National Geographic : 1995 Apr
Deck of cards adds a touch of whimsy to the $155 Execpak-an unsettling reminder that scarcity could fol low a major quake. Safety officers at cor porations and govern ment offices buy their employees this survival kit or smaller ones, which fit neatly into desk drawers. II NationalGeographic, April 1995 One of the greatest hazards in San Francisco is its hundreds of older, unreinforced brick buildings. Chinatown, for example, is filled with these structures, which easily collapse. Unlike Los Angeles, which more than ten years ago began requiring that brick structures be strengthened, San Francisco and most other California communities have been slow to act. Poor people live in many of those buildings. Stricter rules would threaten their housing. Officials are acting more urgently to retrofit the world-famous Gold en Gate and San Francisco ... _.. -Oakland Bay Bridges. Engineers warn that both must be exten sively upgraded to safely with . stand the big quakes expected. In the 1989 quake a small section of the Bay Bridge's upper deck / collapsed onto the lower road way, closing that vital artery for ? a month. SMuch more destruction could occur in the more powerful shak ing experts anticipate. The piers, which rest on timber pilings, could be damaged. Engineers say that while neither the Bay Bridge nor the Golden Gate is likely to collapse in their over-water sections, their approach ramps are vulnerable. Some trusses / that support the roadways could also buckle. "About 250,000 cars a day use the Bay Bridge. At any one time 4,000 people are on it," says . Abolhassan Astaneh, a civil engi neering professor at the Universi ty of California at Berkeley who led a recent detailed analysis of that structure. Beyond the obvious life-safety questions, Astaneh says closing the bridge for a year or more would be economically devastating. "The state's policy now is that major bridges should be completely func tional after an earthquake," says Astaneh, noting that the Bay Bridge is "the most complex structure I have ever seen. Strengthening it is going to be a very big challenge." Work on both bridges is scheduled to begin this year and take several years to complete. The cost will run more than 100 million dollars for the Golden Gate and 350 million dollars for the Bay Bridge. Seismic hazards persist north of San Francisco, especially in the wine country of Sonoma County. The city of Santa Rosa was leveled by the 1906 quake, but today the Rodgers Creek Fault worries David Schwartz more. "We think we see three big earthquakes in the past thousand years," says Schwartz at a trench his team has dug across the fault. "They occur on aver age every 230 years. We think the last one was about 1650. This fault can create at least a 7. There'll be a lot of wine on the ground."