COLUMN ONE : Lessons of Kobe: Hope, Caution : Design differences may give California’s housing, highways greater safety margins, experts say. But pace of retrofitting and risk of a major quake on a minor fault raise concern.

By ferry and train, the engineers come to Kobe.

Then, on foot, they pick their way through the rubble, carrying flash cameras and newly printed damage maps, trying to salvage the lessons that may enable cities like Los Angeles and San Francisco to better withstand the titanic forces unleashed by the agitated earth.

Already they have found enough to confirm growing disquiet about how older buildings, harbor facilities, landfill areas and utility pipelines may fare in a major urban earthquake. For example, a Kobe-like temblor on a relatively minor fault under the Port of Los Angeles might cause unexpected havoc among its older artificial islands, bridges and rail yards, some experts now worry.

Many experts, however, are also finding evidence for renewed confidence in the newest earthquake-resistant engineering techniques. This has led some seismic safety experts to suggest that Japanese engineers, whose design decisions were blamed for much of the damage in the Jan. 17 quake, are getting a bad rap.

Despite ground tremors severe enough to wreck one in five buildings in a city of 1.5 million people, many structures that incorporated modern seismic safety construction techniques survived relatively unscathed. At least 100,000 older buildings were destroyed.

“The fact is that the very modern structures which already incorporate the very advanced design features performed very well,” said Nicholas Sitar, a geotechnical expert at UC Berkeley who was dispatched to Kobe by the National Science Foundation.

Based on their observations, several dozen earthquake engineers and seismologists, interviewed in Japan and the United States, said housing construction, highway design and bridge reinforcement in California--where engineers have taken a fundamentally different design approach to many seismic safety problems--offer a much greater safety margin in a major quake.

But the thousands of deaths and widespread devastation among Kobe’s older homes and businesses, which made up the bulk of the densely populated area, raise troubling questions about the pace of retrofitting vulnerable buildings, transportation routes and utility pipelines in many areas of the United States that face the possibility of a significant quake.

“My lesson from Kobe is a scary one,” said Mete Sozen, a Purdue University expert on earthquake-resistant construction.

“They were trying to get rid of their vulnerable construction in an orderly manner . . . as quickly as they can,” he said. “I say these people were ahead of us--doing their level best--and they got their teeth knocked in.

“The earthquake arrived before their resources were in place. Our investment in trying to lessen our vulnerability is anemic compared to theirs, and that is what drives me to despair.”

Geoffrey R. Martin, chairman of USC’s civil engineering department, agreed. “It is not that we don’t understand the problem,” he said. “The question of retrofitting is a question of time and money and political will.”

As the world’s third major urban temblor in six years, the Kobe quake is prompting an anxious reassessment of U.S. seismic safety practices. Even states usually untroubled by earthquake fears, such as Illinois, Massachusetts, Missouri and Arkansas, are already quietly strengthening interstate highways and key bridges against the possibility of a serious temblor.

Still rebuilding from the 1994 Northridge earthquake and the 1989 Loma Prieta earthquake, California is well into its own sober reassessment of such risks and how best to protect lives and property.

Unwilling to wait months for the formal reports by Japanese authorities, U.S. engineers and seismologists are formulating the lessons of Kobe, based on firsthand inspections and detailed eyewitness reports from returning scientists.

They are the kind of international tourists no Chamber of Commerce wants--gaping at the city’s leaning towers and studying its crumpled quilt of ruptured highways, buckled wharves and splintered homes. Some are structural engineers from California; others are soil specialists from New York, seismic safety experts from Illinois and geologists from Texas.

Civil engineering professor Yan Xiao, nursing the cold he caught hiking through Kobe’s ruined port, fanned out his collection of photographs like playing cards on a USC conference room table.

Xiao stared solemnly at the color images of cracked bridge columns, tilted retaining walls, ruptured asphalt and collapsed highway decks.

“We have a lot we can learn,” he said.

Some Northridge Areas Were Hit Harder

Despite initial reports to the contrary, some areas hit by the Northridge earthquake experienced stronger shaking than did Kobe, according to Hiroo Kanamori, director of Caltech’s seismological laboratory. Yet Kobe suffered at least 10 times the damage, and the death toll exceeds 5,200.

The newest estimates suggest property damage and economic losses may total more than $200 billion, making the 6.8 Kobe quake--a moderately strong temblor as measured by technical magnitude--the most expensive natural disaster in modern history.

