offshore rupture starts, and how close the slipping gets to cities on land. The team has now refined its results and begun to apply the simulations to estimate infrastructure damage.

“Since we don’t have any direct observational records of the 1700 earthquake, our 3D supercomputer simulations of various possible magnitude-9 Cascadia earthquake scenarios has allowed us to quantify the range of possible ground shaking the Pacific Northwest might experience,” Wirth said.

, a 91̽��professor of civil and environmental engineering, will close with a talk focused on damage, titled: “.” He is leading the research on building response with , a 91̽��professor of civil and environmental engineering.

On Saturday, Berman will share results of a published this month in the Journal of Structural Engineering that considers how 32 midrise to tall building types, ranging from 4 to 40 stories, would fare in 30 different simulated Cascadia magnitude-9 earthquakes. The study led by , a 91̽��postdoctoral researcher, finds that the current building codes underestimate how much shaking would occur as the loose soil in the Seattle basin amplifies the frequency of waves generated by offshore earthquakes, with strong shaking projected to last for almost two minutes.

“The Cascadia subduction zone ground motions have longer duration and different frequency content than the ground motions experienced in California, which has formed the basis for most U.S. building codes,” Berman said. “The impact of those differences on structural performance was a big unknown prior to this research.”

Each presentation will also include questions from those attending the AAAS annual meeting.

“We are hoping that our session communicates the latest in subduction-zone research, but we also look forward to opening up a dialog between panelists and the audience,” Duvall said. “The AAAS format is special that way, that it offers a real chance for two-way communication.”

, a 91̽��assistant professor of Earth and space sciences, was selected for the Luna B. Leopold Award for early career scientists. The award recognizes scientists within five years of receiving their doctorate who have made “a significant and outstanding contribution that advances the field of Earth and planetary surface processes.”

The honor is named after Luna Leopold, an American geomorphologist and hydrologist and son of author and conservationist Aldo Leopold. Duvall will accept the honor and deliver the Robert Sharp Lecture in December at the union’s annual fall meeting in San Francisco.

Duvall earned her doctorate at the University of Michigan in 2011 and completed a postdoctoral fellowship at the University of Colorado before joining the 91̽��faculty in 2012. She led a recent study that used a new technique to establish the long-term around the site of the deadly March 2014 landslide in Oso, Washington.

In the nomination package, 91̽��professor David Montgomery wrote to support Duvall for her “contributions to fluvial, hillslope, and tectonic geomorphology that have fundamentally advanced understanding of landscape dynamics across a wide range of scales.”

At the same fall meeting of the American Geophysical Union, two other 91̽��faculty members will also deliver invited talks. , professor and director of the 91̽��School of Oceanography, will deliver the in the Ocean Sciences section. , a 91̽��professor of atmospheric sciences, will deliver the in the focus group on Global Environmental Change.

All three lectures will be streamed live online in December and will be recorded for later viewing. See a full list of on the American Geophysical Union’s website.

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“,” by 91̽��alumnus , lines the walls with 6,000 unique backlit panels inspired by the geology of the site that was excavated to create the station.

91̽��geologist , a 91̽��assistant professor of Earth and space sciences, provided an accompanying narration. She met with a Sound Transit employee in January and talked about her research, the history of the station site, and her impressions of the station’s geology-themed art installation.

“It stretches from the ceiling all the way down, so as you go down the escalator it captures what it’s like going into the deeper geologic units,” Duvall said.

The narration played March 19 during opening day, when riders had their first opportunity to travel down to the station and on the new rail line. You can play the 15-minute clip yourself as you walk through the station:

“If you went to most places on Earth, the geology wouldn’t be very complex in such a small little footprint,” Duvall said. “But what’s exciting about our area is that, because of the ice cap coming in and out and depositing all these different materials, we get diversity and nonconformity in just a small window. So there’s quite a lot happening there.”

Duvall saw evidence in the soil cores from the station site of at least two ice sheets from British Columbia advancing and retreating and leaving different materials in their wake. Studies show that the Pacific Northwest has experienced six or seven glacial-interglacial cycles.

“I think the artist did a really good job of capturing the nonconformity and complexity of where one geologic unit stops and another starts,” Duvall said. “This is very different from the traditional geological layer cake, like you would see in the Grand Canyon.”

She was interested that Berk’s piece includes some common geologic symbols, such as small dots for finer sediment and open circles for large cobbles, but that he invented some of his own, such as the horseshoes that appear on some panels.

