The Cascadia Subduction Zone is unusually quiet for a megathrust fault. Spanning more than 600 miles from Canada to California, the fault marks the convergence of the Juan de Fuca and North American plates. While other subduction zones produce sporadic rumblings as the plates scrape past each other, Cascadia , fueling assumptions that the plates are locked together by friction.

The subduction zone 鈥� miles offshore and deep underwater 鈥� is difficult to observe. Most data collection is based onshore, which limits the breadth and quality of results. The lack of earthquakes further complicates efforts to understand its behavior and structure.

In a new study, the first to monitor strain offshore for an extended period of time, 天美影视传媒 researchers report that the plates may not be fully locked. Based on 13 years of ground motion data from sensors in different regions, the study shows the northern portion of the fault is locked and quiet, but the central region appears to be more active. There, researchers observed signs of a shallow, slow-motion earthquake and detected pulses of fluid flowing through subterranean channels, which may relieve pressure from the fault.

The findings, , may alter expectations of how this area will respond to a large earthquake. Similar features in other places have stopped a rupture that might have otherwise continued along the entire fault line.

鈥淚t鈥檚 preliminary, but we think that variable fluid pathways in Cascadia will change the behavior of large earthquakes on the fault,鈥� said co-author , a UW associate professor of Earth and space science.

The Juan de Fuca plate is advancing toward the North American plate at a rate of . But because the plates are stuck together, that motion generates pressure. Eventually, the building tension will exceed what the plates can tolerate. When they eventually slip free, an earthquake will spread along the boundary.

Megathrust earthquakes, which occur at boundaries where one plate slides beneath another, rock the Pacific Northwest every 500 or so years. one to 1700, and estimates suggest a 10 to 15% chance that the entire fault will rupture, producing an earthquake that could exceed magnitude 9, within the next fifty years. The results from this study do not alter those odds, but the dynamics captured might influence the severity of the eventual earthquake.

A recent survey of the seafloor found that into at least four geologically distinct segments. Each one may be insulated from a rupture in another region. In this study, the researchers took a closer look at two of the regions by analyzing data from three monitoring stations, one near Vancouver Island and two off the coast of Oregon.

鈥淲e wanted to understand strain changes in different regions offshore,鈥� said lead author , a UW doctoral student of oceanography. 鈥淲e used the seismometers to measure how the seismic velocity varies underneath each station.鈥�

Seismic velocity is a term used to describe the rate at which ambient noise travels through a material. Because the speed of sound depends on what it is moving through, tracking seismic velocity can give researchers a window into processes occurring beneath the ocean floor.

鈥淲hen you compact something, you can expect the sound waves to move through it faster,鈥� said Kidiwela.

The steady increase in seismic velocity observed at the northern site told the researchers the rock was compacting, which supports the theory that the two plates are locked in place.

The central region displayed a different pattern. For two months in 2016, seismic velocity decreased. The researchers attribute this drop to a slow-motion earthquake on the shallow edge of the oceanic plate that relieved some of the pressure at the fault.

Other drops in seismic velocity, recorded between 2017 and 2022, were linked to fluid dynamics. Subduction squeezes liquid out of rocks and pushes it toward the surface. The study found that other faults, running perpendicular to the subduction zone, may act as pathways for letting trapped fluid out.

鈥淒uring a megathrust rupture, one of the ways that an earthquake propagates is through fluid pressure. If you have a way to release these fluids, it could help improve the stability of the fault, and potentially impact how the region behaves during a large earthquake,鈥� Kidiwela said.

Pulling data from just three sites, the researchers observed complex dynamics that may have gone overlooked. Future work will greatly expand this effort. in 2023 to build an underwater observatory in the Cascadia Subduction Zone.

鈥淔inding this link between fluids coming to the shallow subduction zone is pretty unique, as is the evidence that the fault is not completely locked,鈥� said co-author , a UW professor of oceanography and one of the scientists involved with the observatory. 鈥淚t suggests that we need more instruments there, because there may be more going on than people have been able to figure out before.鈥�

Additional co-authors include from the University of Utah.聽

This study was funded by the Jerome M. Paros Endowed Chair in Sensor Networks at the 天美影视传媒 and the National Science Foundation.聽

For more information, contact Kidiwela at seismic@uw.edu.

