M 7.0 - 101 km SW of Atka, Alaska

Tectonic Summary

The August 30, 2013, M 7.0 earthquake southeast of Adak, Alaska, occurred as the result of shallow thrust faulting on or near the subduction zone interface between the Pacific and North America plates. At the location of this event, the Pacific plate moves towards the northwest relative to the North America plate at a velocity of about 73 mm/yr, beginning its descent into the mantle at the Aleutian Trench approximately 130 km south of the August 30th earthquake. The depth and mechanism of this earthquake are consistent with it occurring along the megathrust interface between these two plates.

The Aleutians Arc has frequent large earthquakes; two dozen events of M 6.5+ have occurred over the last century within 250 km of the August 30th earthquake. The largest of these was a M 8.6 earthquake in March 1957, whose hypocenter was located just 15 km south of the August 30th earthquake. Aftershocks associated with the 1957 event extended for more than 1,000 km along the arc, roughly from the International Date Line in the west to Unimak Island in the east. The 1957 earthquake also resulted in a large tsunami that was observed throughout the Pacific Basin, and caused damage locally along the Aleutian Arc and in Hawaii. Other large nearby events include the May 1986 M 8.0 earthquake 40 km to the southeast, and the June 1996 M 7.9 earthquake 150 km to the west. Neither of these more recent events is known to have caused fatalities or significant damage.

Hayes et al. (2016) Tectonic summaries of magnitude 7 and greater earthquakes from 2000 to 2015, USGS Open-File Report 2016-1192. (5.2 MB PDF)