The earthquake was recorded at 07:52 GMT on Friday. The epicentre was located 157 kilometres to the east of the city of Gold Beach on the Oregon coast, at a depth of 9.1 kilometres.
No injuries or casualties have been reported so far.
Less than 25 minutes later, a second 5.9-magnitude earthquake hit nearby, almost 143 kilometres to the east of the city of Gold Beach, at a depth of 14.5 kilometres.