Leveraging the tectonic laboratory of the Cascadia subduction zone, the 天美影视传媒 today announced a new effort to best understand how to study and live with the threats of earthquakes, tsunamis, volcanos, landslides and other seismic hazards. Dubbed the GeoHazards Initiative, the interdisciplinary work aims to develop and promote the adoption of early detection systems both on land and at sea to help prevent the loss of human life and property.

鈥淭he vision ultimately is for an integrated initiative that will span geohazards and their impact on society,鈥� said , the newly named Paros Endowed Chair in Seismology and Geohazards. 鈥淎 big goal of this new effort is to bring together the strengths of different pieces of the UW research community to tackle all these problems in a truly novel way that can help us make progress on understanding all of those hazardous events and how to mitigate their damaging effects.鈥�

The initiative鈥檚 starting place will be focused on sensors, both on land and at sea, that can help scientists better understand seismic events and how to detect them as they begin, and even to determine times and places where risk may be heightened.

鈥淲e need to be able to detect movement deep beneath the ground both on land and under the ocean equally, in order to take this to the next level,鈥� Tobin said, who already is the Washington state seismologist, directs the , and is a professor in the Department of Earth & Space Sciences. 鈥淎nd that’s traditionally been two different realms here at the university. But really it鈥檚 all an Earth process and we need to work together.鈥�

Tobin will initially partner with researchers in the UW School of Oceanography and the UW Applied Physics Lab, with hopes to bring other parts of the university in as the research progresses.

The work is fueled by a $2 million gift from Jerome 鈥淛erry鈥� M. Paros to fund the named chair. Additionally, UW will match that gift with $2 million to be used over 20 years to launch and support the initiative.

鈥淭he UW is uniquely positioned to be a leader in understanding how geohazards impact our lives,鈥� said Paros, a leader in the field of geophysical measurements. He is the founder, president and chairman of Paroscientific, Inc., Quartz Seismic Sensors, Inc. and related companies that use the quartz crystal resonator technology he developed to measure pressure, acceleration, temperature, weight and other parameters. 鈥淲e just now are beginning to have better detection systems on land and at sea. This effort knits these resources together under Harold鈥檚 direction. We couldn鈥檛 be better positioned to push this work forward, ideally protecting property and saving lives.鈥�

Paros has supported science and education with philanthropic endowments at universities and organizations across the country. His prior contributions to the UW include the endowment of the Jerome M. Paros Chair in Sensor Networks and the Cascade Sensor Network Fund. These gifts support the research, development and deployment of new instrumentation and measurement systems that will advance cross-disciplinary knowledge in the oceanic, atmospheric and Earth sciences. In addition, Paros established the Paros Fund for Brain Research at the Institute for Learning & Brain Sciences.

With the Paros Endowed Chair in Seismology and Geohazards, Tobin now has a platform from which to launch the development of new sensing systems on land and under the sea, build coalitions of public and private stakeholders in the Pacific Northwest and beyond, and engage policymakers at the state and federal levels.

The initiative will launch new research to design, build and deploy arrays of ocean sensors to detect earthquakes, tsunamis and seafloor motion, and to provide data transmission that connects onshore and offshore observations to effectively detect emerging geohazards and mitigate against disasters.

Technological options for the array could include sensors connected to cables on the seafloor, attached to both dedicated research cables and existing commercial telecom cables. Arrays could also include offshore boreholes, standalone stations on the seafloor that store their data, and mobile platforms like drones or buoys.

鈥淥ffshore sensors can help provide early warning for earthquakes and tsunamis, and help advance scientific understanding of what鈥檚 happening under the ocean in the Cascadia subduction zone,鈥� said , the Jerome M. Paros聽Endowed Chair in聽Sensor Networks and professor in the School of Oceanography, who will also work on the GeoHazards Initiative.

鈥淲e already have systems on land that can provide early warnings of seismic events, but we now are developing technologies that can help us better understand earthquakes under the ocean and the tsunamis they produce,鈥� Wilcock said.

