The Fairweather Fault is a right-lateral strike-slip fault in southeastern Alaska, running onshore along the flank of the Fairweather Range near Glacier Bay and continuing offshore where it connects to the Queen Charlotte Fault to the south. Together they form the transform boundary along which the Pacific Plate grinds northwestward past North America at several centimetres per year.
Slicing through some of the steepest coastal mountains and tidewater glaciers on Earth, the fault sits in a remote but tectonically vigorous corner of the continent. Its rapid slip rate makes it one of the fastest-moving strike-slip faults in North America and a frequent source of large earthquakes.
The fault ruptured in the 1958 Lituya Bay earthquake (magnitude 7.8), which shook a mountainside loose into the narrow bay and triggered a megatsunami whose water surged an astonishing 524 metres up the opposite slope — the highest wave run-up ever recorded. The event remains a stark illustration of how a strike-slip fault can unleash catastrophic secondary hazards.