A 6.5 magnitude earthquake has been reported off the coast of northern California, the United States Geological Survey has said.

The epicentre was 165km west of Ferndale, California, at a shallow depth of 10km, according to the scientific agency.

The quake – which hit around 6.50am Pacific time – was initially thought to be 6.9-magnitude, but the it was revised down to 6.5.

There was no tsunami warning, advisory or threat in effect following the earthquake, the Pacific Tsunami Warning Center of the National Weather Service said on its website.

Some social media users said they felt the tremor in San Francisco, about 418.43 km south.

"That was a big one," wrote Twitter user Antonis Papatsaras from the Bay Area city.

"Felt 20 seconds of very light shaking," tweeted another San Francisco resident, Lila LaHodd.

Two quakes exceeding 4.0-magnitude have shaken California in the last week

On Wednesday a 6.5-magnitude quake in Indonesia killed more than 100 people.