The Benefits of Being Prepared
By Janice Castro
The enormous energy and resources that Californians have invested in getting ready for the Big One were amply rewarded last week. Since 1971, construction codes have been tightened, buildings have been reinforced, emergency backup water supplies and communications systems have been secured. In communities throughout the state, fire and police departments regularly practice earthquake evacuation and rescue responses, and neighborhood groups have organized self-help efforts.
Those precautions saved hundreds of lives. In San Francisco modern office high-rises, many standing on huge steel-and-rubber springs deep below their foundations, rode out the bucking movement, bouncing and swaying as much as 30 ft. from side to side without cracking open. Within minutes after the quaking subsided, emergency response teams, honed by hundreds of hours of drills, began rescuing victims, sealing off dangerously weakened structures and coordinating relief efforts.
Perhaps the most important planning efforts concerned ways of coping in the immediate aftermath of a disaster. The Pacific Gas & Electric Co. quickly shut off power in San Francisco to minimize chances that a spark might ignite gas leaking from ruptured lines. As a result, only seven buildings were lost to fire. Frightened residents in dozens of towns could find detailed instructions on household safety measures in their telephone books.
But as state and local officials were collecting congratulations on their efforts last week, troubling questions were being raised about two catastrophes: the collapse of a stretch of Interstate 880 in Oakland and the fall of a 50-ft. span on the Bay Bridge, which connects Oakland and San Francisco. In concentrating on the destructive potential of buildings, had government disaster planners overlooked the fragile condition of heavily traveled highways and bridges?
I-880, also known as the Nimitz Freeway, collapsed when dozens of its concrete vertical support columns shattered during the violent shaking of the earthquake. Steel support rods inside the columns snapped like raw spaghetti under the multimillion-pound weight of the four-lane upper roadway. Some construction experts last week expressed outrage that the steel rods inside the columns had not been reinforced to help them withstand a powerful quake. Said Peter Lehrer, co-chairman of the Lehrer McGovern Bovis construction firm, which managed the restoration of the Statue of Liberty and Ellis Island: "There is no excuse for what happened on the Nimitz. We have had the technology to guard against this sort of collapse for years."
There were reports that state officials had long known the freeway, completed in 1957, was dangerously weak but had moved slowly to mount a major renovation of the structure. Calling for a state investigation last week, Governor George Deukmejian said he had just learned that a 1982 state study concluded that I-880 needed major reinforcement to prevent its collapse in a strong quake. Engineering experts now say that simply wrapping the concrete columns in steel sheathing -- a common method used to shore up older bridges and highways -- might have substantially reduced the damage. Even more disturbing are the suspicions of some engineers that initial reinforcement work done on the freeway during the 1970s may have contributed to its collapse. In an attempt to strengthen the roadbed, steel cables were used to connect the road's slabs. But as sections of the highway began to collapse, these cables may have produced a domino effect, pulling down one section after another.
In addition to structural flaws in the highway, the condition of the ground it stood on may have contributed to the collapse. Like the buildings that toppled in San Francisco's Marina district, parts of the freeway are built on landfill in an area that was once under San Francisco Bay (30% of the land under the bay has been reclaimed by landfill since the turn of the century).
Under the enormous forces exerted by earthquakes, such landfill typically liquefies below its surface, turning into slush as the water is squeezed out. Because this quivering mixture amplifies the shaking motion of an earthquake, structures built on landfill are subjected to far more complex and powerful twisting and shaking than those that stand on bedrock. Stark evidence of the difference could be seen last week, as houses on bedrock stood intact across the street from ruins.
Design flaws also seem to have contributed to the fall of part of the Bay Bridge, which consists of two differently engineered sections. Between San Francisco and Yerba Buena Island, the Bay Bridge is, like the Golden Gate, a suspension span built to withstand winds of 100 m.p.h. by swinging from side to side. Between the island and Oakland is the section that failed. It is of a far less flexible, cantilevered design in which the roadway rests on vertical steel support towers. During the tremor, one such tower swayed, snapping off the 2-in. bolts that attached it to the upper roadway and allowing a 50-ft. section to crash down on the lower level.
