Experts believe another huge earthquake in California is inevitable
About five million people in California have taken part in the biggest earthquake drill in US history.
Schools, hospitals and staff working in public buildings all responded to the simulated tremor at exactly the same time.
Children donned fake blood to act as victims, while fire-fighters with chainsaws and rescue gear rushed to the scene of a burning building with artificial smoke billowing from its windows.
The drill was designed to alert people in the state to the threat of a potentially catastrophic earthquake. Scientists believe a quake with a magnitude of at least 7.0 will happen within the next 30 years.
The locals, the state and the federal government came together very quickly, unlike what we have seen at [Hurricane] Katrina
"I think it is extraordinarily important for California," says Dr Lucy Jones, a seismologist with the US Geological Survey (USGS).
"It's been 15 years since we really had a damaging earthquake in LA and it's very easy for people to forget over that sort of time what things were like," she adds.
"This is a chance to really look at what it means to have this many people involved in the disaster and the stretch of resources that it's going to entail."
'Drop, Cover and Hold On'
At exactly 1000 (1800 GMT), local radio stations and public address systems in schools and hospitals alerted people to a simulated 7.8-magnitude quake.
Reaction to the quake drill in California
Pupils responded immediately by diving under their desks for cover.
They stayed in place for two minutes, which is the estimated duration of a quake of this magnitude. During this time buildings would shake violently.
The "Drop, Cover and Hold On" drill is a well-rehearsed routine at California schools.
Kelli Clarke, a teacher at Robert Louis Stevenson Elementary School in Burbank, said her class of nine-year olds responded well.
"They did exactly what they'd been trained to do and what they'd been practising doing and they did a good job."
If a quake of this magnitude were to happen, the authorities say 1,500 buildings would be destroyed, there would be 1,800 deaths and $200bn (£135bn) in damage.
In addition, major roads would collapse, water and gas pipes would burst and power lines would go down.
The imagined earthquake would, officials say, cause 2,000 deaths
"What life is going to be like in Southern California after this event is really going to depend on the choices we've made before this event," says Dr Jones.
"To retrofit or not, to store water, how quickly we can get the economy up and running will determine whether this is a disaster or a catastrophe."
The mock earthquake was in a section of the San Andreas fault that has not moved in more than three centuries. Scientists fear a build-up of pressure could unleash a huge quake in the near future.
California's governor, Arnold Schwarzenegger, praised local and federal agencies for co-ordinating the drill.
"The locals, the state and the federal government came together very quickly, unlike what we have seen at [Hurricane] Katrina, when it was going the other way," he said.
Dr Jones adds: "We've gotten people to see others taking action and that'll help encourage them to take action themselves."
"We need enough people in Southern California to have decided to do their part to keep the social system working after the event."
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The locals, the state and the federal government came together very quickly, unlike what we have seen at [Hurricane] Katrina
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