AN EARTHQUAKE has struck California waking thousands around Berkeley and San Jose with San Francisco Bay Area locals fearing the Big One bracing for aftershocks.
The earthquake is believed to have struck just 3km from Berkeley, and some 65 km northwest of San Jose, shortly before 3am local time (10am UK).
The "strong" tremor woke thousands of people up as many took to social media in fear of it being the "Big One".
One tweeted: "Wow! Just experienced a major earthquake in San Jose, California. Brace for after shocks..."
Another wrote: "Omg, the earthquake scared me! So unexpected and different from others."
And one said: "There was an earthquake just now and i was fully expecting it to be the big one that destroys California".
The quake apparently woke people in the Bay Area and was felt in San Francisco, Oakland, Walnut Creek and as far away as Dublin, Livermore, Union City and Milpitas.
Reports indicate the earthquake - 18km from San Francisco - was felt throughout the region for around five to 10 seconds.
Several jolts were felt at San Francisco International Airport and the US Geological Survey website says people reported feeling the quake 40 miles (64 kilometers) south in San Jose.
One Twitter user posted: "California, you need to chill out. I was not looking to be woken up by your 4.7 mag earthquake."
Another added: "Still freaking out. All through my childhood, I lived through hurricanes but you always knew when they were coming. It's terrifying not knowing when an earthquake will strike or how strong it will be. This 4.5 earthquake was a whopper."
Resident Edwin Antonio Coreas Renderos posted on Facebook: "I'm right by Laguna Honda Hospital here in [San Francisco] and I'm on the 9th floor of my building and it was pretty scary how long the shaking lasted.”
Gina Solis posted on the CBS San Francisco Facebook page that it rocked her home in San Rafael, saying: "It shook our house and shook the bed big time!!!"
One person in San Francisco said the earthquake was strong enough to knock picture frames from the wall.
However according to the USGS, the quake was recorded at around 4.4 magnitude - which is not expected to cause major damage.
It was originally reported by the United States Geological Survey as a 4.7 magnitude earthquake, then quickly revised down.
USGS seismologist Robert Sanders said “there’s always a possibility of some minor damage to older structures in the area.”
An earthquake of this size also typically produces after shocks, leaving Berkeley and San Jose citizens fearing damage could come later.
The San Francisco Department of Emergency Management says there is no threat of Tsunami at this time.
The epicentre of the earthquake was recorded in the area of the Hayward fault, one of the most feared in the Bay Area, which could produce a magnitude 7 or greater earthquake and is directly underneath heavily populated areas.
Today's latest quake will now spark fresh fears "The Big One" – an "inevitable" magnitude 7.0 earthquake or greater – is imminent.
In 2008, the US Geological Survey found there was a 99% chance of a huge quake hitting California, which sits on the San Andreas fault which is part of the "Ring of Fire".
A report warned a huge quake of this size could kill 1,800 people, injure 53,000, and cause $214billion (£162billion) of damage.
It comes a day after a 2.9 magnitude quake struck Cambria in California, and two days after a 3.0 magnitude tremor struck Aromas.
On New Year’s Day, a 6.0 magnitude quake hit Ontario - the largest in the region so far this year.
The Bay Area was also seismically active at the end of 2017, as a cluster of about 30 earthquakes was recorded by the USGS in the last few days of December.
The largest was a 3.9-magnitude on Dec. 26 near Alum Rock in San Jose.
San Francisco - where residents live with the constant threat of tremors - is no stranger to earthquakes.
A devastating 7.8-magnitude quake in 1906 killed an estimated 3,000 people and levelled the city with its powerful tremors.
Another measured at 6.9 killed 63 and injured 3,757 people and damaged countless buildings in 1989.