The 1700 Cascadia Earthquake

The last time there was a megathrust earthquake in the contiguous 48 states was January 26, 1700, when a thousand-kilometer long stretch of the North American plate slipped 20 meters just off the coasts of Washington and Oregon. You can read more about that here:
1700 Cascadia earthquake

Megathrust earthquakes are an ordinary part of the background noise of Earth's geology, but they're bad news bears for civilization. When large parts of Earth's crust slip beneath the lithosphere in a matter of minutes the planet's axis shifts, days perceptibly shorten, and tsunamis wander across oceans. There have been three megathrust earthquakes in the last decade, one near Sumatra, one in Chile, and one near Honshu. That kind of frequency is rare, geologically speaking. The last one before the 2004 Indian Ocean earthquake was 40 years earlier, in Alaska. Interestingly, the date of the 1700 Cascadia earthquake is known so precisely because it was powerful enough to send large tsunamis to Japan later that day. The Japanese kept better written records than the Chinook back then.

Big earthquakes are less common in Cascadia than they are in Japan, Alaska, and the South American west coast, but they're no less hazardous. The fault that caused the Tohoku earthquake of two years ago is almost identical to the fault off our northwest coast. There's no sense worrying about it unproductively, but it's something to be respected and prepared for from Crescent City to Victoria.