2007 M6.4 Fox Islands Earthquake

Mainshock and Aftershocks: 

The Alaska Earthquake Center located a strong earthquake that occurred on Wednesday, December 26, 2007 at 1:04 pm AKST (22:04 pm UTC) in the Fox Islands region of Alaska (red star on the above map). We located over 160 aftershocks through the end of the month (magnitudes 2 and greater, white circles). The largest aftershock, of magnitude 5.0, occurred on December 29 at 1:57 pm AKST (22:57 pm UTC).

Tectonic Setting: 

 The 1957 Mw 8.6 Andreanof Islands earthquake ruptured a ~600 km-long portion of the plate boundary in central Aleutian Islands. The current sequence of earthquakes is located within the eastern segment of the 1957 rupture zone.

This is the largest event to occur in the region since the M6.4 earthquake on May 10, 2006 (yellow star). The December 26 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 labeled 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.