Portland State researchers hope project will reduce mega earthquake damage
The researchers are working on a soil treatment that focuses on activating microbes to reduce groundwater saturation levels – they believe it could become a cost-effective, long-lasting solution to reduce earthquake-caused liquefaction.
If and when a Cascadia Subduction Zone earthquake hits the Portland region, soil liquefaction could dramatically worsen the damage, leading buildings to tilt, roads to buckle and utility lines to rupture. Especially susceptible are sandy and silty soils – like those by the Willamette River where aging tanks store fuels including gasoline, diesel and biofuel. Intense shaking during an earthquake could cause those soils to behave more like a liquid than a solid, leading the tanks to crack, collapse, spill and explode. But Portland State University researchers say soil microbes could help prevent the destruction. The researchers are working on a soil treatment that focuses on activating microbes to reduce groundwater saturation levels – and they believe it could become a cost-effective, long-lasting solution to reduce earthquake risk in their own city and across the region. “We recognized that it would be an opportunity to test it in Portland to see if it could be applied in areas like the CEI Hub,” said Diane Moug, one of the lead researchers of the PSU microbial treatment study and an assistant professor of civil and environmental engineering at the school.The treatment is one of several new soil-based solutions being developed to prevent or reduce liquefaction – but, unlike traditional soil improvement methods, the microbe technique is based in nature and doesn’t entail invasive procedures such as injecting cement into the ground or repeatedly dropping large weights to compact the soil, said Ellen Rathje, a professor of geotechnical engineering at the University of Texas at Austin. “This area of research is a very hot topic right now,” said Rathje, who is also president of the Earthquake Engineering Research Institute, a nonprofit for experts working to reduce earthquake risks. “There’s promise in the bio-inspired techniques because there are very limited approaches you can use for sites that have already been developed. And they’re inspired by naturally occurring processes, so they’re certainly good from a sustainability perspective.”Dubbed microbially induced desaturation, the method being tested by PSU entails injecting the layers of soil that lie beneath the surface with a mixture containing calcium acetate and calcium nitrate. And then waiting. The mixture acts as a food source for naturally occurring soil microbes, stimulating their growth, said Arash Khosravifar, the co-leader of the PSU project and an associate professor of civil and environmental engineering at the school.The microbes produce large amounts of nitrogen gas and carbon dioxide – a chemical reaction called denitrification. Those nitrogen gas bubbles, in turn, fill the tiny spaces between soil particles, reducing the soil’s saturation and making it more resistant to liquefaction, Khosravifar said. In the event of an earthquake, the trapped gas bubbles act like shock absorbers, dampening water pressure buildup in the soil during intense shaking, he said. Scientists believe Oregon is overdue for the Big One, a mega earthquake that will occur just off the Oregon coast along the Cascadia Subduction Zone where the Juan de Fuca Plate pushes beneath the North American Plate – and its shaking will devastate Portland. The last major Cascadia Subduction Zone quake happened in 1700 and there’s about a 37% chance that one of 7.1 magnitude or larger will occur in the next 50 years, according to the Oregon Department of Emergency Management. The state and city of Portland have mapped liquefaction risks, finding they’re among the highest along the Columbia and Willamette rivers, including the Critical Energy Infrastructure Hub where hundreds of fuel-filled tanks sit atop a six-mile stretch of unstable soils. Three years ago, following years of research and community pressure over the earthquake-related risks of spills and explosions at the hub, the Legislature mandated that tank owners develop plans to reduce seismic risks. “The state set a very high standard of seismic resilience, but they don’t dictate how a facility has to reach that. Soil-based solutions could be one of many options for these companies,” said John Wasiutynski, sustainability director with Multnomah County, which in 2022 published a study showing a liquefaction-related spill at the Portland hub would be similar to the BP Deepwater Horizon oil spill disaster in the Gulf of Mexico, the country’s largest oil spill to date.Inspired by the study, Portland researchers learned about the microbial method from colleagues at Arizona State University. Other researchers have also launched similar field work, including in Japan and Italy. From lab to fieldLab tests, which use small soil samples and mechanical shakers to simulate earthquakes, have shown that stimulating the growth of microbes and reducing soil saturation even by a few percentage points can significantly reduce liquefaction, Portland researchers said. Khosravifar, Moug and their collaborators are now aiming to prove the method can eliminate liquefaction in the real world, where soil conditions and scale are more complex – as is stimulating earthquakes. Enter the T-Rex, a massive truck outfitted with a mobile shaker that makes artificial earthquakes. The truck, which Portland researchers borrowed from the University of Texas at Austin, got its name from a scene in “Jurassic Park” where the pounding steps of a Tyrannosaurus rex create ripples in a water glass. The T-Rex truck pounds the ground and causes it to shake. The T-rex, a field shaker truck borrowed from the University of Texas at Austin, produces a small earthquake by shaking the ground. In September 2025, Portland State University researchers