The station is now providing travel options that some predict could . Many people hope this new connection to the 91̽��will shorten commutes and relieve traffic congestion. For her part, Duvall hopes it prompts new appreciation for what lies beneath.

“I hope that riders will stop and think: ‘Wait a minute, yeah, there is a whole record under the Earth’s surface that is an archive of all these things that have happened in the past, ‘” Duvall said. “And hopefully they will learn a little something about the place they live.”

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For more information, contact Duvall at 206-221-8311 or aduvall@uw.edu.

91̽�� geologists analyzed woody debris buried in earlier slides and used radiocarbon dating to map the history of activity at the site. The , published online Dec. 22 in the journal , show that a massive nearby slide happened around 500 years ago, and not thousands of years ago as some had believed.

“The soil in this area is all glacial material, so one hypothesis is the material could have fallen apart in a series of large landslides soon after the ice retreated, thousands of years ago,” said corresponding author , a 91̽��doctoral student in Earth and space sciences. “We found that that’s not the case — in fact, landslides have been continuing in recent history.”

The study establishes a new method to date all the previous landslides at a particular location. The method shows that the slopes in the area around Oso have collapsed on average once every 500 years, and at a higher rate of about once every 140 years over the past 2,000 years.

“This was well known as an area of hillslope instability, but the question was: ‘Were the larger slides thousands of years old, or hundreds of years old?’ Now we can say that many of them are hundreds of years old,” said co-author , a 91̽��assistant professor of Earth and space sciences.

LaHusen had not yet begun his graduate studies when he asked about studying the history of geologic activity at the Oso site. In late summer of 2014, the researchers began their work wading along riverbanks to look for preserved branches or trees that could be used to date previous landslides.

“When you have a large, catastrophic landslide, it can often uproot living trees which kills them and also encapsulates them in the landslide mass,” Duvall said. “If you can find them in the landslide mass, you can assume that they were killed by the landslide, and thus you can date when the landslide occurred.”

The team managed to unearth samples of wood buried in the Rowan landslide, just downstream of the Oso site, and the Headache Creek landslide, just upriver of the 2014 slide. Results from several debris samples show that the Rowan landslide, approximately five times the size of the Oso slide, took place just 300 to 694 years ago. The Headache Creek landslide is within a couple hundred years of 6,000 years old.

Previous 91̽�� had shown a history of geologic activity at the Oso site, including previous major landslides and a recent small slide at the same slope that collapsed in 2014. But while the position of past slides and degree of surface erosion can show the order that the older slides happened, it has not been possible to give a date for the past events.

The new study uses the radiocarbon dates for two slides to establish a roughness curve to date other events along a 3.7-mile (6-kilometer) stretch of the north fork of the Stillaguamish River. A roughness curve uses the amount of surface erosion to establish each slide’s age. The two dates put firm limits on the curve, so that other nearby slides can be dated from their roughness characteristics without having to find material buried inside each mass of soil.

“This is the first time this calibrated surface dating method has been used for landslide chronologies, and it seems to work really well,” LaHusen said. “It can provide some information about how often these events recur, which is the first step toward a regional risk analysis.”

Applying the new method for other locations would require gathering samples for each area, they cautioned, because each site has its own soil composition and erosion characteristics.

It’s not known whether the findings for the Oso site’s history would apply to other parts of the Stillaguamish River, Duvall said, or to other places in Washington state. The researchers are still studying debris from other locations. But the results do have implications for the immediate area.

“It suggests that the Oso landslide was not so much of an anomaly,” Duvall said.

She and LaHusen are also working with the UW’s , which is studying hazards from magnitude-9 earthquakes along the Cascadia subduction zone. They would like to learn whether landslides across Washington state coincided with past earthquakes, and use simulations of future shaking to predict which places in the state are most vulnerable to earthquake-triggered landslides.

Other co-authors on the new paper are at the 91̽��and at Portland State University. The study was funded by the National Science Foundation, the Geological Society of America, and the UW’s Quaternary Research Center.

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For more information, contact Duvall at 650-815-5560 or aduvall@uw.edu and LaHusen at seanlah7@uw.edu. Note: Duvall and LaHusen are currently out of town and best reached via email. Duvall is on the East Coast and will be on campus Sunday, Dec. 27, and then doing fieldwork in New Zealand from Dec. 28 to Jan. 16. LaHusen will be back on campus Jan. 4.

More photos are posted at .

NSF grant: EAR-1331412