Japanese Quake Stirs Global Look At Design Weaknesses
FOR engineers, Kobe's devastation is another ``stern warning'' to make the most of earthquake safety knowledge.
Most experts agree that buildings can now be designed to withstand major quakes - as many did in Japan. But refitting old buildings and creating topple-proof new ones can be enormously expensive - as the destruction of more than 21,000 structures in Japan shows.
Therein lies a crucial question now facing the country as it struggles to dig out from its worst quake in half a century: How much the balance between safety and economics should be shifted.
One lesson from the Kobe disaster seems clear: Designing buildings, bridges, and other structures to prevent the loss of life isn't enough. They have to be able to survive to the point where cities can still function. At the same time, other modern ``lifelines'' - water, communications, energy supplies - also need to be more earthquake proof.
In Kobe, far more people are suffering from loss of these ``lifelines'' than perished or were injured. The blow to Japan's economy is aggravated because Kobe has become a transportation choke point. The number of deaths from the 7.2-magnitude quake is now well over 4,000. More than 22,000 others have been injured. Early estimates indicate the cost of the damage could top $60 billion.
Haresh Shah, a civil-engineering professor at Stanford University, says societies need to take a ``comprehensive approach'' to earthquake mitigation that transcends the goal of merely designing structures to save lives but not property.
``This tragedy we have to take as a learning process,'' he says.
Dr. Shah, like other quake specialists, notes that one of the biggest unlearned lessons is the need for public officials and citizens generally to make full use of what the safety experts are learning.
That point was underscored in a National Research Council committee report on the Loma Prieta earthquake that hit San Francisco Oct. 17, 1989. In releasing the report last April, after a damaging quake hit the Northridge area of Los Angeles, committee chairman Lloyd S. Cluff remarked:
``The aftermaths of these earthquakes should make clear the need to close the gap between what scientists know about earthquake mitigation and what is used by governments and individuals.''
Safety experts stress they still have a great deal to learn. The failure of supposedly strong steel welds and four-inch thick steel plates in the Northridge quake Jan. 17, 1994, surprised everyone. Yet these recent quakes also show that current safety knowledge, where applied, does work.
A National Institute of Standards and Technology report on the Northridge quake noted that most structures designed and built after seismic codes were revised in the mid 1970s performed well. So did bridges that were retrofitted to meet the new standards. But older structures, such as unreinforced masonry buildings, took a lot of damage.
Although it is too soon to know what has happened in Japan, Kobe may show a similar pattern. Early surveys indicate that many of the houses destroyed seemed to be older ones made of wood frame with stucco walls. But some wooden structures did survive, while a few of the newer steel-framed buildings fell.
Part of the capriciousness of the quake is due to different soil conditions. Damage appeared to be greater near the coast, where the ground is softer and earth movements greater.
Shah points out that much of the devastation has been to old, often-flammable buildings. On the other hand, there are structural lessons to be learned as the collapse to supposedly strong highway platforms shows. Freeway sections made of heavier concrete collapsed while stronger - and costlier - segments supported by steel didn't.
Architectural engineer Lou F. Geschwindner Jr. at Pennsylvania State University, explains that quake mitigation ``is one of those things that's been continually developing.'' He adds that ``you don't have a complete understanding until you have an earthquake.'' He notes that the steel industry now is working to overcome the weakness in steel construction that appeared in the Northridge quake damage.
Computer-based simulations also bring new safety insights. Civil engineer John Hall at the California Institute of Technology in Pasadena simulates what the kind of shaking Northridge experienced does to buildings. He told a meeting last year that both modern 20-story buildings and older concrete structures could collapse. However, tall skyscrapers, which are strong enough to resist high winds, probably would also withstand the shaking.
Hall and several colleagues described further studies of this type in the Jan. 13 issue of the journal Science. One author, Thomas Heaton at the US Geological Survey office in Pasadena, says he is ``very confident'' that buildings can be built to withstand major quakes. He explains that reinforcing buildings with what are called shear walls that resist quake-induced stress can make a strong structure.
Studies such as these underscore the National Research Council conclusions that safety can be enhanced by reinforcing older structures as well as building strong new ones. Yet Stanford's Shah says that even this may not be enough. He notes that we know how to design safe buildings and bridges and in places like Japan or California much of this is being done. Yet disasters keep coming. ``I think it is because we aren't looking at it in an integrated way,'' he says.