One of the most powerful earthquakes to hit California in recent years has affected an area stretching from Los Angeles to San Francisco.
Some buildings collapsed, causing death and damage
Two women died when a 19th Century clock tower collapsed in the worst-hit town of Paso Robles, 300km north of LA.
Power supplies to about 40,000 people were cut and more than 80 buildings were damaged in the quake, which had a magnitude of 6.5.
The earthquake was followed by dozens of aftershocks.
California is one of the most quake-prone regions of the world, being criss-crossed by the San Andreas Fault System.
The latest quake is thought to have struck the San Simeon fault, parallel to the San Andreas Fault that runs the length of California.
'Whole town shook'
The women, one aged 55 and the other aged 19, were killed by falling debris when Paso Robles' clock tower collapsed.
"We have reports of two deaths attributed to the quake and have no reason to believe that anyone is still trapped in the building that collapsed," said California Highway Patrol spokesman Office Scott Lee.
Earlier, authorities had said that three people were believed dead.
"The whole town shook and the building came down. It was horrible," said hotel worker Brandy Wilson.
Paso Robles suffered extensive damage, with buildings more than a century old bearing the brunt of the damage.
The historic clock tower in Paso Robles was destroyed
Built in the 1880s, they were made of brick and wood and had not been reinforced to protect them from earthquakes, says the BBC's Peter Bowes in California.
The quake also struck a tourist area in the town of San Simeon, shaking the castle of US press baron William Randolph Hearst. The building is reported to have suffered no structural damage.
Tad Weber, managing editor of The Tribune in San Luis Obispo, said he was in a meeting when it struck.
"All of a sudden there was a jolting and we look up and see the building swaying," he told the Associated Press. "I dived under a desk to wait it out."
There were reports of some people injured at a winery in the area.
Superintendent Pamela Martens, of the Coast Unified School District in Cambria, in the county of San Luis Obispo, said the school was closed for the holidays, but the quake had left "things off the shelf and all over the place. Computers are down."
Our correspondent says people in Cambria, close to the epicentre, were amazed to find their homes still intact.
A spokesman for the US Geological Survey told reporters: "We have a typical 6.5 magnitude earthquake that fortunately has occurred far from densely populated areas."
He said a similar-sized earthquake located under a city such as Los Angeles could have caused billions of dollars worth of damage.
The spokesman said the earthquake had triggered a vigorous system of smaller aftershocks, but there was nothing to suggest a bigger quake was imminent.
But he said the chances of the region experiencing a bigger earthquake in the future were now higher than before the latest earthquake struck.
Earthquakes in California are not uncommon. The Northridge Earthquake in Los Angeles in 1994 measured 6.7 and left 57 people dead and 1,500 people were injured.
The latest earthquake was the most powerful in California since a 7.1 quake struck the desert near Joshua Tree more than four years ago.
The San Andreas fault marks the boundary between two great land masses that are slowly moving in opposite directions - the Pacific tectonic plate on the west and the North American plate on the east.
As the plates grind against one another, earthquakes are triggered along the fault.
I live only a two hour drive from the epicenter (Santa Barbara) and the quake was my first since moving to California only 2 1/2 years ago. It was very exciting to "feel the earth move" as Carly Simon sang "whenever you're around." I wanted a cigarette afterwards! Thankfully it was not devastating for many.
Mark Walker, USA
I was working in my office when a co-worker started yelling my name, I found it odd that she didn't use the intercom, so i yelled back I'll be right there(i was filling some paperwork) then i walked into her office room and she asked me if i felt the earthquake, at first i thought she was kidding, but then she showed me the blinds that were shaking back and forth! My neighbour was on the WTC in Long Beach, 19th floor, they all left the building many feeling seasick after the building swayed back and forth.
Sam Awad, Canadian in LA
I was on the 15th floor of an office building in Los Angeles. The whole building was swaying for at least a couple of minutes. Some people ran for the exits, most just stayed put and were left feeling sea sick.
Naomi, USA (formerly UK)
Working in a business which large container trucks visit frequently, I at first thought that the low rumbling was simply a truck driving by; however, my co-worker quickly called the swinging window blinds and lights to my attention. We searched the internet and quickly found out that there had been a 6.5 earthquake. While it was not severe here, it was still amazing, as this was my first earthquake!
Darcy Cooper, Pleasanton, CA USA
The house moved energetically, mains power was off for several hours. Watching the porch pillars shift back and forth through the window, I was surprised that there was no extensive damage. Drawers and doors opened, unsecured tall items toppled, animals were upset. Here it was less of a roll and more of a back and forth shake. Close to the epicenter, my mother experienced a rolling motion, with the sensation that floor dropped out from beneath her. She also had a lot of broken glass and china, and a large bronze statue beside the fireplace, ended up several feet across the room.
Joanne, Brit in the US
I was at work in Los Angeles on the 5th floor of my building, we had a lot of swaying that actually made one feel quite sea sick, some people ran out of the building, we stayed put, being terribly British I didn't like to make a fuss and overreact! This is the second earthquake I've experienced and they were both very different, this was a silent roller, the last one was a very noisy violent jerking.
Kerstin, British ex-pat, Los Angeles
Roughly 200 miles north east of the quake. Two friends at work asked if I'd felt the quake. I said I hadn't. The interesting thing is that they are on the fourth floor of our building and had felt the building sway. I on the ground floor felt nothing. It all depends on where you are sometimes whether you feel a quake.
Michael, San Ramon California USA
I'm from California but have moved to England as I've married an Englishman. I just spoke with my family in California and they we're shaken up when it hit. When I lived there I moved on my sailboat because I just found when the Earth moved under my feet it was simply to terrifying! I'm really happy to be here in England!
Julia Smethurst, England
The quake was felt here 50 miles north of LA. Everyone in the factory here calmly left the building.
Bob Thomas, usa
I was driving along the Pacific Coast Highway near Santa Barbara when my 4WD started swaying, as if caught in a gale. I looked at the ocean, which was calm and showed no sign of high winds, and then at the trees at the side of the road, their branches were not moving. I didn't realise there had been a 'quake until I arrived in Santa Barbara for a meeting and I saw people standing in the middle of the roads, away from buildings and trees. I experienced the last big 'quake four years ago, I'd just bought a small cabin in the mountains and it hit during my first night there. This latest 'quake was a "roller", it feels as if one is on a small boat.
Dave Rubin, USA
I have only just come back from San Francisco, but my brother lives there and he said he felt the house shake.