An earthquake of magnitude 6.4 (M6.4) which struck off the coast of Alaska on 12 November 2012 did not trigger a tsunami, and no damage has been reported – despite the size of the quake.
The earthquake occurred some distance from shore, approximately 500km from Juneau and 550km from Anchorage, at a depth of around 55 km.
A number of smaller foreshocks and aftershocks were also recorded.
Tectonic Setting of Alaska
Alaska is at the north-eastern point of the seismically-active belt surrounding the Pacific Ocean known as the Pacific Ring of Fire.
To the south, the Queen Charlotte Fault forms a transform boundary characterised by lateral movement, while to the west the Pacific Plate is subducted beneath the North American Plate in what is known as the Aleutian megathrust – a zone characterised not only by frequent earthquakes but also by a major arc of volcanic islands.
The earthquake of November 12 occurred just between these two zones, at a point where a small sliver of crust is being subducted beneath the North American continent at a rate of around 5cm per year. We see large earthquakes in the area, and all throughout central Alaska as a result of this movement.
The complex tectonic setting of this area also causes a number of major faults within the North American Plate lying broadly parallel to the boundary: these are also subject to frequent seismic activity and include the Denali, Kaltag and Castle Mountain faults.