‘Researchers have said it’s not a question of if but when a quake of at least 9.0 magnitude will strike in the Cascadia Subduction Zone, a fault that stretches from Vancouver Island to Northern California.
The last major quake along the entire Cascadia fault occurred in 1700. It dropped parts of the Olympic Peninsula coast by 5 feet and triggered a tsunami that pounded the Pacific Northwest and washed away houses in Japan…’
‘The Really Big One’
Background from The New Yorker/July 20, 2015:
‘Most people in the United States know just one fault line by name: the San Andreas, which runs nearly the length of California and is perpetually rumored to be on the verge of unleashing “the big one.” That rumor is misleading, no matter what the San Andreas ever does. Every fault line has an upper limit to its potency, determined by its length and width, and by how far it can slip. For the San Andreas, one of the most extensively studied and best understood fault lines in the world, that upper limit is roughly an 8.2—a powerful earthquake, but, because the Richter scale is logarithmic, only six per cent as strong as the 2011 event in Japan.