What Seattle's recent quake streak means for the "Big One"
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A flurry of earthquakes in the Seattle area over the last couple of weeks has some residents asking if that means the "Big One" is on its way.
Why it matters: Scientists say it's not a question of if, but when, the Cascadia subduction zone — a 700-mile offshore fault that runs from Canada to California — unleashes a massive earthquake, triggering a tsunami and spelling one of the worst natural disasters on the continent.
Driving the news: Since Feb. 22, the Pacific Northwest Seismic Network (PNSN) recorded five notable earthquakes in western Washington. The most recent was a 3.9 magnitude quake near Port Angeles on March 5.
The intrigue: Do these quakes tell us anything about the future?
- Perhaps, said Harold Tobin, the director of PNSN and Washington's state seismologist.
What they're saying: The recent series of temblors isn't necessarily a warning sign, he told Axios.
- It confirms we live in a seismically active region, and while the recent spike in quakes is above average, it's still within the normal range.
Yes, but: A 4.5-magnitude earthquake near Friday Harbor on March 3 has a small chance of being a foreshock to a larger event within the next month or so, he said.
- "It is not impossible that a larger earthquake could follow."
The big picture: A major earthquake strikes the Cascadia subduction zone roughly every 550 years. The last one hit in 1700 — 325 years ago, which means a repeat event could happen any time, Tobin previously told Axios.
What's happening: The Cascadia subduction zone is where the Juan de Fuca tectonic plate is slowly sliding beneath the North American plate.
- The plates are locked, having nowhere to go, but the pressure continues to grow.
- When they finally slip, the resulting quake could cause the coastline to drop and shift, turn some ground to mush and collapse roads, bridges and buildings.
- Unlike California's San Andreas Fault, which produces earthquakes that max out around 8.2 magnitude, Cascadia can produce 9-magnitude quakes, comparable to Japan's 2011 earthquake and tsunami, which caused the Fukushima nuclear disaster.
Zoom in: Seattle experiences three types of earthquakes, each with distinct impacts, per the city:
- Crustal or shallow quakes cause intense shaking near the epicenter but weaken quickly.
- Intraplate or deep quakes, like the 2001 Nisqually quake, cause less surface shaking.
- Subduction zone quakes are the most powerful.
Get your home earthquake-ready by anchoring heavy furniture, water heaters and appliances and putting breakable things onto lower shelves.
- Identify safe spots in each room to drop, cover and hold on.
- Build an emergency kit with at least two weeks' worth of food, water and essentials, including first aid supplies, flashlights, batteries, medications and cash.
- Pack an accessible go-bag.