State Must Heed Lessons of Kobe, Experts Warn : Quake: Long Beach, Venice and Bay Area are vulnerable to similar severe damage from soil liquefaction, seismic specialists say. Retrofitting buildings and bridges is strongly recommended.
Ground failure in landfills that severely damaged and closed expressways, bridges and a monorail in the Kobe earthquake could easily cause similar problems in Long Beach, Venice and the San Francisco Bay Area, a leading California earthquake specialist has warned.
Peter Yanev, director of the engineering firm EQE International, said not enough is known about how to deal with liquefaction--in which water-saturated soils turn to jelly under strong shaking--to be sure that major structures are not fatally undermined.
But he said that observations by an 11-member EQE team studying what happened in Kobe confirmed that Japanese engineers’ attempt to anchor structures by driving piles deep into the earth, below the zones subject to liquefaction, was not a sufficient answer.
EQE is one of the most important U.S. firms in advising businesses how to protect their property against earthquake damage. Its officers also frequently advise government agencies. The Kobe earthquake is the 34th that the firm has sent teams to study.
Yanev and an EQE colleague, structural engineer Charles Scawthorn, discussed Kobe’s lessons for California on Monday in Osaka, a city about 20 miles from Kobe that is being used as a base by many earthquake experts.
Scawthorn said the lessons include:
* The need to retrofit 24,000 buildings constructed before a 1976 building code upgrade in California. This could cost several billion dollars, he said.
* The strong advisability of gas and water companies developing “smart” computerized sensors for identifying the location of leaks when earthquakes occur and rerouting water and gas past trouble spots. California trails Japanese and European countries in this, he said, noting that failures to stop gas flows at disruptive points can increase the danger of fire.
* The need to speed retrofitting of the state’s bridges, particularly the toll bridges across the San Francisco Bay. “Nothing has been done to strengthen the Bay Bridge in the more than five years since the Loma Prieta earthquake,” he noted.
Yanev said the Kobe damage that most impressed him--the collapse of a brand new bay-side expressway, a bridge slipping off its supports and the collapse of a monorail system on an offshore island--resulted from liquefaction.
Regardless of the deep piles driven to protect these structures, displacement caused by the shaking in the soft soils was so extensive as to largely destroy their structural integrity, he said. “On the 800-foot-long bridge, the columns did OK, but the bearings failed,” he said. “The deck moved and girders ended up half off their legs.”
On Rokko Island, he added, high-rise buildings stayed intact, but the entire island settled more than three feet, breaking the buildings’ utility connections.
“The biggest lessons of the earthquake, as far as I am concerned, is that we have too many assumptions about soft soils, and this is directly pertinent to many California locales,” Yanev said. “Displacements can be much greater than we thought.”
He believes there are many questions about whether bridges in Long Beach and the Bay Area are adequately anchored.
Focusing on fire danger, Scawthorn said gas leaks, electricity breaks and reactions from spilled chemicals are about equally responsible for fires after earthquakes. If gas leaks can be reduced and systems can continue to deliver water after a quake, fire danger can be significantly reduced.
He said 109 fires were caused by the 1971 Sylmar earthquake, 110 by the Northridge earthquake and about 250 by the Kobe earthquake. The ones in Kobe were by far the most destructive.
Los Angeles fire authorities had good emergency experience from fighting brush fires, did not have to deal with congested narrow streets and had back-yard swimming pools to use for water reserves, Scawthorn said. None of those advantages existed in Kobe.
Still, he said, San Francisco leads Los Angeles in the development of a computerized system to protect the integrity of its firefighting water lines, which are separate from its water lines for other purposes. The city had a $46-million bond issue to perform the work.
Another means of creating a more “robust” water system is to use iron pipes that can bend to some extent without breaking.
Scawthorn said that the EQE team had not found anything completely unexpected in the Kobe quake, and that the damage to structures built before a 1981 Japanese code upgrade was not surprising.
“I think the quake confirms a lot of things known already and reinforces conclusions that we’ve got to get our act together in California,” he said.
“It’s such a cliche to say we’ve got to get our act together, but if we don’t we’re going to see far greater disasters in the next two decades in the San Francisco Bay Area (and) Tokyo, and it’s unclear if L.A. has a worse or better chance,” he said.
* RELATED STORIES: A6-A7