Fifteen years after the Northridge earthquake exposed the dangers of certain “soft-story” apartments, only about 800 of the 20,000 such structures in Los Angeles have been retrofitted, according to city records.
The pancake collapse of the Northridge Meadows apartment complex, which killed 16 people, was one of the most dramatic images of the Northridge earthquake on Jan. 17, 1994. But despite concern at the time that these multi-unit buildings with weak ground floors posed a critical risk, progress inspecting and fixing these older buildings has been slow.
Only one county and about a dozen cities, including Los Angeles, have even begun to address soft-story buildings, according to the state Seismic Safety Commission. Fremont, which straddles the Hayward fault in Northern California, appears to be the only city in the state actively mandating retrofits of this kind of apartment building.
“It’s an issue we need to go back and address again,” said Los Angeles Councilman Greig Smith, who represents an area that includes Northridge. As a councilman’s aide, he helped pass a city ordinance encouraging voluntary retrofits soon after the quake.
“It was a partial fix, and there needs to be a complete fix,” Smith said. He hopes to start discussions later this year about whether Los Angeles should have a mandatory retrofit law.
Seismic experts have been concerned about soft-story buildings -- in which open layouts and a lack of walls add up to meager support on the ground floor -- since the 1971 Sylmar earthquake, said Fred Turner, a structural engineer with the Seismic Safety Commission.
In the 1980s, new building codes required stronger structural supports on new construction.
But the Northridge earthquake was a stark reminder of the dangers still facing existing buildings.
The temblor hit these types of buildings hard. Some, such as apartment buildings constructed in the postwar years in suburban areas across Southern California, collapsed.
One of the critical problems with Northridge Meadows -- in addition to construction deficiencies -- was a design that tucked parking under the inhabited floors.
Putting parking spaces or big windows on lower floors meant that upper floors were suspended above long, open areas instead of rigid walls. The spindly posts often propping up the lower floors proved to be no match against heavy, swaying upper stories.
In the case of Northridge Meadows, the magnitude 6.7 temblor caused the second and third floors to crumple right down onto the lower floors, leaving some cars poking out of the sides of the buildings. Its collapse caused the largest number of deaths in a soft-story building. The 16 people who died were on the first floor.
After the quake, the Seismic Safety Commission recommended that addressing existing buildings that were vulnerable in earthquakes should be one of the state’s highest priorities. Soft-story buildings were considered one of the vulnerable types of buildings.
“I think history would say the government got cold feet over that,” Turner said. “We’re certainly on the slow track.”
Much of the issue is the cost of retrofits, experts said. Even if landlords make the buildings safer, tenants might refuse to help defray the costs by paying higher rents. Fremont sent letters out to 28 apartment building owners in 2007, the year its requirements went into effect. The building owners have until 2010 to apply for permits, but only two have begun or finished retrofits.
“There’s some disappointment, but you’re asking people to spend money,” said Alan Wong, supervising building inspector for the city. “Bottom line is, people don’t like to if they don’t have to.”
While looking at ways to help defray the cost, such as offering low-interest loans or seeking federal assistance, several cities are considering requiring the retrofits to improve the response.
In Berkeley, where the city requires structural reports on soft-story buildings, only about half of the 320 multi-unit buildings with soft first stories have filed reports or applied for permits to retrofit the buildings within the mandated two-year window.
“That’s pretty good, but obviously we want everyone to comply,” said Dan Lambert, manager of the soft-story program for Berkeley. “We think to have an effective program, you need a mandatory program.”
Lambert pointed to the success of mandatory requirements in some cities for unreinforced brick buildings, which many experts consider the most dangerous in earthquakes. In those locations, about 87% of these buildings have been retrofitted or demolished.
Bob Steinbach, a spokesman for the Los Angeles Department of Building and Safety, said his department was not ready to endorse any changes. Although only 4% of the soft-story buildings have been retrofitted, an unknown number have been demolished, diminishing some of the risk to tenants, he said.
“It’s important to remember that, in ’94, not all soft-story structures sustained damage,” he said. “Right across the street [from Northridge Meadows] there was a soft-story building that barely even cracked windows.”
In the meantime, earthquake scientists at the U.S. Geological Survey advised people to ask landlords about structural studies and pick apartments where they feel safe.
“There’s an assumption that the government doesn’t allow really unsafe things to be around, but the government can’t force us to do things to our own house,” said seismologist Lucile Jones. “It’s a consumer choice. . . . Unless you’re in a building built to the latest codes, you’re not as safe as you could be.”
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What is the danger of a “soft-story” building?
Apartments and condominiums with parking or commercial space on the first floor are prone to collapse if ground-floor walls and columns are not strong enough to hold up the building during earthquakes.
Source: Seismic Safety Commission