A seismic monitoring station crowned Burley Mountain in the Gifford Pinchot National Forest last August, completing a network that researchers believe could save lives when the Pacific Northwest's largest earthquake hazard strikes. With that final installation, the ShakeAlert earthquake early warning system reached its planned goal of 569 seismic stations across Washington and Oregon, putting the technology on solid ground after a five-year buildout that began in 2021.
The system works by detecting ground motion from earthquakes before people feel the shaking, giving those precious seconds or minutes to drop, cover and hold on. When an earthquake exceeds magnitude 5, ShakeAlert automatically sends alerts through the Wireless Emergency Alerts program to millions of phones across the region. Schools can connect their PA systems to the network for rapid updates, transit agencies can slow trains to prevent derailment, and fire station doors automatically unlock to allow trucks out even if power is lost. It's early warning infrastructure built into the fabric of public safety.
Yet Harold Tobin, director of the Pacific Northwest Seismic Network at the University of Washington, sees the work as incomplete. "When we launched ShakeAlert, we felt confident that we had enough seismic stations to do a good job with early warning, but that wasn't the optimal number," Tobin said. "Now, with the buildout complete, we have coverage where it was lacking at launch." That coverage proved itself just over a year ago when a midsized earthquake near Orcas Island tested the system in Washington for the first time. Multiple seismometers detected the signal, ran it back to headquarters for verification, and sent warnings to nearby residents through MyShake apps and Android devices—all within seconds. The system worked flawlessly, but it revealed a critical weakness.
The real threat to the Pacific Northwest doesn't come from beneath land, but from the ocean. The Cascadia Subduction Zone, a massive fault off the coast where two tectonic plates collide, poses what Tobin describes as "the biggest earthquake hazard" in the region. The challenge is fundamental: "Our seismic network—hundreds and hundreds of stations—is on land, but the biggest earthquake hazard comes from off our coast. Earthquake detection works much better when the earthquake is in the area of your network, not off to one side."
To address this gap, researchers are exploring offshore expansion. Currently, only seven offshore seismic sensors exist near the Pacific Northwest coast—five off Vancouver Island and two off Oregon—and none feed into ShakeAlert. A University of Washington-led project this summer will add four new sensors to an undersea cable spanning hundreds of seafloor miles across the subduction zone twice. The technology exists; Japan demonstrated it by installing more than 200 offshore seismometers at a cost of $120 million following the devastating 2011 earthquake. Zoe Krauss, a UW postdoctoral researcher, recently presented evidence to the Seismological Society of America showing the potential impact of adding offshore seismic monitoring to the Pacific Northwest network.
The work reflects a broader truth about earthquake preparedness: early warning systems can't eliminate the danger, but they can transform how communities respond to it. Each new sensor, whether anchored on Burley Mountain or on the seafloor miles offshore, represents another chance for people to protect themselves when the ground shakes.