![]() ![]() Rockfall Damage from the 1958 Lituya Bay megatsunami can be seen in this oblique aerial photograph of Lituya Bay, Alaska as the lighter areas at the shore where trees have been stripped away. The shock was felt in southeastern Alaskan cities over an area of 400,000 square miles (1,000,000 km 2), as far south as Seattle, Washington, and as far east as Whitehorse, Yukon, Canada. 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 epicenter of the quake was at latitude 58.37° N, longitude 136.67° W near the Fairweather Range, 7.5 miles (12.1 km) east of the surface trace of the Fairweather fault, and 13 miles (21 km) southeast of Lituya Bay. 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 retreats of these glaciers form the present "T" shape of the bay, the Gilbert and Crillon inlets. They are each about 12 miles (19 km) long and 1 mile (1.6 km) wide with an elevation of 4,000 feet (1,200 m). Near the crest of the Fairweather Mountains sit the Lituya and the North Crillon glaciers. ![]() 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. The narrow entrance of the bay has a depth of only 33 feet (10 m). Lituya Bay is an ice-scoured tidal inlet with a maximum depth of 722 feet (220 m). It is a T-shaped bay with a width of 2 miles (3 km) and a length of 7 miles (11 km). Lituya Bay is a fjord located on the Fairweather Fault in the northeastern part of the Gulf of Alaska. 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. 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 (1,719 feet) at the entrance of Gilbert Inlet. 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 1958 Lituya Bay earthquake occurred on Jat 22:15:58 PST with a moment magnitude of 7.8 to 8.3 and a maximum Mercalli intensity of XI ( Extreme). The lighter green areas along the shore indicate places where forests are younger than older trees (darker areas) that were not affected by the tsunami. The damaged trimline is still imprinted in the forest. ![]()
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