Lituya Bay Earthquake and Tsunami

Date: July 9, 1958 • Location: Yakutat City and Borough, United States

An earthquake struck Lituya Bay, Alaska; the subsequent megatsunami, the largest in modern times, reached an elevation of 1,720 ft (524 m).

An earthquake occurred in Lituya Bay, Alaska, on July 9, 1958, at 22:15:58 PST with a moment magnitude of 7.8 to 8.3 and a maximum Mercalli intensity of XI (Extreme). The strike-slip earthquake took place on the Fairweather Fault and triggered a rockslide of 30 million cubic meters and about 90 million tons into the narrow inlet of the bay. The impact was heard 80 kilometers (50 mi) away, and the sudden displacement of water resulted in a megatsunami that washed out trees to a maximum elevation of 524 meters at the entrance of Gilbert Inlet. This is the largest and most significant megatsunami in modern times; it forced a re-evaluation of large-wave events and the recognition of impact events, rockfalls, and landslides as causes of very large waves.