Simulation by Robert Graves. Rendering by Geoff Ely, UCSD/San Diego Supercomputer Center.

Ground motions in the ShakeOut scenario 60 seconds after the rupture begins. Yellow regions are experiencing sideways motions of one meter per second or more.

Brace Yourself!

It’s a good thing that Lucy Jones didn’t want to scare us, as she kept assuring the capacity crowd for the press conference in Caltech’s Beckman Auditorium on June 4—if she did, the audience would probably have been reduced to blubbering imbecility. Jones, a Caltech visiting associate in geophysics and the chief scientist of the United States Geological Survey’s Multi-Hazards Project, was describing the scenario created for what will be the largest earthquake drill ever held in the United States.

“ShakeOut,” as it’s called, will cut loose at 10:00 a.m. sharp on Thursday, November 13, and features a magnitude-7.8 quake on the San Andreas fault that begins under the shores of the Salton Sea at Bombay Beach, and in 90 terrifying seconds ruptures 180 miles of fault to well west of Lancaster. The ground will move sideways 44 feet in places, and the sedimentary layers of the L.A. basin will quiver like angry Jell-O for 55 seconds—an eternity compared to the magnitude-6.7 Northridge quake’s seven seconds. It will take up to three minutes for all of the shaking to die out in some places.

The freeways that cross the fault will be reduced to rubble, and our other lifelines—railways, power lines, and aqueducts—will fare no better. “We’ll have 13 million victims,” Jones said, “and we’ll need help from the Bay Area and Arizona at a time when I-10 and I-15 have been cut.”

“This is nearly as big as the event that just hit China,” said the USGS’s Ken Hudnut, a Caltech visiting associate in geophysics, who, like many others involved in ShakeOut, wears a red silicone wristband for the Chinese earthquake victims. Hudnut and Brad Aagaard (MS ’95, PhD ’00) created a highly detailed specification of the earthquake source. Hudnut then oversaw the quake’s computer modeling, in which the San Andreas fault was divided up into some 18,000 “sub-faults,” each about 500 meters square, along which the slip was forced to propagate, mimicking the rupture of the real thing. (Hudnut also plans to model some of the scenario’s larger aftershocks, one of which is a 7.2 on the Sierra Madre fault, aimed right at Pasadena.) Robert Graves (MS ’88, PhD ’91) of URS Corporation turned this data set into a detailed simulation on the University of Southern California’s high-performance computer cluster, calculating the shaking experienced across the Southland at points spaced on a two-kilometer grid. The ShakeOut simulation project was coordinated by the Southern California Earthquake Center (SCEC), and several other SCEC institutions participated.

The ShakeOut scenario, all 308 pages, was constructed by over 300 experts from the USGS, Caltech, SCEC, UCLA, and elsewhere who used Graves’s results to create a plausible picture of likely damage to buildings, roads, pipelines, and the like, which in turn were used to project casualties and economic losses. For example, Swaminathan Krishnan (PhD ’03), assistant professor of civil engineering and geophysics, and postdoc Matthew Muto modeled the respose of multiple 20-story steel-frame buildings at each grid point, paying special attention to the dozen or so locations that have cluseters of tall buildings.

“It’s not the worst case, but it’s a real good estimate of what we can expect,” said Federal Emergency management Agency geophysicist Michael Mahoney. Since our building codes are stricter than China’s, only five 11- to 20-story steel-frame buildings collapse completely, and just one percent (45,000) of the region’s lesser structures are total losses, with one in 25 wood-framed houses and apartment buildings suffering significant damage. With no Santa Ana winds to fan the 1,600 blazes that are started by car crashes, downed power lines, and the like, a mere 133,000 single-family houses are destroyed. “Find an open space of refuge—a park, or a school, perhaps—in your neighborhood,” said Michael Freeman, chief of the Los Angeles County Fire Department. “Where would you go if several city blocks are burning?”

The point to all this, of course, is for local, state, and federal agencies to plan their responses. “How do you deal with an event that will literally break the system?” said SCEC director Thomas Jordan (BS ’69, MS ’70, PhD ’73). Thousands of cops, firefighters, and paramedics will be deployed in the statewide “Golden Guardian” exercise, and logistics will be a big focus. “You’ll have to think about how you’ll feed your first responders three days later,” as Jones pointed out—no easy task, even though the ports and the airfields are largely intact, when all the roads are impassable. Getting electricity, water, and other basic services restored will take days to weeks, and some of the hardest-hit areas will be doing without for months. And then there’ll be the 1,800 dead and 50,000 injured to deal with. . . .

But this isn’t just for the pros—millions of ordinary Californians, in their schools, businesses, places of worship, or just at home, will take part in the drill, not only by “Dropping, Covering, and Holding On, as the slogan goes, but by creating or updating their own disaster plans. (See http://www.shakeout.org/.) There’s no time like the present to get prepared—as Jones says, “A large earthquake is definitely in our future.”—DS