The researchers said they plan to investigate the fault systems onshore and offshore using geophysical imaging and direct measurements for groundtruthing to gain insight into the geohazard sources and processes.

鈥淭hese activities will build a strategic alliance across the university to position UW as the foremost hub of subduction hazard research, positioning us to compete for emerging national and international opportunities,鈥� Tobin said.

He said it was an honor to receive this new endowed chair in Paros鈥� name, a man who has personally been a driving force in the development of geophysical sensors that are in use across the world.

鈥淚 feel a responsibility to really make this initiative be effective and serve as a platform to work on these problems at a larger scale,鈥� Tobin said. 鈥淲e in Western Washington literally inhabit the subduction zone 鈥� the place where two plates meet 鈥� that is this perfect place to study all these processes from within them. And the 天美影视传媒 has the kind of critical mass of expertise and people, and the forward-looking science and technology, to really take concrete steps to leap forward our understanding not just for Washington but for the world.鈥�

For more information, reach Tobin at htobin@uw.edu.

天美影视传媒 oceanographers are working with a local company to develop a simple new technique that could track seafloor movement in earthquake-prone coastal areas. Researchers began testing the approach this summer in central California, and they plan to present initial results in December at the American Geophysical Union’s annual meeting in New Orleans.

Their approach uses existing water-pressure sensors to cheaply measure gradual swelling of the seafloor over months to years. If successful, the innovative hack could provide new insight into motion along the Cascadia Subduction Zone and similar faults off Mexico, Chile and Japan. The data could provide clues about what types of earthquakes and tsunamis each fault can generate, where and how often.

The concept began with a workshop in 2012 that brought together , the founder of Bellevue-based Paroscientific, Inc., with UW geoscientists. Paros’ company manufactures sensors used to measure pressure at the bottom of the ocean with high precision, which are used by the National Oceanographic and Atmospheric Administration for its tsunami sensors.

But an engineering quirk prevents the sensors from measuring the gradual ground motions that build up pressure along earthquake faults. The instruments can measure seafloor pressure, or the weight of water above the sensor, to an extremely precise fraction of a millimeter. But the readings lose accuracy over time, and the error is proportional to the quantity measured. On the ocean floor, where pressures are tens to hundreds of times that on the surface, the readings can change by 10 centimeters (3 inches) per year. In between major earthquakes, this is much more than the seafloor might shift up or down due to tectonic forces.

“If you want to measure how the seafloor is moving, you don’t want your reading to change by a larger value than the thing that you’re measuring,” said , an engineer at the UW’s Applied Physics Laboratory who is working on the project.

Paros proposed an idea that would instead calibrate the pressure sensor against the air pressure inside the metal case that houses the instrument, which is roughly one atmosphere. This would allow existing pressure sensors to autonomously track small bulges and slumps on the seafloor.

Last year engineers at the UW Applied Physics Laboratory modified an existing Paros pressure sensor. The sensitive quartz crystal that measures the seafloor pressure can now be connected to measure pressure inside its titanium instrument case, with a known pressure and another barometer to check the value. The prototype instrument was attached in mid-June to the , a cabled seafloor observatory that lets researchers communicate directly with the instrument.

“That chunk of seafloor actually does not move much. We’re looking for a null result,” Manalang said. “If successful, the next step would be to deploy similar instruments in some more geologically active areas.”

Those areas include the Cascadia Subduction Zone, the fault that could unleash the at any time on the Pacific Northwest. Geologists studying the small rise and fall of this section of seafloor, around 1 centimeter per year, have instead been forced to develop complicated workarounds.

“We are trying to find a pattern of which areas are going up and which areas are going down, and how quickly, which can potentially tell us where the subduction zone fault is locked,” said , a UW oceanography professor who holds the Paros endowed chair. “But we can’t yet do that with a conventional pressure sensor.”

Wilcock and seismologists at Scripps Institution of Oceanography have been monitoring seafloor movement off central Oregon, where the Cascadia Fault displays behavior that suggests it may gradually slip, releasing strain along that section of the fault. Once a year, the partners go to sea with a research ship, deep-sea robot and specialized equipment to calibrate six seafloor pressure sensors. By monitoring exactly how the seafloor has moved in this way from one summer to the next, they can compare sections of the fault and learn which zones are fully locked, building up potentially dangerous energy, and which aren’t.

