Alaska Peninsula and Aleutian Island Seismicity

By far the largest earthquakes in the state occur on the megathrust zone, caused by subduction of the Pacific Plate beneath Alaska, extending westward from Prince William Sound along the Alaska Peninsula and Aleutian Islands. Two of the seven largest earthquakes of this past century have occurred in the Aleutian Islands (1957 Aleutian M8.6 and 1965 Rat Islands M8.7). The hazards associated with these events are enormous and areas as large as the entire state of California are affected. Although it is generally believed that these great earthquakes are rare, with recurrence times on the order of a few decades to hundreds of years for an individual segment, five great underthrusting events have occurred in Alaska since 1938.

The entirety of the Aleutian Islands is composed of complex tectonic collisions, and rectangular blocks contained within shear zones and deforming canyons. It is in this environment that the largest earthquakes occur, spawning some of the most destructive tsunamis.

Quick Links to Interactive Seismicity Maps

Interior Alaska
Southeast Alaska
South Central Alaska
Aleutian Islands and Alaska Peninsula
Northern Alaska
Western Alaska


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Updated: October 2006