It's got to be nerve-wracking to be a seismologist monitoring the Cascadia fault. Running perilously close to the major cities of Seattle, Vancouver, Portland, and several other populations centers in the Pacific Northwest, it's easily the most dangerous fault in North America. Lined with state-of-the art sensors, scientists can watch its every move.
And move it does. Every 15 months or so, it slips - ever so slightly - in an event scientists call "Episodic Tremor and Slip" or ETS. It's just about equivalent to seeing the rise and fall of a sleeping dragon's chest, and hoping with every breath that it doesn't wake up.
In this recent simulation, the Washington State Department of Transportation showed how Seattle's waterfront highway and docks would be devastated by a magnitude 7.0 earthquake:
Trouble is, scientists expect the Cascadia megathrust could pop off a magnitude 9.0 quake, which would be 1,000 times more powerful than the 7.0. That pancaked freeway was pretty scary to watch, but when the big one hits, it might be the least of the city's problems.