Earthquake in Alaska: M6.4 Quake Strikes November 12, 2012


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Alaska Earthquake: Big quake, little damage, November 2012 – Image Credit USGS

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.

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