Current location estimate of magnitude~8 offshore Alaska earthquake 10 mins ago seems to indicate that it occurred within the oceanic Pacific plate before it subducts at the trench. Possibly a normal faulting event? Significant tsunami risk. pic.twitter.com/G5BL1HwLi3— Stephen Hicks (@seismo_steve) January 23, 2018
If Alaskans weren’t jolted awake by the magnitude 7.9 earthquake of their coast this morning, the ensuing tsunami warning sirens likely stirred them.
Early this morning, a tsunami warning was issued and within three hours cancelled for the west part of Canada and coastal Alaska. Anyone in the vicinity is advised to move inland, find higher ground, and help others who may not be able to escape unaided.
A tsunami watch was also in effect for Washington, Oregon, and California. The warning was prompted after a large 7.9 magnitude earthquake was detected in the Gulf of Alaska in the early morning hours.
The USGS is estimating that little to no damage will be caused by the actual quake. According to the U.S. Tsunami Warning Center, Canada’s coastal regions are most likely to see waves three hours after the quake hit, and could hit the U.S. west coast six hours after the quake.
Alaska is one of the most seismically active areas in the world, according to the state’s government website. “Great” earthquakes are registered at magnitude eight or larger, and Alaska has one on average every 13 years.
According to the state’s data, more than 1,000 earthquakes of varying magnitudes are detected in the large area the size of half the continental U.S. every month.
The Gulf of Alaska sits at the boundary of two large tectonic plates—the land mass sits over the North American plate, while coastal areas are over the Pacific plate. These two plates form a subduction zone where the latter plate is being constantly forced under the former, creating an intense amount of friction that causes earthquakes when released.
The 1964 earthquake that struck Alaska is still remembered as one of the most devastating in history. It struck on Good Friday, branding it the Good Friday Earthquake. The 9.2 quake was caused by the Pacific plate jolting under the North American plate. It was the second largest quake ever recorded in the world.
National Geographic covered the devastation in 1964. (The full feature is behind our paywall. Subscribers can read it here.) Residents recount being violently thrown to the ground, seeing the ground seemingly tear apart, and watching their own homes collapse.