DEVASTATING JOLT IN JAPAN : Some Lessons From Quake May Be Hard to Accept
Every sizable earthquake teaches lessons, some of them easier for society to accept and act upon than others.
When it is adjustments to procedures for an automatic shut-off of natural gas under heavy shaking, changes may be relatively easy.
When it becomes apparent that bridge columns or railroad overpasses or embankments ought to be constructed differently, and massive retrofits undertaken, it may be more difficult, but eventually it will be done.
But when scientists and engineers point out that much of the city of Kobe or the cities around San Francisco Bay are built on landfill--making urban development particularly vulnerable to earthquakes--it seems unlikely that such development will be halted or rolled back.
In California, such politically unpalatable information has impeded the state’s Seismic Safety Commission from advocating broad reforms in land-use planning.
But it is already evident here that visiting American earthquake experts tend to be far more outspoken than their Japanese colleagues in saying what needs to be corrected in Japan.
Peter Yanev, head of EQE International, a San Francisco-based firm specializing in earthquake engineering, bluntly stated Saturday that Japanese mistakes in the construction of bridges are “inexcusable.”
“The Japanese were so sure of themselves that they knew what they were doing that they made key mistakes,” Yanev said. “They were talking a good story and not doing things.”
Yanev and another visiting quake expert, UC San Diego’s Nigel Priestly, who was formerly a Caltrans bridge design consultant, said that the Japanese were building bridge columns much thicker than is the custom in the United States and that this reliance on brute strength was counterproductive.
By contrast, they said, Caltrans has emphasized ductility in design, or the capacity to bend without breaking. They noted that a Japanese government delegation that visited California after last year’s Northridge quake had criticized the American techniques and said the Japanese ones were better.
The thick columns gave way here in great numbers. Some Japanese engineers have conceded that, in building their bridges to withstand ground movement equivalent to 20% of the force of gravity, the Japanese had underestimated what stresses would occur.
Preliminary measurements of ground movement have indicated forces of 60% of gravity in downtown Kobe, Charles Scawthorne of EQE said.
Heavier movement than would be expected was also seen in the Northridge quake, and some engineers have expressed concern that American building standards must also be changed.
In light of the experiences in Kobe, policies on automatic gas shut-offs, a concept gas companies in California have been resisting, may also be reviewed.
Automatic gas shut-offs are much more common in Japan, and there have been estimates that 70% of Kobe’s homes were equipped with such a system.
But some fires may have been caused by gas line breaks. Despite a general shut-off of gas at the main station, there were reports that gas that had collected in the broken lines ignited.
Another problem with the Japanese system was that the shut-off was automatically triggered at homes only if the gas was on when the shaking began, said Barbara Zeidman, assistant general manager of the Los Angeles Housing Department who was in nearby Osaka for an earthquake conference when the temblor struck.
Because the earthquake took place at 5:46 a.m., and many Japanese families turn the heat off at night, the gas wasn’t shut off at several homes, Zeidman said.