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 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. Warning sirens sound in Kodiak, Alaska, after an earthquake off the coast Saturday. “Great” earthquakes are registered at magnitude eight or larger, and Alaska has one on average every 13 years.Īccording 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. The quake initially was reported as 7.4 magnitude but downgraded to 7.2 soon after. west coast six hours after the quake.Īlaska is one of the most seismically active areas in the world, according to the state’s government website. 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. The USGS is estimating that little to no damage will be caused by the actual quake. agencies are sending out emergency alerts via Twitter. The largest was a magnitude 5.9, eight minutes after the magnitude 8.2. The large megathrust earthquake had a moment magnitude (M w) of 8.2 according to the United States Geological Survey (USGS). The warning was prompted after a large 7.9 magnitude earthquake was detected in the Gulf of Alaska in the early morning hours.īoth Canada and U.S. The Alaska Earthquake Center reported 14 aftershocks of magnitude 4 or larger in the first two hours after the quake. An earthquake occurred off the coast of the Alaska Peninsula on July 28, 2021, at 10:15 p.m. Anyone in the vicinity is advised to move inland, find higher ground, and help others who may not be able to escape unaided.Ī tsunami watch was also in effect for Washington, Oregon, and California. In 1912, a series of M7+ earthquakes was associated with the Novarupta eruption, which was the largest volcanic eruption of the 20th century worldwide.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.Įarly this morning, a tsunami warning was issued and within three hours cancelled for the west part of Canada and coastal Alaska. (3) Crustal seismicity in this region can be attributed to the Kodiak Shelf Fault Zone and to the volcanic arc. In 2016, the magnitude 7.1 Iniskin earthquake had brought Southcentral’s. It was the second time in three years that an early morning January earthquake woke Alaskans across the state. Both earthquakes caused damage and disruption to the City of Kodiak and other communities on the island. At 12:31am on January 23, a magnitude 7.9 earthquake struck in the Gulf of Alaska about 180 miles southeast of Kodiak Island (see figure 1). The most notable examples of such earthquakes are the 1999 M7.0 and the 2001 M6.9 Kodiak Island events. The Aleutian-Alaska Wadati-Benioff Zone produces thousands of earthquakes each year, most of which are too deep and too small to be felt. In the Alaska Peninsula region, the seismicity abates at approximately 150 miles (241 km) depth, reflecting the down-dip extension of the Pacific Plate. This zone extends along the Aleutian Arc, Alaska Peninsula, and Cook Inlet. (2) Intermediate depth seismicity (below 20 miles/32 km) occurs in the Wadati-Benioff Zone, where the subducting Pacific Plate descends towards the mantle beneath the North American Plate. A 7.2 magnitude earthquake triggered a brief tsunami advisory for southern Alaska late Saturday, but the advisory was canceled about an hour later, monitoring bodies reported. While these recent earthquakes did not produce damaging tsunamis, previous tsunamis were documented in historical records of Russian communities and in recently discovered paleo-tsunami deposits. The most recent examples include the 2020 M7.8 Simeonof Earthquake under the Shumagin Islands and the 2021 M8.2 Chignik Earthquake southwest of Kodiak Island. Tectonic Setting of the Alaska PeninsulaSeismicity in the Alaska Peninsula region is produced by different tectonic features: (1) The Aleutian megathrust is the source of the strongest earthquakes in the region.
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