What a 7.8-Magnitude Quake Would Do to California

The 7.8-magnitude earthquake devastated China this month, killing 51,000 (29,000 are still missing). A quake of that size would also devastate Southern California, according to the most rigorous simulation of its kind, done in preparation for a statewide earthquake drill, Golden Guardian 08, in November.

The ShakeOut Scenario projects 1,800 deaths, 50,000 injuries and $200 billion in damage, in addition to "long-lasting social and economic consequences" from a major quake on the San Andreas Fault

Published by the U.S. Geological Survey and the California Geological Survey, ShakeOut is being presented at a House Energy and Mineral Resources subcommittee meeting.

Southern California Earthquake Center

Here's a look at the projections, in the words of USGS:

• The strongest shaking and greatest damage is near the stretch of the San Andreas Fault that extends through the fastest growing areas of Southern California, including the Coachella Valley, Inland Empire and Antelope Valley.

• At least 10 million people will be exposed to heavy shaking. California's efforts at mitigation have concentrated on life safety and have been largely successful. Thus, in spite of the large numbers of people in highly shaken areas, deaths are estimated at only 1,800.

• Building types known to be vulnerable to damage and collapse, do indeed sustain major damage. All un-reinforced masonry buildings within 15 miles of the San Andreas Fault are completely destroyed. Those that are not retrofitted kill many occupants. Many other older building types without retrofitting contribute to over $33 billion in damage to buildings.

• The fault offsets all lifelines crossing into Southern California at Cajon Pass (Interstate 15), San Gorgonio Pass (Interstate 10) and along Route 14, including pipelines, power lines, roads, railways, telecommunications and aqueducts.

• Strong shaking continues in downtown Los Angeles for 55 seconds, nearly 8 times longer than in the Northridge Earthquake

• The prolonged, strong shaking heavily damages and sometimes collapses hundreds of old brick buildings, thousands of older commercial and industrial concrete buildings, many wood-frame buildings, and even a few, high-rise steel buildings. Over 600,000 buildings suffer at least some damage that causes tens of thousands of injuries and hundreds of deaths, and leaves many thousands of people without homes or jobs.

• Fire doubles the fatalities and economic losses. Around Southern California, there will be 1,600 fires started large enough to warrant a 911 call, and some fires merge into conflagrations that burn hundreds of city blocks. Assuming no Santa Ana winds, the models still indicate a further $65 billion in direct losses and $22 billion in indirect losses from the fires.

• Nearly two thirds of the hospital beds are non-functional in Los Angeles, Orange, Riverside, and San Bernardino counties. At the same time, 50,000 people will seek treatment at emergency

• Thanks to a $6 billion investment in seismic safety, the State highway system fares well. However, although collapse is avoided, some bridges are non-functional so that much of the highway is not passable on the day of the event. The long duration of shaking takes a greater toll on bridges and overpasses under the jurisdiction of cities and counties where the retrofitting processes are not complete or have not begun.

• The largest long-term economic disruption comes from damage to the water distribution system. Damage to this system will be so extensive that some areas will have to replace the whole system, and some buildings will be without water for as long as 6 months. The direct and indirect business interruption costs attributed to the lack of water will be $50 billion.

The USGS urges people to prepare now by storing water, being prepared to use a fire extinguisher, securing furniture and possessions that might otherwise topple in an earthquake and reinforcing buildings to meet government standards.

Here's how the USGS described the Shakeout research:

The ShakeOut Scenario is the product of an interdisciplinary collaboration of over 300 scientists, engineers, and other experts from several agencies, including the USGS, the California Geological Survey, Southern California Earthquake Center, California Office of Emergency Services and Seismic Safety Commission.

To create the Scenario, geologists determined the amount of potential motion on the part of the San Andreas Fault with the greatest risk of imminent rupture, a 200-mile long section from the Salton Sea in the Coachella Valley to just south of Gorman. From this, seismologists and computer scientists modeled the ground shaking. Engineers and building professionals used the models of ground shaking to estimate damage to the built environment. And from these damages, social scientists evaluated emergency response, casualties, and the impact on our economy and society.

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