Officials say they have received no reports of the earthquake being felt or causing any damage.
The epicenter is believed to be more than 140 miles southwest of Dutch Harbor and Unalaska.
Seismologist Natasha Ruppert with the Alaska Earthquake Information Center says the earthquake was an aftershock to a 6.6- magnitude quake that occurred July 17 in the same area. That earthquake, originally estimated at a 6.7 - magnitude, has been downgraded slightly.
Ruppert says the Fox Islands have been very active with aftershocks. No one has been injured and no damage has been reported.
Ruppert says the aftershock activity is unusual in that there have been so many of them. She says each aftershock can produce its own aftershocks.
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