Interior Alaska Seismicity

The tectonic framework of Alaska is dominated by subduction of the Pacific plate underneath the North American plate. Stresses due to the plate convergence are transmitted across great distances (>500 km) into interior Alaska where the deformation causes substantial crustal seismicity. While some of the earthquakes are clearly associated with the large-scale strike-slip fault systems of the Denali in the south and Kaltag and Tintina in the north, the majority of the shocks are located in a zone of distributed shear deformation between the two fault systems. These earthquakes are aligned in three major north-northeast trending zones which are called Minto Flats (MFSZ), Fairbanks (FSZ), and Salcha (SSZ) seismic zones. Little is known about the geological structures that produce this broadly distributed seismicity. It has been proposed that the crustal seismicity in interior Alaska between the Denali and Kaltag fault systems is caused by crustal block rotations. The crustal blocks rotate clockwise is a shear zone between the two fault systems in response to the compressive stresses transmitted from the plate convergence boundary in southern Alaska. Substantial subduction zone seismicity is also present in interior Alaska.

Among the largest earthquakes in the interior are the 1904 Ms 7.3, 1929 Ms 6.2 and 6.5, 1937 Ms 7.3, 1947 Ms 7.2, and 1968 Ms 6.5 Rampart earthquakes. Locations for the three earlier shocks are rather uncertain, but can be generally identified with the areas between the Denali and Tintina fault systems. The most recent events of note are the 2002 M6.7 and M7.9 Denali Fault earthquakes.

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