The Cascadia Subduction Zone, which runs along the North American west coast from Northern California to British Columbia, Canada, is capable of generating large earthquakes. But the region’s seismic hazards are not well understood. A new research center will study the region and increase preparedness.
The Cascadia Region Earthquake Science Center (CRESCENT) will include researchers from 14 U.S. institutions and has been awarded $15 million by the U.S. National Science Foundation (NSF).
“The new center is very exciting,” said Ruth Harris, a senior scientist with the U.S. Geological Survey’s Earthquake Science Center, who is not involved with the project. “Cascadia has significant earthquake risks, so this is an important region to focus on,” she explained.
A Better Understanding of Subduction Zones
The Cascadia Subduction Zone is a 1,100-kilometer-long (700-mile-long) tectonic plate boundary separating North America from the subducting Juan de Fuca plate. The area’s main fault, called a megathrust, dives eastward beneath the coast and major cities such as Seattle and Vancouver, B.C. A patchwork of smaller faults dissects the upper crust in Cascadia, posing a lesser but still significant hazard. Although the megathrust sees regular quiet movement, a major earthquake has not struck the fault since 1700. That event, estimated at magnitude 9.0, sent tsunami waves across the Pacific.
Despite the hazard, earthquake preparedness in the Pacific Northwest is lagging, said Diego Melgar, a seismologist at the University of Oregon and CRESCENT’s principal investigator.
Unlike in California, where frequent moderate-magnitude earthquakes have spurred residents and policymakers into action, major earthquakes are infrequent in the Pacific Northwest. As a result, the seismic hazard went unrecognized for generations. “Scientists used to refer to Cascadia as an extinct subduction zone,” Melgar said. “It wasn’t until the 1990s that we realized, oh, crap, it’s still capable of making big earthquakes.”
Researchers have made progress in the past few decades, but there is a need for further research, said Harold Tobin, a professor at the University of Washington and director of the Pacific Northwest Seismic Network (PNSN), which monitors earthquakes in the region. “There has been a strong focus in the U.S. on earthquakes along transform faults such as the San Andreas Fault, but we know less about subduction zones,” he said. “We need to bring our understanding of subduction zones up to the same level as for transform faults.”
CRESCENT will bring together earthquake scientists working in Cascadia to address that gap.
One of the center’s primary goals is creating a community-vetted model of the faults in the region. “There are tons of crustal faults that we know surprisingly little about,” Melgar said. CRESCENT researchers will use data from the PNSN, field observations, experiments, and computer modeling to better understand the location and the 3D structure of the faults.
Another outstanding issue is the extent to which friction keeps the subduction zone locked, preventing slip. Locked plates accumulate stress, which eventually is released in earthquakes. Strong frictional locking can produce correspondingly strong earthquakes. The locked subduction zone near Japan, for instance, has produced many large shocks in recent history, including the 2011 magnitude 9.0 Tōhoku earthquake.
Most researchers have agreed that part of the Cascadia Subduction Zone is strongly locked, but the fine-scale details of where it is locked and where it is continuously slipping are unclear, making it difficult for seismologists to forecast earthquake and tsunami hazards.
“CRESCENT can be the town square where people get together to talk about these problems and solve them,” Melgar said. The center’s research will help to assess the likelihood of earthquakes, tsunamis, and landslides that could threaten communities in Cascadia.
Translating Science into Informed Choices
Aside from facilitating research, CRESCENT will foster connections between scientists and policymakers, local communities, and private industry. “We want to make sure the science outcomes are useful and translate into informed choices at all levels,” Tobin said.
CRESCENT is an “exciting opportunity,” said Tim Dawson, manager of the Seismic Hazards Program at the California Geological Survey, who is not involved with CRESCENT. “The multidisciplinary approach. . .will lead to new insights into the workings of subduction zones with practical applications for public safety, building more resilient communities, and developing the next generation of earthquake scientists.”
—Caroline Hasler (@carbonbasedcary), Science Writer