When the Loma Prieta earthquake ripped through the San Francisco Bay Area on Oct. 17, 1989, it cut a terrifying path of destruction that forever changed the way Californians think about living in quake country.
The 6.9 magnitude rupture of the San Andreas Fault toppled houses, crushed a freeway and collapsed a section of the San Francisco-Oakland Bay Bridge. Sixty-three died, more than 3,750 were injured and the damages were estimated at more than $6 billion. Not since the great 1906 San Francisco earthquake had California experienced such a devastating seismic event.
Yet if there could be an upside to those 15 seconds of deadly shaking, it would be in the scientific and engineering advances that grew out of Loma Prieta. Twenty years later, researchers are still learning from Loma Prieta, and UC experts continue to play an integral role in ensuring those lessons are translated into practical solutions that make California more quake resistant.
"Each earthquake tells us a story," said I.M. Idriss, a professor emeritus of geotechnical engineering at UC Davis. "Sometimes it's confirming something we know or sometimes it tells us something we didn't know."
Idriss, along with UC Berkeley professors Joseph Penzien and (the late) Alexander Scordelis and other government and academic researchers, served on the Governor's Board of Inquiry, appointed by George Deukmejian in the weeks following the temblor. The governor charged the board with finding out why the bridge and freeway structures failed and how the state could keep it from happening again.
Wake-up call
There had been modern earthquakes in California that damaged bridges and freeways before Loma Prieta. The 1971 San Fernando earthquake collapsed an Interstate 5 interchange that was under construction. The 1987 Whittier Narrows earthquake caused another freeway bridge on I-5 to fail. Those quakes exposed performance problems that resulted in California Department of Transportation retrofit programs. And the 1994 Northridge earthquake would reinforce the need for seismic vigilance. But it was the unprecedented destruction to the high-profile Bay Area structures that turned earthquake safety into an urgent public priority in California.
The Board of Inquiry made dozens of recommendations for retrofitting bridges and highway structures, improving design standards and promoting the safety of the state's transportation systems. Earthquake resistance became the highest priority in state construction projects.
Serving the state
Idriss has been involved with every major quake on the globe since the great Alaska earthquake of 1964. He is part of a group of engineers who descend on a region in the aftermath of a major quake to analyze damage and determine causes of structural collapse. Loma Prieta is the only quake he has experienced first hand.
After the Board of Inquiry issued its report in 1990, Idriss and several other UC researchers continued to work with Caltrans serving on the state's Seismic Advisory Board and on peer advisory panels for all the Bay Area toll bridge retrofit projects. That includes the Bay Bridge retrofit and the construction of the bridge's new eastern span. In these advisory roles, UC researchers review designs and suggest construction techniques and changes to building standards. It's hard to drive anywhere in California without crossing a structure UC hasn't had a hand in building or repairing.
California has become a model for other states in its seismic safety practices and policies, said Michael Keever, chief of the Caltrans Office of Earthquake Engineering, and he credits UC's involvement with propelling the state into that leadership role.
"UC research has been the cornerstone of the improvements we've made in both our retrofitting and new design policies," Keever said. "We've changed our practice on the work they've done."
Pioneering research
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| Frieder Seible, dean of the Jacobs School of Engineering at UC San
Diego,
is a peer adviser for toll bridge retrofits such as that for the Bay Bridge. |
The university has been at the forefront of seismic research since 1887, when the first seismographs in North America were installed at the UC-owned Lick Observatory on Mount Hamilton and at the UC Berkeley campus.
The Pacific Earthquake Engineering Research Center, one of the sponsors of the Loma Prieta Earthquake Commemorative Symposium on Oct. 17, is based at UC Berkeley and dedicated to promoting earthquake engineering technologies and to supporting decision-making about seismic risk.
Among UC quake research centers are five Network for Earthquake Engineering Simulations facilities. The National Science Foundation-sponsored centers are located at Berkeley, Davis, UCLA, San Diego and Santa Barbara. Researchers around the globe use the centers to fake earthquake shaking to test the effect on buildings, bridges, dams and other structures.
The big shaker
When engineers need to test something really big, like a seven-story building, they turn to UC San Diego's Englekirk Structural Engineering Center. Part of the national simulation network, it is home to the world's only outdoor shake table and the largest in the United States. The shake table simulates the ground motion of large earthquakes to test the way structures will react. The table can hold up to 2,000 tons and models 100 feet tall.
