On Solid Ground

By Peggy Waldman

The earthquake that nearly leveled San Francisco in 1906 was one of the worst natural disasters ever to hit the United States. Hundreds of people died and thousands of buildings suffered major damage in the temblor and ensuing fires.

Yet the “great quake” a century ago—which probably measured a jaw-dropping 8 on the Richter scale—also became a fountainhead of scientific knowledge, forming the basis of modern earthquake theory and paving the way to stronger, more quake-resistant structures.

To Bechtel Chief Seismologist Joe Litehiser, there is no mystery as to why some structures collapse during a major temblor, while others sustain little or no damage. “Professional execution of competent engineering is the key,” says Litehiser, who has been applying earthquake science to engineering and regulatory issues for 30 years. Today, he heads a team of five seismologists who help ensure that Bechtel projects are as quake-proof as possible.

Globally, a powerful quake with a magnitude of 8 or more occurs an average of once annually, and a major quake measuring 7 or more strikes an average of 17 times each year. Many of the biggest quakes occur offshore and far away from any towns. However, in populated areas such as northern Pakistan, where houses are constructed of brick and stone, events like the 7.6-magnitude Kashmir quake of October 8, 2005, are devastating.

Applying statistical probabilities, seismologists consider where earthquakes are likely to occur and predict their size and impact. For example, the U.S. Geological Survey predicts that within the next 30 years, there is a 67-percent chance that an earthquake with a magnitude of more than 6.7 will hit the San Francisco Bay Area.

“To design properly, engineers need to know what ground motions a structure must withstand,” says Litehiser, who has helped develop seismic design criteria for some 700 Bechtel projects. “As seismologists, we try to come up with that number.” Memories of earthquakes fade fast, he says, “so the seismologist’s job is to bang the drum and get people to take the risk seriously.”

It takes time, money, and commitment to engineering excellence to add earthquake protection to the list of things that a successful project must consider, but when disaster strikes, the planning pays off. Consider Bechtel’s construction of a liquefied natural gas plant on the northeast coast of Sumatra, Indonesia, in the 1970s. Located on a sand spit jutting into the Strait of Malacca, the site faced high risks of earthquakes and tsunamis. At the suggestion of Bechtel seismologists and hydrologists, engineers raised the foundation three meters before building the facility.

In December 2004, the Sumatra-Andaman earthquake generated a tremendous tsunami that wreaked havoc throughout Southeast Asia and caused damage to other facilities nearby. Yet the Bechtel-built LNG plant was running at full steam only hours after the quake.

In the late 1990s, Bechtel faced a skeptical client at a $2.5 billion petrochemical complex in Gujarat, India. Bechtel wanted to design the facility to withstand a potential earthquake such as one that struck nearby in the 1880s. “The customer’s managers thought we were spending money unnecessarily,” says Litehiser.

After review by two Indian institutes, Bechtel’s design was approved—which turned out to be a good thing. On January 26, 2001, a 7.7-magnitude earthquake similar to the earlier one destroyed an estimated 339,000 buildings in Gujarat—but the petrochemical project remained intact. “Our customer’s refinery suffered no structural damage, and it resumed operations shortly after the disaster,” says Litehiser.

Seismically sensitive design can be crucial to getting a project built. For example, in August 1999, Bechtel was negotiating to build a 777-megawatt natural gas-fired power plant in Adapazari, Turkey. Then an earthquake hit the area, throwing the project’s viability into question. “Bankers asked if our design allowed for such an earthquake,” says Litehiser. “Fortunately, our early studies accommodated that possibility. The project was able to move ahead without delay.”

What keeps Bechtel at the forefront of seismic design are engineers who respond to the seismologists’ drumbeats with both state-of-the-art conventional seismic design and world-class innovations in seismic safety. In the field of nuclear power, for example, Bechtel is promoting the use of seismic isolation—a system not yet widely accepted in the United States. By designing buildings on cylindrical bearings called isolators, engineers decouple structures from harmful ground motion. During a quake, buildings on isolators sway as rigid blocks, eliminating forces and drift that damage conventional structures. Isolators can reduce the effect of a quake measuring 8 on the Richter scale to a comparatively tame 5.

Bechtel also uses X-shaped steel plates known as ADAS (added dampening and stiffness) devices to dissipate earthquake effects. Designed and patented by Bechtel engineers, ADAS bracing grew out of the company’s nuclear industry experience.

“For the nuclear industry, we are one of the very few companies that can analyze seismic risks of large structures properly,” says Bechtel Fellow Orhan Gurbuz.

Bechtel has even been called upon to help government agencies improve seismic safety of large-scale infrastructure. For the past six years, the company has served as general engineering consultant for a seismic retrofit program undertaken by Bay Area Rapid Transit, the rail system in the San Francisco Bay Area. Bechtel also conducted a cost review for the seismic retrofit of the San Francisco-Oakland Bay Bridge, which is now under way with construction of a new eastern span.

Today, Bechtel engineers are at the forefront of work to develop better strategies to withstand severe shaking. “Our understanding of ground motion and what causes structural failures during earthquakes is continually improving,” says Litehiser.

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