These cartoons show the difference between shallow subduction of the Juan de Fuca plate beneath Washington versus the steeper subduction beneath Oregon. The y-axis shows depth in kilometers. The red-brown coloring of the subducting slabs shows the zone that can rupture. In the above example of Washington, that zone is much greater in area because of the shallow dip angle. The plate is flatter here, so there’s more area in the zone that’s prone to break. Credit: Harold Tobin