(Recasts, adds color, quotes from triage drill) By Steve Gorman and Syantani Chatterjee LOS ANGELES, Nov 13 (Reuters) - Millions of Southern Californians, many with a sense of amusement, simultaneously crouched under tables and desks for two minutes of imagined seismic turmoil on Thursday in the biggest U.S. earthquake drill ever. The Great Southern California ShakeOut was organized by scientists and emergency officials to help prepare the region's 22 million inhabitants for a catastrophic quake that experts say is inevitable and long overdue. The drill was based on the premise of a magnitude 7.8 quake striking the southern portion of the famed San Andreas Fault, a subterranean chasm between two massive plates of the Earth's crust that extends hundreds of miles (km) across the state. The hypothetical temblor, similar in strength to the devastating tremor that hit China in May, also is the basis for this year's Golden Guardian exercise -- a days-long annual disaster rehearsal for emergency-response agencies statewide. "Every day in the back of our minds, all of us, everyone of us in Southern California, knows that the 'big one' is coming," Los Angeles Mayor Antonio Villaraigosa said at news conference. "The question is not if it happens but when, not whether it strikes, but with what magnitude." Villaraigosa spoke at a simulation where firefighters practiced medical triage on hundreds of students from Bishop Alemany High School. Many wore casualty makeup to play the role of quake survivors pulled from a collapsed building. The most severely injured "patients" were whisked off in wheelchairs and gurneys to an adjoining hospital. UPBEAT MOOD PREVAILS Despite the gravity of the event, students made up with head wounds and broken bones chatted and joked about their appearance as they waited to receive first-aid. The mood was similarly upbeat miles away at the 21-story Nestle USA headquarters in Glendale, where 1,600 employees in business attire dutifully crawled beneath their desks when the drill began, as giggles and banter abounded. Sales associate Jared Bogda, 25, admitted afterward he felt "a little silly" but insisted the exercise was worthwhile. "Being from the East Coast, it was a change for me," he said. "At first I thought 'Oh, this is really ridiculous' ... . But you know what? You've got to do what you've got to do." More than 5.3 million people -- about a quarter of Southern California's population -- signed up for the drill, including entire school districts and college campuses. Many more were thought to have joined in without registering. Organizers said they were aware of only one such exercise on a bigger scale -- a drill for 8 million school children in South Korea about six months ago. Japan holds large-scale quake drills every year. 1,800 ENVISIONED DEAD Thursday's event began at precisely 10 a.m. PST (1800 GMT), with people in classrooms, offices and homes asked to perform the "drop, cover and hold-on" exercise for two minutes. Some were guided by a pre-recorded public service message, accompanied by sounds of a rumbling quake, distributed in advance and aired by radio and TV stations. The quake scenario devised by geophysicists and engineers envisioned a calamity that would leave 1,800 people dead, 50,000 injured and 250,000 homeless. Property losses of at least $200 billion are projected. A rupture of the San Andreas Fault in Northern California caused the estimated 8.3-magnitude quake that laid waste to San Francisco in 1906. The last "big one" to strike south of the San Gabriel Mountains, near Los Angeles, was 300 years ago. The average interval between such quakes in that region is 150 years. The biggest Southern California temblor in recent years, the 6.7-magnitude Northridge quake in 1994, killed 57 people and caused about $40 billion in damage. (Editing by Dan Whitcomb and Xavier Briand)
Los Angeles mayor Antonio Villaraigosa (C) speaks to a simulated victim inside a mobile field hospital during the Great Southern California Shakeout, an earthquake drill simulating a 7.8 magnitude quake at ...