“The approach we are using appears to work, but it’s expensive, and you can’t do it very often,” Wilcock said.

If Paros’ modified sensors can do the job, future work might place a network of them along Cascadia or other subduction zones, in which a seafloor plate plunges beneath a continental plate. Measuring motion along different parts of these faults might answer longstanding questions about how and where a fault ruptures.

From her Seattle office, Manalang now communicates with the prototype sensor in Monterey and flips the crystal about once each weekday to recalibrate it against the instrument housing pressure. She will flip it less often as the test continues, while remotely monitoring the change in pressure readings.

“We’re still close to the starting line on this one, and have some initial, really promising results,” Manalang said. Observations so far show that the shift in measurements is predictable, and similar at both ends of the instrument’s range. “We’re at the very beginning of what we hope is a fairly long-term test,” she said.

If the method proves reliable, future pressure sensors could be programmed to pivot periodically on their own and gather observations over months or years. Precise long-term measurements of water pressure could not only help seismologists, but also researchers who study how sea level changes over decades.

“If you can make very accurate observations, and routinely, it would interest both the people studying what’s happening beneath and what’s happening above,” Wilcock said. “These data would open up a whole bunch of new studies.”

The research is funded by Jerry Paros and the 天美影视传媒.

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For more information, contact Wilcock at 206-543-6043 or wilcock@uw.edu and Manalang at 206-685-9910 or manalang@uw.edu.

“The new network allowed us to see in incredible detail where the faults are, and which were active during the eruption,” said lead author , a UW professor of oceanography. The in Science is one of three studies published together that provide the first formal analyses of the seismic vibrations, seafloor movements and rock created during an off the Oregon coast. “We have a new understanding of the behavior of caldera dynamics that can be applied to other volcanoes all over the world.”

The studies are based on data collected by the , a National Science Foundation-funded project conceived and implemented by 天美影视传媒 scientists and engineers that brings electrical power and internet to the seafloor. The observatory, completed just months before the eruption, provides new tools to understand one of the test sites for understanding Earth’s volcanism.

“Axial volcano has had at least three eruptions, that we know of, over the past 20 years,” said , director of the NSF’s Division of Ocean Sciences, which also funded the research.聽 “Instruments used by Ocean Observatories Initiative scientists are giving us new opportunities to understand the inner workings of this volcano, and of the mechanisms that trigger volcanic eruptions in many environments.

“The information will help us predict the behavior of active volcanoes around the globe,” Murray said.

It’s a little-known fact that most of Earth’s volcanism takes place underwater. Axial Volcano rises 0.7 miles off the seafloor some 300 miles off the Pacific Northwest coast, and its peak lies about 0.85 miles below the ocean’s surface. Just as on land, we learn about ocean volcanoes by studying vibrations to see what is happening deep inside as plates separate and magma rushes up to form new crust.

The submarine location has some advantages. Typical ocean crust is just 4 miles (6 km) thick, roughly five times thinner than the crust that lies below land-based volcanoes. The magma chamber is not buried as deeply, and the hard rock of ocean crust generates crisper seismic images.

“One of the advantages we have with seafloor volcanoes is we really know very well where the magma chamber is,” Wilcock said. “The challenge in the oceans has always been to get good observations of the eruption itself.”

All that changed when the Cabled Array was installed and instruments were turned on. Analysis of vibrations leading up to and during the event show an increasing number of small earthquakes, up to thousands a day, in the previous months. The vibrations also show strong tidal triggering, with six times as many earthquakes during low tides as high tides while the volcano approached its eruption.

Once lava emerged, movement began along a newly formed crack, or dike, that sloped downward and outward inside the 2-mile-wide by 5-mile-long caldera.

“There has been a longstanding debate among volcanologists about the orientation of ring faults beneath calderas: Do they slope toward or away from the center of the caldera?” Wilcock said. “We were able to detect small earthquakes and locate them very accurately, and see that they were active while the volcano was inflating.”