Several other double-deck highways in San Francisco also sustained heavy damage in last week's quake. On Thursday, after large fissures were spotted in half a dozen support structures, officials closed the Embarcadero Freeway, which swoops high above the city's financial district. Cracks were also found in the Southern and Central freeways, which bisect other downtown districts. Although some experts insist that safe double-deck roads can be built, angry demands that all such highways in California's quake zone be dismantled are already being heard. In Los Angeles last week, County Supervisor Kenneth Hahn called for a halt in construction of a second deck over 2.6 miles of the Harbor Freeway.
Even thousands of miles away from the epicenter, Americans were warily eyeing their highways and buildings and calling for better planning. Along the New Madrid fault, which runs 150 miles southeast of St. Louis, seismic experts say that within the next ten years there is a 33% chance of a quake as powerful as the one that hit San Francisco. Many East Coast residents who think of earthquakes as a California problem were reminded last week that New York City, which in 1985 sustained a 4.0-point quake with no significant damage, may be struck by a quake even more powerful than the San Francisco temblor within the next 20 years. Such a quake would wreak havoc on New York City, with its shockingly decrepit bridges and highways, some of which are only now getting the attention they urgently need.
Final explanations of why some California structures collapsed and others did not cannot be arrived at overnight. Just as researchers must analyze air disasters for as long as a year to determine the precise cause, scientists at earthquake research centers from Berkeley to Buffalo will use data from the wreckage to simulate last week's quake. By using sophisticated computers to study the wrenching forces, they hope to learn how to limit the damage.
Ultimately, these studies will yield valuable lessons in how to save lives and protect property. For example, one new technology based on studies of earlier quakes protects high-rise towers and bridges with shock absorbers made of rubber and lead. As small as toaster ovens, these seismic shock absorbers can reduce the force of a mighty 8.0 quake to a mere 5.0, hardly powerful enough to crack a sidewalk. As Californians marveled about how much more horrific last week's quake might have been without their preparations, they were also looking at a laboratory for prevention. Excruciating as the lessons are, tough-minded planning can reduce the tragic price the next time the earth heaves and buckles underfoot.
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CREDIT: TIME Charts by Cynthia Davis
[TMFONT 1 d #666666 d {Source: Michael O'Rourke, Renselaer Polytechnic Institute}]CAPTION: BENDING WITHOUT BREAKING
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[TMFONT 1 d #666666 d {Source: Michael O'Rourke, Renselaer Polytechnic Institute}]CAPTION: DESIGNED TO SURVIVE
The way structures are designed can make or break them when an earthquake strikes. Some lessons are learned the hard way:
HIGHWAYS: The worst structural failure was the double-decker I-880, where a number of concrete columns gave way. Built in the 1950s, the columns had vertical steel rods inside, but they lacked the spiral reinforcing rods used in modern construction.
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CREDIT: TIME Charts by Cynthia Davis
[TMFONT 1 d #666666 d {Source: Michael O'Rourke, Renselaer Polytechnic Institute}]CAPTION: DESIGNED TO SURVIVE
The way structures are designed can make or break them when an earthquake strikes. Some lessons are learned the hard way:
BRIDGES: Although built within one year of each other, the Bay Bridge, with its less flexible cantilever design, failed while the Golden Gate, having a more supple structure, swayed but did not give way.
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CREDIT: TIME Charts by Cynthia Davis
[TMFONT 1 d #666666 d {Source: Michael O'Rourke, Renselaer Polytechnic Institute}]CAPTION: DESIGNED TO SURVIVE
The way structures are designed can make or break them when an earthquake strikes. Some lessons are learned the hard way:
GAS AND WATER LINES: Costly earthquake proofing has yet to be accomplished on San Francisco's buried piping systems. It would involve installing joints between the pipes that could stretch and compress during a quake, preventing gas leaks and water damage.
With reporting by Robert W. Hollis/Oakland, Jeanne McDowell/Los Angeles and Sophfronia Scott/New York