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NW Region Hazards and Risks
We offer CERT training because our Washington region is ranked number four for the heaviest cumulative federal disaster burden, with over 200 recorded FEMA disaster declarations since 1953. If you asked people to list the hazards and risks in Western Washington, most would include winter storms, power outages, flooding, forest fires, earthquakes, volcanoes, liquefaction, lahars and pandemics.
A disaster is a sudden event, such as an accident or a natural catastrophe, that causes great damage or loss of life. In a disaster, first responders will be overwhelmed and CERT-trained volunteers have the skills to help themselves, their families, neighborhoods, and the community. The Washington Emergency Management Division recommends everyone is Two Weeks Ready.
Fault Zones: The Washington Geological Survey provides active fault and tsunami inundation maps.
Historical Data: Review past events using the 10,000 Years of Cascadia Earthquakes Timeline.
DISASTER FACTS | Ready.gov - Know what disasters and hazards could affect your area and learn what to do before, during, and after each type of emergency.
EARTHQUAKE RISKS
Three major earthquake threats are Cascadia Subduction Zone (CSZ), Seattle Fault and the South Whidbey Island Fault
EARTHQUAKE RISKS
Three major earthquake threats are Cascadia Subduction Zone (CSZ), Seattle Fault and the South Whidbey Island Fault
1. Cascadia Subduction Zone (CSZ)
The Cascadia Subduction Zone (CSZ) is a 600-mile fault that runs from northern California up to British Columbia. It is an overlapping joint between tectonic plates, part of the Earth’s crust that floats on layers of molten rock.
2. South Whidbey Island Fault
2. South Whidbey Island Fault
The South Whidbey Island Fault is dangerous. It’s significantly larger than the Seattle Fault, and South Whidbey could hand us a magnitude 7.5 earthquake. A 7.5-magnitude earthquake is capable of causing major destruction over a large area. It could also set off quakes on connected faults. Many of the other earthquake faults in the region could be connected to the South Whidbey in a system similar to the San Andreas fault in California. Because the South Whidbey fault is shallow, running beneath Mukilteo and southeast to Woodinville, south Snohomish County could be at increased risk, Snohomish County emergency services director John Pennington said. “The reality is when this earthquake hits, there will be some heavy losses,” he said. Snohomish County is better prepared now for such a quake than it was several years ago, Pennington said.
What to Expect Bothell, WA has a very high earthquake risk, with a total of 983 earthquakes since 1931. The USGS database shows that there is a 81.93% chance of a major earthquake within 50 Km (31 miles) of Bothell, in the next 50 years. The largest earthquake within 30 miles of Bothell, WA was a 5.8 Magnitude in 1996.
LINKS
LINKS
Natural and technological hazards threaten our citizens and communities. Analysis of potential hazards and planning for such events will allow you to mitigate the risks, enhance safety and reduce recovery time.
Definitions:
Lahars—Dangerous mudflows that occur when a landslide or eruption rapidly melts snow and ice on a volcano.
Landslides — Dangerous downhill movements of rock, soil, or debris
Faults — Fractures in the Earth's crust that produce earthquakes.
Tsunami — A powerful and destructive series of ocean waves caused mainly by earthquakes and landslides.
Liquefaction — when wet, loose soil temporarily loses its strength and acts like a thick liquid during an earthquake.
Seiche (pronounced "saysh") — . You can think of it like water sloshing back and forth in a giant bathtub, but it happens in lakes, bays, or reservoirs
Southern Whidbey Island Fault (SWIF)
Southern Whidbey Island Fault (SWIF)
Location and known extent (prior to 2004) of Southern Whidbey Island Fault (SWIF). Also shown: Devils Mountain, Strawberry Point, and Utsalady Point faults (crossing northern Whidbey Island), Seattle Fault zone, southern part of Rattlesnake Mountain Fault Zone, Tokul Creek Fault (striking NNE from RMFZ). Not shown: southeastward extension of SWIF and various faults running northward from the RMFZ and east of Everett.
The Seattle Fault is a zone of multiple shallow east-west thrust faults that cross the Puget Sound Lowland and through Seattle (in the U.S. state of Washington) in the vicinity of Interstate Highway 90.It's considered capable of a magnitude 7. That may not sound like much more than the magnitude 6.8 quake of 2001 based on the numbers, but that the Nisqually quake occurred some 30 miles underground. Then consider that the Seattle Fault is a complex of faults with various branches that run at or just below the surface.
“The risk is complicated, but there are millions of people who live in the Seattle area,” said Forson. “What we know about this fault is that it’s ruptured may times in the past…it will happen again. We just don’t know when.”
Across the northern portion of Bainbridge Island, light radar or lidar images taken from airplanes clearly show (below) what geologists say is the Seattle Fault running right on the surface. Another piece can be seen under the elevated lanes of northbound Interstate 5 in South Seattle not far from the Rainier brewery.
With the current preparedness levels of Washington (read the Cascadia Rising Report 2016), we can anticipate being without services and assistance for at least 2 weeks, if not longer, when the Cascadia Subduction Zone earthquake occurs. While this will be difficult to overcome, our citizens, businesses, schools, government, and communities as a whole can take steps to get prepared. Take action now by actively planning and preparing yourself and your community to be ready for two weeks for disasters.
Volcano Hazards
Volcano Hazards
The Pacific Northwest faces significant volcanic risks from the Cascade Range, where active stratovolcanoes threaten more than 10 million residents and critical regional infrastructure. Check official maps and resources at the Washington State Department of Natural Resources and the USGS Cascades Volcano Observatory.
Lahars (Volcanic Mudflows): Fast-moving rivers of melted ice, water, ash, and rock that rush down river valleys at up to 30–50+ mph. They can travel more than 50 miles from a peak and devastate low-lying communities (such as river valleys around Mount Rainier).
Ashfall (Tephra): Fine, sharp rock and glass particles carried hundreds of miles by wind. Heavy accumulation can collapse building roofs (at around 20 cm depth), ruin machinery and electronics, ground aviation, and cause severe respiratory problems.
Pyroclastic Density Currents: Superheated avalanches of gas, ash, and rock moving up to 700 km/h with temperatures reaching 1,000°C, destroying everything in their path near the source.
Lava Flows & Domes: Cascade lava is typically thick and viscous. It moves slowly and usually stays within a few miles of the vent, though dome collapses can trigger pyroclastic flows.
Highest-Threat Volcanoes in the PNW
The USGS National Volcanic Threat Assessment designates several regional peaks as High or Very High Threat based on past activity and nearby populations:
Very High Threat: Mount Rainier, Mount St. Helens, Mount Baker, Glacier Peak, and Mount Adams (High) in Washington; Mount Hood, Crater Lake, Newberry, and Three Sisters in Oregon.
Mount Rainier: Considered one of the most dangerous due to its massive glacial ice cap, steep height (4,392 m), and dense suburban encroachment from the Seattle-Tacoma metro area.
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