Kobe Quake Raises Doubts About Safety of California Highways and Buildings

Etsuzo Shima, one of Japan’s most respected seismologists, shook his head as he looked at photos of a collapsed freeway. The road in the photos was not in Kobe, devastated by a 6.8 earthquake last month. It was in San Francisco and the year was 1989.

I had sought him out in Tokyo shortly after the Loma Prieta earthquake to ask what he and his colleagues had learned from that California temblor. It had broken the rules by destroying structures thought to be able to withstand such a quake centered more than 50 miles away. After the Kobe quake, with its haunting scenes of toppled freeways, I dug out my notes to see what Shima had said then about the elevated freeways that run through nearly every major city in Japan.

“The engineers say (the freeway system) is all right,” he had said, “but when we go over that type of highway it moves.” He had paused for a long moment, then added softly: “I’m not so sure.”

Unspoken but clearly implied in his answers was a deeply rooted fear: Perhaps we have placed too much faith in earthquake engineering.

Shortly after returning home I sat down with a distinguished California engineer who had helped draw up the guidelines for making buildings that could stand up to earthquakes. He, too, was not so sure, and during our off-the-record interview he said bluntly that he feared nature would someday mock his earlier confidence.

“We have made the assumption that a great earthquake is just like a smaller earthquake, only bigger,” he said. “But I’m no longer sure we can just scale up our specifications to absorb the higher energy levels of a stronger quake. It may be that an earthquake of magnitude 8 or greater performs quite differently.”

Scientists have a term for that, non-linear. It means that a great quake may cause far more damage than its measured size would suggest.

The problem is that we really don’t know how a modern city with state-of-the-art buildings will perform in a truly catastrophic earthquake, because no modern city has been hit with one. A magnitude 8 quake would unleash more than 30 times the energy of the Kobe quake, so our engineering for great quakes remains largely untested.

Some day, we will find out.

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There are several candidates for that dubious distinction, but Los Angeles probably is not one of them. The power of an earthquake depends on the length of the fault, and the damage it causes depends largely on its center’s distance from vulnerable structures. The only known Southern California fault capable of such a quake is the notorious San Andreas, and it is more than 40 miles from Downtown.

The San Andreas rips through the heart of San Francisco, but since it ruptured there as recently as 1906, most experts think San Francisco--like Los Angeles--should be more worried about large quakes on nearby faults than a great quake occurring along the San Andreas.

Seattle could be the best candidate on the West Coast: research over the past few years has turned up evidence of massive faults along the Oregon-Washington coastline that could produce such a quake. Those faults are not clearly defined, however, and any great quake could be centered some distance from downtown Seattle.

So my guess is the test will probably come in Japan--not in Kobe, but Tokyo.

“Tokyo is the most dangerous place in all of Japan,” one top engineer told me during interviews there. It sits atop a complex matrix of large faults, several of which could yield a magnitude 8 temblor.

Japan’s National Land Agency concluded from a 1988 study that if a great earthquake should strike Tokyo in the middle of the night, it would kill about 80,000 people. If it came at lunch time, as did the 1923 quake, or in the evening when stoves would be lit for cooking and heating, fires would sweep parts of the city and the death toll could reach 150,000.

When the great quake strikes Tokyo it will hit a city already so overcrowded that its traffic jams routinely surpass those Los Angeles has to offer. Rescue crews will be blocked by damaged highways. Water mains will be broken, so fire fighters will be unable to fight the inevitable fires.

“In the 1923 earthquake 100,000 people burned to death,” said Hirokazu Iemura of Kyoto University’s Earthquake Engineering Laboratory, referring to Tokyo’s most devastating quake to date.

Nario Oyagi, a geologist-engineer with Japan’s National Research Center for Disaster Prevention, told me he is awakened in the middle of the night by a recurring nightmare: He sees endless streams of cars ablaze on crowded streets, like ribbons of fire extending out into the suburbs.

“We have cars, so many cars, always crowded on the street,” he said. “If one or two cars catch on fire. . . .”

The scene of a great city burning from its core, isolated from outside help by unthinkable disaster, is particularly haunting in these days since Kobe.

As I combed recently through my stack of notes from my trip through Japan, I was struck by a troubling dichotomy.

The seismologists were deeply worried.

But the earthquake engineers, widely regarded as among the best in the world, were confident they were designing structures that would withstand any credible earthquake.

Kobe proved they were far too confident.

No one knows if their engineering is adequate for a truly major quake. The same could be said of California.

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Lee Dye, a former science writer for The Times, has covered a broad range of science subjects for more than two decades. He divides his time between Alaska and the Southwest, writing for several publications. E-mail him at [email protected] .