The Cascadia subduction zone has been mapped over 1,000 km (621 miles) from northern Vancouver Island to Cape Mendocino in northern California. Scientists can see the bend of the subducting plate in an image of the coastline. When the Juan de Fuca subduction zone locks and stores strain, it produces damaging Cascadia earthquakes.

Cascadia is regarded as one of the most likely sources of giant earthquakes globally, and much effort has gone into estimating its hazard potential.