1996 M7.9 Adak Earthquake

Earthquakes in the Adak area occur on the convergent boundary between the Pacific and 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.

The 1957 Andreanof Islands Mw 8.6 earthquake ruptured an 800 km-long portion of the plate boundary; in 1986 a portion of the western half of this 1957 zone failed again in an earthquake of magnitude 8.0. The 1996 earthquakes appear to have completed re-rupture of the western end of the 1957 zone, immediately westward of the 1986 region.

The Harvard centroid moment tensor solution indicates a thrusting mechanism on a north-northwest dipping plane consistent with the regional tectonics. Moment tensor solutions for the aftershocks are similar to the main shock.