simulated earthquakes in the field to see if their microbe-focused soil treatment method can prevent the soil liquefying during a mega earthquake.courtesy of Portland State UniversityIn 2019, researchers conducted initial field tests at two sites, one in Northeast Portland near the Columbia River and another in Northwest Portland near the energy hub on the Willamette. They successfully pumped the treatment into fine-grained silt soils at the sites and showed that it desaturated the soils, according to a paper published in 2022 in the Journal of Geotechnical and Geoenvironmental Engineering.They have monitored the Northeast Portland site for six years and have found the treatment is effective for up to five years, Khosravifar said. Throughout August, they retreated the soil at the site, applying the solution to the subsurface soil through a central injection well. Two weeks ago, they installed a giant screw into the ground. The T-rex sat on top of the screw and shook the pile vertically, transferring the shaking energy down into the soil. What they found: The T-rex generated an earthquake – but while mighty, it wasn’t strong enough in deeper soil, Khosravifar said. The researchers are now working on how to increase the shaking intensity, he said, up to a point where the shaking will at least partially liquify the untreated soil and researchers can see the impacts of the treatment in areas injected with the chemicals. “One of the things that remains to be answered is, how much can we really mitigate liquefaction risk? Are we completely eliminating that risk or is it partial?” Khosravifar said. Challenges, drawbacksThe treatment comes with some risks. While the chemicals are benign to humans – calcium nitrate is widely applied to crops as a fertilizer and calcium acetate is a food-grade material used as a preservative in foods and a binder in pharmaceutical pills – the denitrification process, if incomplete, can leave behind nitrates or intermediate compounds like nitrite, nitric oxide or nitrous oxide, Khosravifar said. Nitrous oxide is a potent greenhouse gas. And nitrates or its compounds can contaminate drinking water. Research has linked high nitrate consumption over long periods to cancers, miscarriages and thyroid issues. It is especially dangerous to infants who can develop “blue baby syndrome,” which can be fatal. The formation of gas bubbles in the soil also can reduce porosity and conductivity of soil, potentially affecting water flow. It’s why the soil treatment requires specialized instruments to closely monitor the chemical reaction and nitrate and nitrite levels in groundwater, Khosravifar said. Sensors are embedded in the soil down to 20 feet to give researchers an idea of how the nutrients are moving in soil and whether the chemical reaction is complete. If the method is widely adopted, contractors performing the treatment would be required to use such sensors for long-term monitoring, he said. Other methodsStill, the microbe stimulation method could be a better option when compared to other soil treatments, the researchers said. Some entail injecting bacteria into soil rather than working with existing ones. One of the methods often uses urea, which produces ammonia, a toxic chemical that can damage water quality and is hard to remove.A more established soil improvement approach, known as permeating grouting, calls for injecting microfine cement into the cracks and fissures in liquefaction-prone soils – but it’s emission-intensive, uses a lot of water and is a lot more expensive. Mechanical compaction, another widely used soil treatment method, involves physically packing the soil down tightly so it’s stronger and less likely to shift or collapse during an earthquake.Portland General Electric, for example, used a method that mixed cement into the soil to create stiff, strong columns underground across the Harborton Substation, a major electrical substation in Northwest Portland just west of the energy hub. The project was completed during a rebuild of the substation in 2020 to address soils prone to liquefaction and cost about $40 million, said PGE spokesperson Amber Weyers. The main challenge with such methods is that they require access to the soil. For soils with existing structures or buildings – such as those under the fuel-filled tanks at Critical Energy Infrastructure Hub by the Willamette – there is no good solution. In those cases, PSU’s microbially induced desaturation method may prove the only one feasible, the researchers said.It’s also about a quarter of the cost of many of the other liquefaction prevention solutions, Khosravifar said. For areas occupied by a fuel tank, for example, the nitrate treatment’s initial application would cost $170,000, including the cost of installing wells, he said. Though the chemicals would have to be reapplied every five years, subsequent applications would cost a fifth of the initial expense or about $34,000 every five years, Khosravifar said. Still, the soil treatment is unlikely to be used by homeowners, given that over time it would cost a lot more than the house itself, Khosravifar said. That’s still a fraction of the cost for permeating grouting, which can cost five times as much, or more than $600,000, he said. Moug and Khosravifar said they would like to collaborate with one of the fuel storage companies housed at the Portland energy hub to test and monitor another patch of soil – to better understand how soil and water behave at the hub itself. “We’re not ready to fully implement this solution yet, but it would be a logical next step to test it on site,” Moug said. If you purchase a product or register for an account through a link on our site, we may receive compensation. By using this site, you consent to our User Agreement and agree that your clicks, interactions, and personal information may be collected, recorded, and/or stored by us and social media and other third-party partners in accordance with our Privacy Policy.
