A strong earthquake measuring 8.2 on the Richter Scale struck 300-km south-east of Kodiak, Alaska at a depth of 10-km on Tuesday.
The United States Geological Survey said a tsunami alert has been issued and the U.S. west coast and Hawaii are under the watch.
The NWS Pacific Tsunami Warning Center said that, based on the preliminary earthquake parameters, "widespread hazardous tsunami waves were possible".
People in the affected areas are being told to seek refuge on higher grounds.
However, there are no reports of damage so far.