The 1700 Cascadia earthquake was part of a sequence of at least four great earthquakes that occurred in the region in the past 3,500 years. These earthquakes are known as the Cascadia megathrust earthquakes and are caused by the sudden rupture of the Cascadia Subduction Zone, a fault line where the Juan de Fuca Plate is subducting under the North American Plate. The other great earthquakes in the sequence occurred in approximately 1300, 1600, and 1857.