On June 14, 2005, a series of moderate to strong earthquakes occurred in the Rat Islands region of the Aleutian Islands (red stars on the above map). The sequence started with a M5.2 event at 08:03 UTC and the largest event of M6.8 followed 9 hours later (at 17:10 UTC). The largest earthquake was situated 49 kilometers (31 miles) south-southeast of Amchitka. The epicenter (largest star) was located at 51.31N and 179.41E at 51.7 km depth. This earthquake is the largest to occur in this region since the magnitude 7.7 event on November 17, 2003 (white star on the map). The AEIC located several foreshocks and aftershocks of the M6.8 event with the largest aftershock of M5.6 four and a half hours after the main shock. This page will be updated as more aftershocks are located. 

The M 6.8 earthquake occurred on the convergent boundary between the subducting Pacific and overriding North American crustal plates. This region, where the two plates are being forced directly into one another, is one of the world's most active seismic zones. Over one hundred earthquakes of magnitude seven or larger have occurred along this boundary in the past hundred years. A separate map illustrates the recent earthquakes as circles, superimposed on stippled areas illustrating the rupture zones of major earthquakes. Generally speaking, the magnitude of an earthquake is roughly proportional to the area involved in its faulting. Each major rupture is labelled with the earthquake's year and a black dot indicating the epicenter for the associated earthquake. With the exception of the Unalaska and Shumagin seismic gaps, all portions of this plate boundary have ruptured within the past hundred years.

The 1965 Mw 8.7 Rat Islands earthquake ruptured a ~600 km-long portion of the plate boundary to the west of the Amchitka Island (see map). In November 17, 2003 M7.7 earthquake, the easternmost part of the 1965 zone failed again. The current sequence of earthquakes is located east of the 2003 rupture zone, at the easternmost end of the 1965 rupture zone. The 1957 M8.6 earthquake ruptured segment of the meguthrust east of the 1965 zone. A M7.9 event in 1996 and a M8.0 event in 1986 re-ruptured the western segment of the 1957 fault zone.