THE LOS ANGELES EARTHQUAKE : New Stress on Old Buildings Increases Risk for Next Time

The good news, structural engineers said Thursday, is that most of Greater Los Angeles’ old, risky brick buildings--more than 7,500 in all--held up fairly well against the 6.1 quake.

The bad news, they said, is that the buildings that held together this time are more susceptible to shake apart next time.

“Every time we have an earthquake, they’re weakened,” explained Donald Hubka, a senior Los Angeles city building inspector. Beyond the obvious--wall fractures, foundation slippage, broken chimneys--the quake leaves a barely perceptible strain on the structural integrity of buildings. The region’s unreinforced masonry buildings thus remain the greatest threat to life in the event of a cataclysmic quake.

Thursday’s temblor served to illustrate the jeopardy posed by the unreinforced masonry buildings, most of which predate structural codes adopted after the 1933 Long Beach earthquake.

Whittier Buildings Fall

In Whittier, the old community located closest to the quake’s epicenter, three buildings incurred a total collapse, while eight to 10 more were damaged beyond repair. Most were two-story commercial buildings located in the town’s historic “Uptown” commercial district. Damage was still being assessed at many more, and police estimated at least 50 commercial buildings and 100 homes were extensively damaged.

All of the buildings were constructed of unreinforced masonry, said Sonny Morkus, the city’s emergency response coordinator.

“We were lucky,” Morkus said. If the quake had hit at noon instead of 7:42 a.m., “we could have had a hundred injuries, and probably several deaths.”

Throughout the region, the damage could best be measured by the impact on unreinforced brick buildings.

Damage in East L.A.

The county Building and Safety Department recounted several damage reports in East Los Angeles, said spokeswoman Roslyn Robson. Seven buildings were posted as unsafe to occupy, including five commercial buildings (four on Whittier Boulevard), a one-story adobe church and a two-story apartment building at 834 Indiana St.

In the City of Los Angeles--which by itself has more than 7,000 unreinforced brick buildings--Hubka estimated that inspectors might receive calls to check for damage in as many as 200 buildings in the coming days.

As of 2 p.m. Thursday, inspectors had visited 30 to 40 buildings, said Carl Deppe, assistant chief of the earthquake division of the city’s Building and Safety Department. Five buildings had been ordered vacated, including one “artists-in-residence” loft building at 900 1st St. The other buildings were commercial structures.

Buildings May Be Razed

“The damage was severe enough that we were worried that in an aftershock there would be more damage,” Deppe said. The buildings would remain vacant until judged safe, perhaps after reinforcement. They could also be subject to demolition.

Deppe said the early reports indicated that city’s stringent seismic strengthening ordinance--enacted in 1981 to guard against loss of life in a major temblor--was proving of value.

Under that program, 1,000 buildings have been significantly reinforced. All unreinforced masonry buildings are supposed to be buttressed or demolished by 1992, with residential structures being phased in first. Deppe said minor damage was found at a few of the reinforced buildings.

“It sounds like it’s working pretty well,” Deppe said. “Nevertheless, we plan to take a closer look, see if there might be any problems.”

Much of the damage is cosmetic, Hubka said. Signs of true danger are usually obvious, such as separations between walls and ceilings and severe wall cracks, he said.

In citywide terms, Hubka said: “I’m surprised we don’t have more damage than we do. I was expecting a lot more.” Another potential trouble spot located farther from the epicenter is UCLA, which had several buildings judged seismically unsafe in a state survey. But officials there reported no damage.