<P> The 1700 Cascadia earthquake occurred along the Cascadia subduction zone on January 26 with an estimated moment magnitude of 8.7 -- 9.2 . The megathrust earthquake involved the Juan de Fuca Plate from mid-Vancouver Island , south along the Pacific Northwest coast as far as northern California . The length of the fault rupture was about 1,000 kilometers ( 620 miles ) , with an average slip of 20 meters ( 66 ft ) . </P>
what is the largest magnitude earthquake that has occurred in the pacific northwest
The 1700 Cascadia earthquake