Los Angeles has been shaken by a pre-dawn earthquake with a magnitude of 4.4 that jangled nerves in the West Coast but caused no major damage or casualties.
Car and burglar alarms went off and a few objects fell off shelves after the tremor, which struck just before dawn with its epicentre about 32km northwest of Los Angeles, at a depth of only five miles.
It was the most significant shaking caused by an earthquake in southern California since one with a magnitude of 5.5 in 2008.
"I woke up to feel the building swaying from side to side," Wes Lashley told KCAL 9 news, while local resident Mary Lyon added: "It felt like a 5.9 or 6 to me."
The quake was initially estimated as a magnitude 4.7 by the US Geological Survey (USGS), but later downgraded it to 4.4.
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But it felt stronger to many Angelenos. One AFP reporter in the Hollywood neighbourhood said several objects fell off shelves.
Morning news anchors on the local KTLA television station dived under their desk as the quake visibly shook the studio around them.
No disruption was reported at the city's LAX airport, although Metro trains were delayed as engineers checked tracks for damage, officials said.
USGS seismologist Robert Graves said small aftershocks would likely continue for a few days, while there was a five per cent chance that the quake was a forerunner to a larger earthquake.
"This is a reminder that we live in earthquake country here in southern California," he told reporters.
The quake came a week after a powerful 6.9-magnitude earthquake struck off the coast of northern California, the biggest in years.
California has long braced for the "Big One."
Geologists say a quake capable of causing widespread destruction is 99 per cent certain of hitting California in the next 30 years.
