Queen Charlotte - Fairweather fault system

The Queen Charlotte and Fairweather faults are part of a long fault system that mark the eastern boundary of the Pacific plate and the western boundary of the North American plate. The Pacific plate moves in a northwestward direction relative to the North American plate, creating a transform boundary, the name given to the interface between two plates moving horizontally in opposite directions. The fault associated with a transform boundary is a strike-slip fault. The Queen Charlotte and Fairweather faults are very similar to some of the most well known strike-slip faults in the world; the faults associated with California's San Andreas fault system.

At the northern end of the Queen Charlotte-Fairweather fault system is the Fairweather fault, a strike-slip fault with right lateral movement. The Fairweather fault is visible on land for about 280 kilometers from Cross Sound northwestward to its junction with the St. Elias fault in the vicinity of Yakutat Bay. Seismic exploration methods have projected the Fairweather fault just offshore of the Alexander Archipelago from Cross Sound to the mouth of Chatham Strait. At this point, the fault is believed to connect with the Queen Charlotte fault. The Queen Charlotte fault, which extends southeastward from Chatham Strait past the Queen Charlotte Islands, is also a strike-slip fault with right lateral movement.

Four major earthquakes have been linked to the Queen Charlotte-Fairweather fault system in the last century. In 1927 a magnitude 7.1 (Ms - surface wave magnitude) earthquake occurred in the northern part of Chichagof Island, in 1949 a magnitude 8.1 (Mw - moment magnitude) earthquake occured along the Queen Charlotte fault near the Queen Charlotte Islands, in 1958 movement along the Fairweather fault near Lituya Bay created a magnitude 7.9 (Ms) earthquake, and in 1972 a magnitude 7.4 (Ms) earthquake occured near Sitka. The 1958 Lituya Bay earthquake, which was felt as far away as Seattle, Washington, caused a large rockslide which deposited the contents of an entire mountainside into the bay. The gigantic wave that resulted from this rockslide scoured the shores of the bay down to bedrock and uprooted trees as high as 540 meters above sea level. Fishing boats were carried on the wave at a reported height of at least 30 meters over the spit at the entrance to the bay and tossed into the open ocean.

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Updated: October 2006