The 1958 Lituya Bay earthquake occurred on 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 (40 million cubic yards) and about 90 million tons into the narrow inlet of Lituya Bay, Alaska. The impact was heard away, and the sudden displacement of water resulted in a megatsunami that washed out trees to a maximum elevation of 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. Event outline Lituya Bay is a fjord located on the Fairweather Fault in the northeastern part of the Gulf of Alaska. It is a T-shaped bay with a width of and a length of . Lituya Bay is an ice-scoured tidal inlet with a maximum depth of . The narrow entrance of the bay has a depth of only . The two arms that create the top of the T-shape of the bay are the Gilbert and Crillon inlets and are a part of a trench on the Fairweather Fault. In the past 170 years Lituya Bay has had four other tsunamis over 100 ft: 1854 (), 1899 (), 1936 (), and 1958 (). Near the crest of the Fairweather Mountains sit the Lituya and the North Crillon glaciers. They are each about long and wide with an elevation of . The retreats of these glaciers form the present "T" shape of the bay, the Gilbert and Crillon inlets. Earthquake The major earthquake that struck on the Fairweather Fault had a moment magnitude of 7.8 and a maximum perceived intensity of XI (Extreme) on the Mercalli intensity scale. The epicenter of the quake was at latitude 58.37° N, longitude 136.67° W near the Fairweather Range, east of the surface trace of the Fairweather fault, and southeast of Lituya Bay. This earthquake had been the strongest in over 50 years for this region: the Cape Yakataga earthquake, with an estimated magnitude of 8.2 on the Richter scale, occurred on September 4, 1899. The shock was felt in southeastern Alaskan cities over an area of , as far south as Seattle, Washington, and as far east as Whitehorse, Yukon, Canada.