The last great megathrust earthquake in the Cascadia subduction zone was in 1700, a 1000–km long rupture that is documented by studies of the resulting tsunami in Japan, by Native American oral traditions, and by geologic deposits from tsunami and offshore turbidity flows caused by the intense shaking and ground deformation associated with the earthquake. Scientists know it has the potential for large earthquakes – as big as Therefore, we are now in the risk zone of another earthquake. Researchers have plotted movement of the tsunami from 1700 megaquake There haven’t been many widely felt quakes along the Cascadia megathrust, certainly nothing that would rival a catastrophic event like the 1989 Loma Prieta earthquake along the active San Andreas in California. Terrifying simulation shows how the Pacific Northwest could be decimated by a megaquake caused by the Cascadia fault. That doesn’t mean it will stay quiet, though. USGS Powell Center Cascadia Earthquake Hazards Working Group; Fort Collins, Colorado, 25–29 March 2019 Most people don't associate the US Pacific Northwest with earthquakes, but maybe they should. The 1700 Cascadia earthquake occurred along the Cascadia subduction zone on January 26 with an estimated moment magnitude of 8.7–9.2. Addressing Cascadia Subduction Zone Great Earthquake Recurrence .

The Cascadia Subduction Zone has not produced an earthquake since 1700 and is building up pressure where the Juan de Fuca Plate is subsiding underneath the North American plate.

"The last megathrust earthquake originating from the Cascadia subduction zone occurred in 1700 A.D. Currently, scientists are predicting that there is about a 37 percent chance that a megathrust earthquake of 7.1+ magnitude in this fault zone will occur in the next 50 years.