Earthquake News

Magnitude 8.2 Earthquake Offshore of Alaska Peninsula, the Biggest Earthquake Recorded in 50 Years


The strongest earthquake to hit the United States in fifty years struck off the coast of Alaska on July 28 at 10:15 p.m. Alaska time. A medium-depth earthquake, the Chignik Earthquake measured around 28.5 miles deep.

The M7.6 Simeonof Island Earthquake, which erupted on July 21, 2020, was located around 45 miles from the Chignik Earthquake's location. Although the Chignik Earthquake was the deepest of the two, they both occurred along the boundary between the Pacific plate that was subducting and the North American plate that was superimposing. There are thousands of earthquakes per year in the seismically active Alaska Peninsula. The interface, also known as the Aleutian megathrust, is where the greatest earthquakes occur. This interface between the Shumagin Islands in the southwest and Kodiak Island in the northeast was ruptured by the M8.2 event. This portion of the interface was already fractured by the 1938 M8.3 earthquake.

Alaskan Earthquake

The two communities that experienced the most intense shaking during the Chignik Earthquake were Perryville and Chignik, which were closest to the epicenter. Additionally, there were numerous felt reports from locations around Alaska, even from as far away as the Mat-Su Valley in Southcentral Alaska. The aftershock rate has been active thus far, so locals may continue to experience trembling. A M6.1 aftershock occurred roughly four minutes after the mainshock at the time this report was written.

The National Tsunami Warning Center issued a tsunami warning for much of coastal Alaska because to the offshore location. Evacuations were ordered by several localities. However, the measured wave heights were less than a foot, and a few hours after the incident the warning was lowered.


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