Deepest Earthquakes in the United States

Most earthquakes occur in the upper 20 km of the Earth's crust, but some strike much deeper. Deep earthquakes — those below 70 km — typically occur in subduction zones where one tectonic plate dives beneath another. In the US, the deepest earthquakes are concentrated in Alaska's Aleutian subduction zone and beneath the Pacific Northwest.

Depth affects how an earthquake is felt at the surface. A deep earthquake's energy spreads over a wider area but arrives weaker at any single point, while a shallow earthquake concentrates its energy and can cause intense local shaking. A magnitude 5.0 at 10 km depth is far more destructive than the same magnitude at 200 km.