When the Big One came, it was with more of a whimper than a bang. A distant rumble was followed by a man calmly telling his 5 million listeners to "drop, cover and hold on". The rumbling turned to tinkling as windows shattered and glass fell.

Across southern California, children giggled and adults discovered the allure of sharing floor space with strangers.

Yesterday's drill, the Great Southern California ShakeOut, had been billed as the nation's largest ever, priming residents of the area most vulnerable to the Big One.

"It's what we call a teachable moment," said Douglas Yule, a California State University Northridge geology professor, who led his students from their classes to gather on the central plaza in the campus.

"The point of this exercise is to get people to take it seriously," he told his audience of around 100. "Don't just shrug it off. Put some water in your garage. Have a pair of shoes under your bed. What's going to happen is that it goes third world for a while, no water, no power. Who remembers '94?"

The Northridge earthquake in 1994 was the last big to shake southern California, leaving 57 dead, buckling freeways and causing an estimated $20bn in damage.

One of the epicentres was the spot where Yule was addressing his students. Across the plaza stands a monument to those who worked to reopen the campus.

Dave Liggett, now a geology technician at the university, remembers the 1994 quake as a bonding experience. "The house shook pretty good," he said. "The biggest mess was the pancake syrup. People in my neighbourhood are pretty independent. For many, the first time you met your neighbour was on that morning."

The Northridge quake was a 6.7 magnitude tremor; Thursday's drill was based on something far more fearsome, a 7.8, 200-mile-long shock spreading along the southern San Andreas fault from the desert near San Diego to Los Angeles. A model developed by the US Geological Service envisages 1,800 deaths, 50,000 injuries and $200bn in damage. Fifteen million people in southern California could be left for weeks without power, and months without water.

An earthquake of a similar magnitude to the drill takes place every 150 years on the southern San Andreas fault. The last one was 151 years ago and scientists warn that the fault is "10 months pregnant".

"In '94 this campus was devastated by an earthquake that lasted 10-15 seconds," Yule said. The model for the next Big One assumes tremors lasting three minutes.

The Chino Hills earthquake this summer delivered a 5.4 magnitude shock to an area 30 miles east of Los Angeles. But the biggest motivator behind the ShakeOut was Hurricane Katrina in 2005.

But with preparation, Yule declared, there could be an upside to the Big One. "We're all going to suffer," he said. "But with some preparation it can be looked on as a great adventure, something you can tell your kids about."