It's not just the potential for shaking that worries us. Our part of the world sits atop the Cascadia Subduction Zone, and movement in that zone far beneath us could bring a gigantic earthquake.
But the earthquake could well come with a big wall of water, a tsunami generated in the Pacific.
That's Ron Harris's area of expertise; he's a geology professor at Brigham Young University and the tsunami expert for SEG, the Society of Exploration Geophysicists. We get a visit from Dr. Harris about the dynamics of a big Pacific tsunami, and how people close to the ocean can prepare.
He left us with the 20-20-20 rule:
- 20 seconds or more of shaking will probably produce a tsunami
- 20 minutes is all people at the ocean will have to evacuate
- 20 meters in elevation (65 feet) is how high they should get—at a minimum—to stay clear of water