TOLEDO — For residents of the Pacific Northwest, the threat of natural disasters, ranging from forest fires to floods, is always prevalent.
However, aside from rivers flooding and forests burning every year, a much more dangerous and potentially deadly natural disaster threat looms — a massive earthquake triggered by a “megathrust” of the Cascadia Subduction Zone tectonic plate fault line.
According to the Pacific Northwest Seismic Network, the Cascadia Subduction Zone is a section of fault line stretching off the coast of British Columbia down to Cape Mendocino, California, separating the Juan de Fuca and North America tectonic plates.
Historical geological data shows these major earthquake events occur at an estimated “~500-year recurrence” rate. With the last one occurring back in 1700, scientists believe there’s a chance the next one may happen within the next few decades in the region, according to a 2025 U.S. Geological Survey (USGS) study.
In the study, geophysists, geologists and seismologists from both the USGS and the University of Washington estimated there is a 10% to 15% chance of a “megathrust” occurring in the Cascadia Subduction zone over the next 50 years, producing an earthquake of magnitude 9.0 or higher.
While Lewis County residents don’t have to worry about the tsunami threat created by that earthquake, like those closer to the Pacific Coast, the massive earthquake itself still poses a catastrophic damage threat to buildings, bridges, hydroelectric dams and other infrastructure in the county.
On Wednesday, Sept. 16, more than 40 Toledo-area residents attended a community meeting at the Steamboat Landing community center, hosted by Lewis County Emergency Management and Tacoma Power officials, to discuss what to do in a worst-case scenario where the region is hit by a 9.0 or higher earthquake. Officials also conducted a test of Toledo’s evacuation alarm before the meeting.
Should the worst case scenario occur, Lewis County Emergency Management Deputy Director Erika Katt recommended residents have at least two weeks worth of food, water, medicine and any other supplies they might need.
“Everywhere else in the United States, it’s three days (worth of emergency supplies). Nearly all places in the United States is three days. Why would it be two weeks here? The Cascadia earthquake, they know it’s going to be bad,” Katt said. “They know it’s going to take a while to get to all the people. Where do you think all the rescue people are gonna go? To the masses. Are we the masses? No.”
Given the potential damage to roads and bridges in the area and the possibility of rescuers having to concentrate on damage in much more populous areas compared to rural Lewis County, residents here may have to rely on their neighbors for help.
“We can’t do this alone. Know what your neighbor has. So if I have a generator but I run out of fuel but my neighbor has fuel, let’s work together to have power,” Katt said, adding: “Talk to each other, and have those group meetings.”
Katt added residents should also ensure items in their homes are not a fall hazard in the event of an earthquake. One attendee recommended having an emergency kit in vehicles — which included shoes good for walking in — should a resident be away from home when a major earthquake occurs.
Should a resident have pets, Katt recommended having an emergency supply of pet food, too, along with any medicines they may need. Residents should also keep copies of important insurance documents, deeds to houses and other important documents.
Katt recommended residents sign up for the ShakeAlert Earthquake Early Warning system, a USGS program focused on sending out automated messages in an effort to give people time to prepare, even if it’s just a few seconds before the shaking of the earthquake begins. To sign up for ShakeAlert, visit https://www.shakealert.org/.
Should someone be in a building and have time to get out, Katt recommended doing it. However, once the shaking starts, the best thing to do is to duck and cover under a “sturdy object,” even inside a building.
Those driving during a major earthquake should pull over in a safe location away from large buildings, trees and power lines, park and turn on the vehicle’s hazard lights, and wait for the shaking to subside.
“If you’re in a wheelchair, put on the brakes and protect your head and neck,” Katt said. “If you can’t get on the ground or you’re not as bendy as you once were, you might just need to stay in your seat and secure yourself and protect your head and neck the best you can.”
Given Toledo’s location downriver from both the Mayfield and Mossyrock hydroelectric dams on the Cowlitz River, some residents also had questions about the risk of a dam collapse triggering catastrophic flooding during a major earthquake.
According to Tacoma Power Emergency Manager Jayson Lelli, the reservoirs behind the dams are already being kept at lower-than-average levels while studies on the dams are completed to renew their Federal Energy Regulatory Commission (FERC) approval.
Tacoma Power coordinates with Lewis County Emergency Management’s Lewis County Alert program, and Lelli recommended residents sign up for alerts from the county — as in the event of a smaller emergency, Tacoma Power will contact the county first to let them know there’s an issue.
Lelli also stated he believed there was no risk for a catastrophic event like a complete dam collapse, even if a major earthquake hits.
“The dam is not just going to disappear. There’s never been an arch-dam failure in the world,” Lelli said.
“I live right below the dams that you guys are concerned about,” Tacoma Power Cowlitz River Project Manager Chad Chalmers added. “My dams are safe. My family lives right below it. We go through an annual FERC inspection. Yearly, the federal government comes out and does a FERC inspection. They came out at the end of July, performed an inspection, and had nothing to report back to me. They said everything looked great … There’s rumors out there about maintenance at the facilities and whatnot. My staff works very hard to maintain our facilities.”
He said Tacoma Power staff perform their own daily inspections on various areas and components of the dam, and report any changes to their managers.
To learn more about both the Mayfield and Mossyrock dams, visit Tacoma Power’s website at https://tinyurl.com/mvceb8ej. Those wishing to sign up for Lewis County Alert can do so on the county’s website at https://tinyurl.com/5dt4ta4f.
To view the 2025 USGS Earthquake report for the Pacific Northwest, visit the USGS website at https://tinyurl.com/4dmhvu68.
