The earthquake was recorded at 6.12 UTC. The epicentre of the tremors was located 98 kilometres south of the town of Perryville.
The seismic activity was recorded at a depth of 10 kilometres.
A tsunami warning has been issued by the authorities.
The video published on social media shows sirens wailing amid a tsunami warning.
#BREAKING: Strong 7.8 quake hits off Alaska; tsunami warnings issued— The Coronavirus Gazette (@COVIDGazette) July 22, 2020
Video below shows sirens wail as a tsunami warning is issued in Alaska following a massive 7.8 quake
No information about casualties and destruction has been reported.