BAY AREA QUAKE : Worrisome Brick Buildings Appear to Survive

Since the 1930s, engineers have believed that certain homes, apartment houses and office buildings in San Francisco would be extraordinarily vulnerable to a major earthquake. The aging, unreinforced brick buildings would have almost no chance of surviving the severe side-to-side shaking that an earthquake would bring. Or so the experts predicted.

But on Tuesday night, city inspectors began a building-by-building check in San Francisco, and initial reports indicated that the city’s shakiest structures--most of them in Chinatown and the Tenderloin district--had largely survived intact. Witnesses reported that those neighborhoods were quiet and buildings were standing with little damage apparent from the outside.

Even so, engineer John Kariotis, one of the nation’s leading experts on earthquake damage, estimated that the old unreinforced masonry buildings will “contribute to more than 50% of the damage” in San Francisco when all is said and done.

Kariotis, head of a South Pasadena structural engineering firm, said the first pictures broadcast from San Francisco show “the same kind of thing” experienced in the Los Angeles area after the Whittier quake in 1987--”a series of building fronts that fell off.

“But a lot of other things are going to be problems as well,” Kariotis said. He said he expected to see heavy damage to concrete buildings constructed in the 1950s and ‘60s, which are especially common in the San Jose area.

“In ‘87, after the Whittier quake, we had a great degree of damage to ‘tilt-up buildings,’ the typical manufacturing building--long, very large low buildings with concrete walls,” he said. “San Jose is full of them--Silicon Valley.”

In addition, Kariotis said, “It looks like they probably had a great deal of damage with . . . soil sliding caused by the earth shaking.”

Soil sliding appeared to be problem in the Marina area of San Francisco, where wooden houses are built on hillsides, he said. Soil sliding causes structural damage to homes and can cause gas mains to break, leading to fires. Indeed, fires plagued the Bay Area Tuesday night, and there were widespread reports of gas leaks.

Kariotis, who did an analysis of Candlestick Park years ago, said problems in the stadium probably will stem from the fact that it is a steel-framed structure topped with concrete slabs that form the seating rows.

“I have a suspicion that with the flexibility of the steel structure . . . the concrete is brittle . . . the brittle concrete has a tendency to break at the corners,” he said. “It’s a common kind of thing to happen.”

He said damage to such a structure can be evaluated in as little as four to six hours, and that “they’ll probably be able to open some parts of Candlestick” soon after. But because of the threat of aftershocks, “authorities are probably going to be a little bit wary about allowing it to reopen for several days.”

Kariotis and Nels Reselund, an associate in his structural engineering firm, had been working with counterparts in San Francisco recently to develop an “earthquake hazard reduction ordinance” for that city.

In 1986, the state mandated that every community with unreinforced masonry buildings survey such structures and develop plans by 1990 to improve them. But measures mandating improvements to old buildings invariably draw opposition from property owners worried about the expense.

San Francisco’s unreinforced brick structures have gone without upgrading because the city’s seismic building codes still apply only to buildings erected after 1948. There are no laws requiring owners to update buildings that went up before that. Most of the city’s unreinforced brick structures are in that category.

San Francisco officials, however, were concerned enough about the potential for disaster that they set about identifying the unsafe structures four years ago. They found a troubling 2,100 still in use, mostly in the Chinatown and low-income Tenderloin districts of the inner city. The structures included some 25,000 residential units housing more than 40,000 people.

Despite the finding and dire warnings from disaster preparedness officials, most or all of the buildings remained standing and occupied Tuesday when the earthquake hit.

Existence of the unreinforced buildings has been a touchy issue for politicians, who fear the controversy that is sure to erupt if mandated repairs lead to rent hikes or demolitions force low-income residents onto the streets.

“If a disaster strikes, we’ll say it’s terrible, why didn’t we do something?” San Francisco city supervisor Tom Hseih said a few months ago. “Until you see the blood, I guess nothing’s going to happen.”

The aging structures have almost no elasticity and are frequently held together with deteriorating mortar that disintegrates under pressure, Frank Lew, manager of San Francisco’s seismic safety program, said in an a recent interview.

“Once that happens, you’ve lost the bearing and support and the walls come tumbling down on your head.”

Los Angeles enacted legislation in 1981 requiring landlords to make their buildings structurally sound by 1992.