![]() In 1971, the Shumagin segment drew the attention of seismologists as it was proposed as a seismic gap because no major seismic activity have occurred in recent times. This segment lies between the Unimak and Semidi segments which had ruptured in earthquakes in 19 respectively. South of the Alaska Peninsula is a segment of the Aleutian subduction zone known as the Shumagin segment, named after the nearby Shumagin Islands. This megathrust fault has been the source of many large earthquakes including the 1964 Alaskan earthquake that registered a magnitude 9.2 and remains the second largest earthquake in recorded history. Off the coast of Alaska lies the Aleutian subduction zone–a 2,500 mile long convergent plate boundary where the Pacific Plate subducts under the North American Plate at a rate of 6–7 cm/yr. A tsunami warning was rescinded and no large waves were observed because the earthquake took place 32 km beneath the seafloor deep enough that vertical uplift of the seafloor was limited therefore displacing smaller amounts of water. The limited impact from this earthquake was attributed to it occurring offshore from the sparsely-populated Alaska Peninsula. In Perryville, the closest populated area to the quake, cracks appeared in drywalls and on the ground. No casualties or serious damage were reported in the aftermath of the mainshock, as well as some of the strong aftershocks. It was also the strongest earthquake globally since the 2015 Illapel earthquake, tying the 2017 Chiapas earthquake and 2018 Fiji earthquake. This was the largest earthquake in the United States since the 1965 Rat Islands earthquake, and the 7th largest earthquake in US history. The mainshock was followed by a number of aftershocks, including three that were of magnitude 5.9, 6.1 and 6.9 respectively. A tsunami warning was issued by the National Oceanic and Atmospheric Administration (NOAA) but later cancelled. The large megathrust earthquake had a moment magnitude ( M w) of 8.2 according to the United States Geological Survey (USGS). The cookie is set by the GDPR Cookie Consent plugin and is used to store whether or not user has consented to the use of cookies. The cookie is used to store the user consent for the cookies in the category "Performance". This cookie is set by GDPR Cookie Consent plugin. The cookie is used to store the user consent for the cookies in the category "Other. The cookies is used to store the user consent for the cookies in the category "Necessary". The cookie is set by GDPR cookie consent to record the user consent for the cookies in the category "Functional". The cookie is used to store the user consent for the cookies in the category "Analytics". ![]() These cookies ensure basic functionalities and security features of the website, anonymously. Necessary cookies are absolutely essential for the website to function properly. Contact us and we’ll set up a trial account for you. Sign up for a trial account and access full impact reports of all events.
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