Rat Islands
The Aleutian Islands are a volcanic arc lying above the convergent boundary where the Pacific Plate is being subducted beneath the North American Plate. Earthquakes in the area are caused by movement along the plate interface (such as the 1965 Rat Islands earthquake), normal faulting within the outer rise and within the subducting slab. The earthquake's epicenter lies close to a major break in the Aleutian chain, between the Andreanof Islands to the east and the Rat Islands to the west, along what is known as the Amchitka channel. In this region there is evidence for a tear in the lithosphere of the descending slab. It is thought that this tear is caused by the unusually sharp curvature of this part of the arc coupled with the interaction of Bowers Ridge in the over-riding plate with the subduction zone.