Apocalypse - but not right now. How California stays cool about the Big One

It's been a good week for Lucy Jones. On Tuesday, the chief scientist at the US Geological Survey in Pasadena, California, got what she had been waiting for: an earthquake rumbled through Chino Hills, some 40 miles east of Los Angeles.

But this was not the fabled Big One, star of movies, protagonist of novels and mover of mountains. Rather, the Chino Hills quake registered a magnitude of just 5.4, enough to shake some sets in Hollywood, rupture a few water mains and trigger a stampede from an office building causing five injuries in LA's glitzy Wilshire Boulevard.

"It was by all counts a moderate earthquake," said Yuri Fialko, a geophysicist at the Scripps Institution of Oceanography in La Jolla, California, who published a paper two years ago predicting a rupture in the San Andreas fault within 100 years. "The amount of energy released during the Chino Hills quake was less than 1% of energy from a potential great earthquake on the southern San Andreas fault."

The local media was scornful. "Whole lotta shakin', little damage," trumpeted the Los Angeles Daily News. "Ho, hum, another not-the-Big-One," declared the LA Times: "Swimming lessons, filming and pedicures are interrupted, but most people return to their routines fairly quickly."

Jones was keen to move away from the flippancy and focus on the quake as a "teachable moment". "A lot of people felt it pretty strongly," she said. Kate Hutton, her colleague at the California Institute of Technology, told a press conference in the hours after the tremor that it should be treated as a wake-up call, "an earthquake drill, a drill for the Big One that's coming some day".

Both Hutton and Jones are in the Big One business, and Chino Hills pushed that business to the front of southern California's collective consciousness.

Jones is the prime mover behind November's Great Southern California ShakeOut, described as the nation's biggest ever earthquake drill. If all goes to plan, millions of southern Californians will declaim the mantra of "Drop, cover and hold on" as they simulate their response to a 7.8-magnitude earthquake on the San Andreas fault, south-east of Los Angeles.

The earthquake model devised for the ShakeOut is, to put it mildly, alarming. Every 150 years, the southern San Andreas fault experiences an earthquake of the magnitude envisaged by the study. The last one was 151 years ago. As one seismologist noted last year, the fault "is 10 months pregnant".

"It's absolutely inevitable," said Jones. "The only question is whether it is in our lifetime." One recent study by the US Geological Survey put the likelihood of such an event happening in the next 30 years at 46%. The probability of a 6.7 magnitude quake was estimated at 99%.

According to Jones, the Big One in her model will cause 1,800 deaths and $213bn in economic losses. That's the good news. The bad news is far more scary. The initial tremor will cause buildings to collapse, freeways to buckle, pipes to burst, craters to open in the ground, and fires to start.

"The biggest surprise for me in the study was the fires following the earthquake," said Jones. "We estimate there will be 1,600 fires requiring the presence of at least one fire engine [each]. We don't have that many fire engines in southern California."

Fire, in a region already plagued by wildfires, would double the total losses of a major earthquake, she said.

Jones has more bad news. Burst water mains will leave many areas without a water supply for six months; sewer lines will break; there will be 50,000 injuries requiring a visit to casualty, assuming the hospitals have electricity and water and are still standing. And, she notes, all the big freeways going out of LA cross the San Andreas fault.

It's enough to make you pack your bag and head east. But southern Californians, if one believes the internet message boards buzzing after Tuesday's quake, are made of sterner stuff.

"California boy, born and raised," flatwrld posted to the San Diego Union Tribune website. "People call us fair-weathered, then tremble at the knees when the Earth farts." Another, identified as bluehair, hoped that "Maybe the quake will shake out all the guys from Boston that transplanted here."

Local repudiation of danger found an earlier expression in 1934, in the LA Times. "No place on Earth offers greater security to life and greater freedom from natural disasters than southern California," the paper pronounced, one year after a 6.7-magnitude earthquake in Long Beach left 115 people dead.

"I think internet conversations are just reproducing pulp images of southern California," said Mike Davis, academic and author of the LA-defining City of Quartz and the subsequent Ecology of Fear. "Most people are not here for the thrills or an urban version of Magic Mountain."

Davis argues that southern California, torn between a political reluctance to levy taxes to address the problem and a reticence on the part of big business to step in, has essentially closed its eyes to the potential destruction of a major earthquake.

"The politics of seismic safety is to forget," he said. After a shock such as the Chino Hills tremor or even the area's last major earthquake, in Northridge, a few miles north of downtown Los Angeles, in 1994, "there is concern, a few minor changes to the building code and then the politicians run away from the issue and the people go to sleep".

"Los Angeles requires a policy of seriousness," he continued. "We face seismic hazards. We should be under no illusion that 20,000 dead is not an impossibility."

Davis points to a 20-year-old report, by the now defunct California Division of Mines and Geology, which modelled a significant quake on a lesser fault, the Newport-Inglewood Fault, running from Beverly Hills to Costa Mesa, 37 miles south of Los Angeles. "It's one of the most frightening apocalyptic things I've ever read," he said. "It exceeds any Hollywood disaster movie."

Hollywood, of course, has left us with one of the most enduring images of an earthquake in LA with the 1974 movie Earthquake, starring Charlton Heston, with a lot of shaky buildings and the tagline: "When the big one finally hits LA." The reality is liable to be somewhat different.

"The waterbed bounced my butt on to the floor," a survivor of the Northridge earthquake wrote in an online forum last year marking the 13th anniversary of the 6.7 magnitude quake. "I couldn't get up because the ground had liquefied making the wood floor look like waves. It was 4am and I thought I was having a flashback until the noise became deafening and the stench of snapping power lines filled the air. Then the walls began to crack. I thought it was game over. Left the country some weeks later."

Jones trusts that next time the people will stay to help rebuild. "Our conclusion is that the earthquake we looked at isn't too bad," she said. "We can reduce a lot of the losses. The question is will we have done enough that our economic system can get back together? Or will we have a Katrina-type situation where the economy can't get back because all the people have left?"

Earthquakes

1857 Fort Tejon, 7.9 magnitude Largest recorded earthquake in California history, as the southern San Andreas fault rips along 225 miles 1906 San Francisco 7.8 (above) Three thousand deaths and $524m in property damage, mostly caused by raging fires

1933 Long Beach, 6.4 115 killed in Los Angeles county, with $40m property damage

1989 San Fernando Valley, 6.1 65 deaths, more than 2,000 injured and $505m in losses

1994 Northridge, 6.7 20 miles north of Los Angeles. 57 deaths, 9,000 injured and $40bn in property damage

Southern California shakeout, 7.8 Biggest ever earthquake drill to simulate a quake south-east of LA, which would cause an estimated 1,800 deaths and $213bn in property damage Despite recent rumbles, experts say state not ready for 'inevitable calamity'