Experts in urban vulnerability, such as Barclay Jones at Cornell University, explain that the epicenter of the temblor was near the heart of one of the 10 largest urban “mega-cities” in the world--a densely built-up area, where elevated highways and railways are the norm.

The 6.7 Northridge earthquake was a suburban disaster in an area of comparatively low population density. With buildings more widely separated and with more room for surface transportation lines, individual structural failures during the quake were not as likely to trigger a chain of collapses.

“Land values have gotten so extraordinarily high in Japan that open spaces are virtually nonexistent,” Jones said. “If you look at the region within the damage area for Northridge, there are substantial areas that have no population at all.”

The hazard faced by Kobe residents was compounded by three factors of particular importance to California seismic safety experts: the powerful amplifying effect of weak soil and landfill throughout the area, substandard residential construction, and relative inattention to the potential for a major quake on a minor fault.

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It is now believed that the single most pervasive cause of damage in Kobe was the treacherous soil on which the city and its harbor were built.

Like many sections of metropolitan Los Angeles, Portland, Seattle and the San Francisco Bay Area, Kobe is built on loosely compacted sand and river sediment, with portions of artificial landfill and reclaimed marshland.

Violent shaking robbed the ground of its strength, turning moist sandy soils and landfill to quicksand--a process called soil liquefaction. The sandy sediments also amplified the ground shaking in many areas so that it lasted twice as long as the Northridge temblor, engineers said.

“One of the differences here from Northridge is the larger extent of ground failure,” said L. Thomas Tobin, executive director of the California Seismic Safety Commission as he inspected the damaged areas:

“In Northridge, we had to look for it. (In Kobe), it is almost everywhere.”

The fault that ruptured in Kobe apparently focused its violent energy at the region’s weakest soils, unlike the Northridge temblor. Its most destructive energy was pointed away from most potential quagmires in areas of the Los Angeles Basin and the San Fernando Valley.

U.S. experts in Kobe have inspected nine miles of berths and other port facilities where the ground shifted so much that retaining walls were shoved up to 30 feet into the harbor, while land behind the walls sank as much as nine feet--paralyzing one of the world’s largest container ports for what is expected to be years.

Acres of asphalt buckled, swallowing trucks. Giant cranes were derailed or broken. More than 110 shipping containers fell into the sea.

Since the early 1980s, engineers have developed several ways to prevent soil liquefaction, but much of the port was built before the techniques were developed.

“The whole place looked like a swamp,” said earthquake expert Leslie Youd at Brigham Young University, who inspected the liquefaction damage in Kobe.

Harbors in Los Angeles and the San Francisco Bay Area are built on artificial islands and landfill areas, making them--and the pipelines, roads and railways that tie them to the mainland--vulnerable to the kind of severe soil subsidence that crippled Kobe.

The twin ports of Los Angeles and Long Beach, which are undergoing ambitious expansion programs, make up the largest container-shipping facility in America.

At the Port of Los Angeles--midway through the largest harbor expansion in the United States--officials say they are building seawalls, new artificial islands and container berths to easily withstand the kind of earthquake that in seconds turned Kobe’s port into a quagmire of buckled wharves, rails and asphalt.

“You never want to be smug about an earthquake,” said Worldport L.A. harbor engineer Dick Wittkop, “but our structures should quite easily ride out a big event.”

Harbor officials said that since 1981 they have replaced 70% of the wharves and container berths with more quake-resistant structures, using a design that has proved its worth by safely riding out the shock waves in Oakland harbor during the Loma Prieta quake.

“I would expect in Kobe that the ground accelerations in the port would be much higher than in the Port of Los Angeles because of the soil. They are sitting on mud which considerably amplifies the shocks. We are not,” he said.

Independent experts say these advanced construction techniques at those ports have stabilized the landfills and harbor walls more effectively and make any such earthquake damage less likely. But they acknowledge that they are still assessing the risk, including a re-evaluation of the Vincent Thomas Bridge that leads into the harbor area.

“The Port of Los Angeles uses a form of construction that is inherently more stable than in Kobe,” said USC’s Martin. “A lot of attention is being paid to the design of dikes and wharves so that the port could stay operational even in a Kobe-type quake.”

Pattern of Damage Not Easily Explained

Not all the damage in Kobe can be as easily explained. On some blocks, old buildings remained intact, while newer, multistory structures shook free of their concrete and stone exteriors, showering sidewalks with lethal debris.

