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The Aleutian megathrust, where the Pacific tectonic plate is being forced underneath the North American plate, is one of the world's most active seismic zones. During the previous ten years, the region experienced an average of two magnitude 6 or greater events per year.

The August 15 earthquake occurred in the outer rise area of the Aleutian trench. The waveform radiation pattern indicates normal faulting which is typical for the outer rise events. This event originated inside the subducting Pacific plate and is result of the plate bending as it enters the mantle. It was located updip of the rupture zone of the 1957 M8.6 Andreanof Islands earthquake.

Last Modified: May 14, 2020