What is California’s biggest earthquake and tsunami threat? It’s not the San Andreas fault, but actually the Cascadia subduction zone.
The San Andreas fault is of course capable of producing The Big One. But The Really Big One will probably come from the Cascadia subduction zone, located off the coast of the Pacific Northwest. As reported by the Cascadia Region Earthquake Workgroup, a “megathrust” quake along the Cascadia subduction zone could destroy Seattle and a tsunami inundate many areas to the south.
What history tells
Showing back in history, we discover that the Cascadia subduction zone produced strong and destructive earthquakes (up to magnitude 9.0) such as on Jan. 26, 1700, when stretches of the Pacific coastline dropped by as much as five feet, allowing a huge tsunami to devastate everything along the shore. You imagine such a powerful earthquake striking now again on this very populated coast! Terrible!
Why are subduction zones prone to large tsunamis?
Subduction zones are especially prone to large tsunamis because as one plate is pushed beneath another, the plates continue to push and lock against each other until stress builds up so much that they slip. Scientists are worried this is currently happening at the Cascadia subduction zone, and any time energy is built up by shifting plates, a large earthquake could occur. Watch this video:
How much time would you have for evacuation?
According to the LA Times, residents would only have about 15 minutes to get to safety. Pretty tight, not? In Grays Harbor County, Wash., they’re beginning to build vertical evacuation centers atop sturdy gymnasiums that will allow teachers and students to quickly evacuate to higher ground in case a massive earthquake pushes a tsunami toward the coast.