Some of the destruction was caused by the complicated interplay of soil types and foundation construction; other damage was caused by poor welds and inferior steel bolts. Even the proximity of adjacent buildings sometimes meant the difference between serious damage and minor wall cracks.

Shifting soils and ground deformation undermined some of Kobe’s newest, and theoretically most quake-resistant, structures.

Just before the quake, for example, road builders had finished an expressway from Osaka to Kobe and its industrial offshore islands. A thing of beauty, it had the massive, quake-resistant supports of which the Japanese engineers were so proud.

But in the quake, the deck slid right off the supports upon which it rested and the roadway collapsed for several miles.

Neil Hawkins, a University of Illinois earthquake engineering expert who has worked extensively in Japan, noted that the surface over Kobe’s new subway lines, where land had been backfilled after tunnels were excavated, had sunk as much as nine feet for miles along the new routes, with underground stations also sustaining serious damage.

Peter Yanev, director of the firm of EQE International, which advises business and government agencies on quake damage, said the way in which buildings near the bay had simply leaned sharply to one side in the soft soil as the ground settled showed that engineers don’t yet know how to build safely on such unstable soil.

“The biggest lessons of the earthquake as far as I am concerned is that we have too many (unfounded) assumptions about soft soils, and this is directly pertinent to many California locales,” Yanev said.

But even where soil subsidence was its worst, portions of an elevated monorail survived intact because its foundation pilings had been set deeply enough to withstand the earth shifting around them, other experts said.

Modern homes, bolted to new cross-braced, continuous-footing foundations for greater stability, withstood the kind of soil deformations that destroyed thousands of older residences.

“High-rise buildings on deep pilings or with deep foundations also appeared undamaged,” Youd said.

Today, engineers in the United States and Japan use a variety of engineering techniques that can alleviate the hazards of soil liquefaction. The suspect ground can be thoroughly compacted with vibrating probes, or special columns of crushed stone can be inserted to stabilize the soil.

“We are learning by trial and error, but we do have methods to mitigate the liquefaction problem,” said Stephen E. Dickenson, an expert on soil liquefaction at Oregon State University.

“It becomes a matter of expense and economics. Can we afford to address the entire issue in the next five years, or even in the next 25 years?”

Miles of Water, Gas, Sewer Lines Damaged

Visiting engineers and earthquake experts also found hundreds of miles of water, gas and sewer pipes in densely populated areas so badly cracked or broken that rebuilding them may take the rest of the decade.

The result is that even where buildings survived without significant structural damage, they remain unusable for lack of heat and working plumbing.

Fractured gas lines fueled fires, despite automated shut-off systems developed by Japanese utilities. With broken mains and few emergency water supplies, firefighters were hard-pressed to control the blazes.

As a consequence, there were more than twice as many fires in Kobe--about 300 serious ones--than after the Sylmar quake in 1971 or after the Northridge quake, U.S. experts said.

To avoid the problems caused by Kobe’s pipelines, engineers said, utilities need to develop more highly computerized safety features. Experts said that the development of a “smart” system operated by gas and water companies to analyze in a few seconds the pattern of breaks and to select a means of controlling and isolating them is an essential reform for California.

Such systems are still on the drawing board.

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Perhaps the most striking difference between Kobe and American cities prone to quakes has little to do with the high technology of earthquake engineering or sophisticated seismology.

It involves the more fundamental matter of housing construction.

In Kobe, as in many areas of Japan, older homes use a wooden post-and-beam construction style. Vertical posts brace long horizontal roof beams, with little or no reinforcing. The traditional roofing is heavy terra cotta tile, which is good for preventing typhoon damage but adds to the structure’s inherent instability. Only the most expensive homes incorporate seismic safety features, engineers said.

By contrast, the wooden frame of an average American home is cross-braced with studs and lightweight plywood shear panels or drywall panels. Roof, walls and foundation are usually tied together.

The result is a structure that bears up remarkably well even in the severe ground shaking of a serious quake.

“Both Northridge and Kobe occurred early in the morning,” said Dave Wald, a seismologist for the U.S. Geological Survey. “In Northridge, where the houses are well constructed, home was probably the safest place to be; in Kobe, that was probably the worst place to be, because of the weak construction.”

It may be months before any definitive engineering report on Kobe is ready. No one is certain how much hidden damage there may be in high-rise buildings or to subsurface utility systems.

Although much has been made of the differences in Japanese and U.S. engineering approaches to earthquake mitigation, they have more in common than ever. And after Kobe, both governments formally agreed to share the lessons that urban quakes are teaching those who live within their reach.