The two previous eruptions sent lava south of the volcano’s rectangular crater. This eruption produced lava to the north. The seismic analysis shows that before the eruption, the movement was on the outward-dipping ring fault. Then a new crack formed, initially along the same outward-dipping fault below the eastern wall of the caldera. The outward-sloping fault has been predicted by so-called “sandbox models,” but these are the most detailed observations to confirm that they happen in nature. That crack moved southward along this plane until it hit the northern limit of the previous 2011 eruption.

“In areas that have recently erupted, the stress has been relieved,” Wilcock said. “So the crack stopped going south and then it started going north.” Seismic evidence shows the crack went north along the eastern edge of the caldera, then lava pierced the crust’s surface and erupted inside and then outside the caldera’s northeastern edge.

The dike, or crack, then stepped to the west and followed a line north of the caldera to about 9 miles (15 km) north of the volcano, with thousands of small explosions on the way.

“At the northern end there were two big eruptions and those lasted nearly a month, based on when the explosions were happening and when the magma chamber was deflating,” Wilcock said.

The activity continued throughout May, then lava stopped flowing and the seismic vibrations shut off. Within a month afterward the earthquakes dropped to just 20 per day.

The volcano has not yet started to produce more earthquakes as it gradually rebuilds toward another eruption, which typically happen every decade or so. The observatory centered on Axial Volcano is designed to operate for at least 25 years.

“The cabled array offers new opportunities to study volcanism and really learn how these systems work,” Wilcock said. “This is just the beginning.”

Other co-authors of the paper are UW oceanography doctoral student ; Maya Tolstoy, Felix Waldhauser and Yen Joe Tan at Columbia University; DelWayne Bohnenstiehl and M. Everett Mann at North Carolina State University; Jacqueline Caplan-Auerbach at Western Washington University; Robert Dziak at the National Oceanic and Atmospheric Administration; and Adrien Arnulf at the University of Texas at Austin.

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For more information, contact Wilcock at 206-543-6043 or wilcock@uw.edu.

Note to media: Images are at . Video is at聽 and

A carcass that washed up on a Seattle-area beach this spring provided a reminder that sleek fin whales, nicknamed “greyhounds of the sea,” are vulnerable to collision when they strike fast-moving ships. Knowing their swimming behaviors could help vessels avoid the animals. Understanding where and what they eat could also help support the fin whale’s slowly rebounding populations.

天美影视传媒 oceanographers are addressing such questions using a growing number of seafloor seismometers, devices that record vibrations. A series of three papers published this winter in the interprets whale calls found in earthquake sensor data, an inexpensive and non-invasive way to monitor the whales. The studies are the first to match whale calls with fine-scale swimming behavior, providing new hints at the animals’ movement and communication patterns.

The research began a decade ago as a project to monitor tremors on the Juan de Fuca Ridge, a seismically active zone more than a mile deep off the Washington coast. That was the first time UW researchers had collected an entire year’s worth of seafloor seismic data.

“Over the winter months we recorded a lot of earthquakes, but we also had an awful lot of fin-whale calls,” said principal investigator , a UW professor of oceanography. At first the fin whale calls, which at 17 to 35 vibrations per second overlap with the seismic data, “were kind of just a nuisance,” he said.

In 2008 Wilcock got funding from the Office of Naval Research to study the previously discarded whale calls.

, a UW doctoral student in oceanography, compared the calls recorded by eight different seismometers. Previous studies have done this for just two or three animals at a time, but the UW group automated the work to analyze more than 300,000 whale calls.

The method is similar to how a smartphone’s GPS measures a person’s location by comparing paths to different satellites. Researchers looked at the fin whale’s call at the eight seismometers to calculate a position. That technique let them follow the animal’s path through the instrument grid and within 10 miles of its boundaries.

Soule created 154 individual fin whale paths and discovered three categories of vocalizing whales that swam south in winter and early spring of 2003. He also found a category of rogue whales that traveled north in the early fall, moving faster than the other groups while emitting a slightly higher-pitched call.

https://soundcloud.com/uw-today/finwhale-and-earthquake

“One idea is that these are juvenile males that don’t have any reason to head south for the breeding season,” Soule said. “We can’t say for sure because so little is known about fin whales. To give you an idea, people don’t even know how or why they make their sound.”