1946 Aleutian Islands earthquake

and seismicity of Alaska The Aleutian Islands are a group of 14 large and 55 smaller volcanic islands situated between mainland Alaska and Kamchatka. They are situated along the Aleutian Trench as they were formed by the active subduction of the oceanic Pacific plate underneath the continental crust of the North American plate. The western portion of the trench becomes more and more oblique until near the Commander Islands where faulting becomes nearly exclusively strike-slip and causes earthquakes such as the 2017 Komandorski Islands earthquake. The trench ends where the Kuril-Kamchatka Trench begins in the west. The collision ends slightly further east, where the Queen Charlotte Fault becomes the dominant fault of the tectonic regime. ==Earthquake==

The earthquake struck at 02:29 local time on April 1, 1946, at a shallow depth of . The earthquake was very large, but the maximum felt intensity was only a VI. The earthquake was originally thought to be a rather smaller earthquake of 7.4, however further research uncovered that this was truly a much larger event, but with a hidden seismic signature. This event shows the classic signs of a tsunami earthquake as the surface-wave magnitude was very low compared to the moment and tsunami magnitudes, and the tsunami height was far larger than expected for the surface wave magnitude. The very high tsunami magnitude value is due to the sheer strength of the waves. It was calculated by using tsunami run up from Honolulu, Hilo, and the average of stations in California. Even excluding the values given by Hilo (the highest ), the tsunami magnitude is at least 9.1. The earthquake was originally thought to be a strike-slip earthquake, and later a strike slip earthquake with a normal faulting component. These erroneous focal mechanisms were due to a lack of stations recording the earthquake. However, modeling of the S wave, rather than the P wave helped to uncover both the true magnitude of the earthquake, as well as the widely accepted thrusting mechanism. This thrust mechanism is consistent with a subduction earthquake helping to relieve stress on the Aleutian Trench. ==Tsunami==

At Unimak Island, tsunami run-up reached . The tsunami earthquake aspect of this event helps to explain a portion of this massive height; however, the rest must be attributed to a local submarine landslide. In Hilo alone, 96 people died, The residents of these islands were caught off-guard by the onset of the tsunami due to the inability to transmit warnings from the destroyed posts at Scotch Cap, and the tsunami is known as the April Fools' Day Tsunami in Hawaii because it happened on April 1. The effects of the tsunami also reached Washington, Oregon, and California. The large-scale destruction prompted the creation of the Seismic Sea Wave Warning System, which became known as the Pacific Tsunami Warning Center in 1965. ==See also==