Underlying all the debates over which engineering precautions are most effective is the question of where such resources should be marshaled most effectively.

As Los Angeles learned--and Japan now has been taught--earthquakes occur where they are least expected--often on faults seismologists never even identified before their destructive force was unleashed.

Until Kobe, the Japanese invested their greatest mitigation efforts in Tokyo, where they have spent billions of dollars bracing for a recurrence of a major disaster like the 1923 earthquake that killed more than 140,000.

Kobe was, almost literally, the last place in Japan they expected a serious temblor.

“Even if you don’t know where the next earthquake is coming from,” said Oregon State University geologist Robert Yeats, “you have to focus your resources where the people are.”

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The Lessons of Kobe

Despite stringent building codes, many highway overpasses, bridges, homes and high-rise buildings collapsed during the 6.9 earthquake in Kobe, Japan on Jan. 17. Here is a comparison of geological conditions and building techniques in Kobe and the Los Angeles area.

Liquefaction Danger Areas

The port of Kobe, like the Los Angeles-Long Beach port area, is a major Pacific Rim shipping center. But liquefaction--when shaking soil becomes jelly-like--is a major concern in Kobe, as it is in much of coastal California. Ground failure heavily damaged Kobe’s maritime facilities and contributed to widespread destruction of utility pipelines, elevated highways and bridges.

What Happened in Kobe

HIGHWAYS: The ground shaking exceeded design limits by so much that hundred of support pillars were seriously damaged. Four railways and three major highways were cut. The repair bill may total $50 billion.

STEEL-FRAME BUILDINGS: Most newer high-rise buildings appeared to withstand the shocks, while pre-code buildings collapsed in many cases. It may be many months before inspections are complete.

WATER AND GAS: Miles of water, sewer and gas pipes broke. That, compounded with Kobe’s high population density, resulted in 300 fires, twice as many as occurred after the Northridge earthquake.

ROUTINE RESIDENTIAL CONSTRUCTION: Thousands of homes simply collapsed, killing or injuring the occupants.

PERSONAL READINESS: Few people seemed to have personal earthquake preparedness kits with emergency food, water and medical supplies.

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Japan’s Preparations

More than 200,000 special gravel drains and buried stone columns installed in the past 20 years help stabilize landfills and artificial harbor facilities. These minimized damage in limited areas where they were placed.

HIGHWAYS: Huge, brittle bridge and highway supports are designed to withstand supports are designed to withstand shaking at about one-third the force of gravity. In the Kobe quake, the force exceeded that amount and many pillars snapped.

STEEL-FRAME BUILDINGS: High-rise buildings constructed since 1981 incorporate flexible design meant to safely absorb seismic energy, but are still stiffer than in California. A new low-rise building in Tokyo might use twice as much reinforcing steel as the same structure in San Francisco.

WATER AND GAS: Japanese utility companies had developed what they believed would be an automatic cutoff system to safely shut down natural gas lines in the event of a serious earthquake.

ROUTINE RESIDENTIAL CONSTRUCTION: Traditional Japanese housing relies on a frame of a few large posts topped by a heavy tile roof, with no cross-bracing.

PERSONAL READINESS: In Japan, there are annual earthquake drills, but fewer than 30% of the people in Tokyo participated in last year’s exercises; fewer than 10% in Kobe participated.

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California’s Preparations

Many new construction projects make use of special soil compacting techniques, but older landfill areas, such as Venice and San Francisco’s Marina District, remain vulnerable.

HIGHWAYS: Highway engineers emphasize smaller, more flexible supports than can sway with ground shaking up to 70% of the force of gravity without breaking. In the Northridge quake, shaking exceeded 1g (100% of the force of gravity) in some areas.

STEEL-FRAME BUILDINGS: Flexible-frame design is favored. After the Northridge quake, structural engineers found dangerous cracks in more than 120 steel-frame buildings. The newest buildings with shock-absorbing foundations, called base-isolation systems, emerged without damage.

WATER AND GAS: Unprotected oil and gas lines, along with sewer and water systems, remain a major concern.

ROUTINE RESIDENTIAL CONSTRUCTION: In California, average housing uses cross-braced, stud-wall construction, with plywood shear panels lending lateral strength.

PERSONAL READINESS: For all practical purposes, formal emergency drills in businesses and schools are nonexistent. However, personal earthquake kits are increasingly common in California homes and work places.