Cascadia subduction zone earthquake history, 8000 B.C. to present

A total of forty-one (41) magnitude 8+ (thin red line) and magnitude 9+ (thick red line) Cascadia subduction zone earthquakes and tsunamis have occurred in the past ten thousand years. That's roughly one every 243 years, on average. And the last one occurred in January, 1700, over 315 years ago.

And, the recent history is actually much worse. Between 3950 B.C. and today (a total of 5965 years), there have been twenty-nine (29) magnitude 8 or higher earthquakes. That's an average of one every 206 years. And the last one occurred over 315 years ago. We are WAY overdue!