Frieder Seible, dean of the Jacobs School of Engineering at UC San Diego, is a world leader in bridge design and large-scale structural testing. He serves as chair of the Caltrans Seismic Advisory Board and is a peer adviser for the toll bridge retrofits. When workers cut away a section of the Bay Bridge over the 2009 Labor Day holiday to connect a temporary detour until the new span is completed, Seible was on the bridge observing.
"It's a little bit nerve-wracking sometimes," he said. "We're the ones telling Caltrans how it should be done. What if it doesn't work?"
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| Maria Feng, a civil engineering professor at UC Irvine, has been
testing a sensor system that can detect seismic effects on buildings and bridges. |
Making sure the design and construction methods do work is where the simulation centers come in. Components of the new eastern span of the Bay Bridge were tested at UC San Diego. Now the facility is testing the bearings for the Dumbarton and Antioch bridge retrofits in the Bay Area. The center also is testing how structures can withstand manmade events such as a terrorist attack.
"Clearly we are still learning with all the research going on," said Seible. "We constantly have to revisit what we did. There's never a state where we're done. Clearly the lion's share of the research is being done at the University of California."
That research not only makes our structures safer, it also can save money. At UC Davis, the Center for Geotechnical Modeling, part of the simulation network, last year built a model of Bay Area Rapid Transit's Transbay Tube to evaluate the need for retrofit work in the soil that surrounds the underwater tunnel. Consultants working on the transit district's seismic safety program wanted to verify their calculations on the vulnerability of the tube before an expensive retrofit project was taken on. There was concern that in a big earthquake, the soil this vital transit link between the East Bay and San Francisco rests on would liquefy and the tube would float loose, rupture and flood commuter trains with water, said Bruce Kutter, professor of civil and environmental engineering. The centrifuge testing simulated the amount of motion the Loma Prieta quake created near the tube and a stronger 1999 quake in Taiwan.
"Looking at it more they found that even if the ground liquefies, the tunnel isn't going to move very far. So we saved the retrofit cost," said Kutter, who was director of the modeling center from 1996 to July 2009.
The bridge doctor
At UC Irvine, Maria Feng, a civil engineering professor and founder of the Center for Advanced Monitoring and Damage Inspection, has been testing a sensor system that can detect the effect of earthquake and normal aging on buildings and bridges.
"We try to find out the health condition of the structure before there is extreme danger in a sudden failure," said Feng.
The fiber optic sensors she developed can be manufactured at a third of the cost of the electric sensors currently used, she said. Three Orange County highway bridges and the Vincent Thomas Bridge in San Pedro are test sites for the sensor system. State bridges are typically inspected visually every two years. Feng's system can detect damage remotely in real time.
"We hope to link this sensor data to the traffic control centers, so they could direct the emergency response more efficiently," said Feng.
Often structures are closed after an earthquake until inspectors visit and determine if damage has occurred. This would let Caltrans know which structures are damaged and which can stay open for traffic. The system can also help the state prioritize retrofit work by showing which bridges are experiencing cracks and which need immediate repair.
Keeping research dollars flowing to projects like this is a challenge. After a major quake, research funding gets a boost, but California hasn't had a major destructive quake since Northridge. Remembering Loma Prieta, researchers say, hopefully will remind all Californians — from consumers to funding agencies — to prepare for the next quake disaster that surely awaits us.
"The really big lesson we learned from Loma Prieta is that we should not and cannot become complacent," said UC San Diego's Seible. "We will get another big one, so we need to prepare and continue the research."
| Is California safer than it was 20 years ago when Loma Prieta struck? Here's what some UC quake experts say: |
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"I feel very bullish about the safety of our transportation structures. I feel we have done so much that the next big earthquake will show our bridges perform very well."
Frieder Seible, dean, Jacobs School |
"Technological advances have really been speeding up how fast we can communicate information about an earthquake to governments, utilities and railways, so they can do rapid responses like stopping trains and inspecting bridges. Our response capability in California is getting better every year, although it's still not quite as advanced as in Japan." Thorne Lay, professor of Earth and planetary sciences, UC Santa Cruz |
"We are safer. But we can't have zero risk. We could never afford it, and I'm not sure we can achieve it."
I.M. Idriss, professor emeritus of geotechnical engineering, |
"Nothing is invulnerable. There can always be a bigger earthquake. At the same time the technology has gotten better, the population increased and the infrastructure has gotten denser. There's still vulnerability. You have to keep up with the growth." Bruce Kutter, professor of civil and environmental engineering, UC Davis |
Donna Hemmila is managing editor at the UC Office of the President's Integrated Communications group.