The University of California's release of data on nearly 1,500 older concrete buildings across Los Angeles marks a key step in the city's efforts to improve earthquake safety.
Now the hard part begins.
UC researchers spent several years compiling the list of buildings, a first-of-its-kind effort to help identify a type of building that earthquake experts have long said poses the greatest risk of death.
Of all the older concrete buildings in Los Angeles, the researchers estimated that only about 75 would collapse during a huge quake.
But determining which ones are structurally at risk will require individual inspections.
Experts say the cost for just a preliminary examination could range from $4,000 to $20,000, depending on the size of the building. Retrofitting problem buildings would cost property owners much more, from the tens of thousands of dollars to perhaps more than $1 million for large office or residential towers.
The list underscores the scope of the challenge: More than 220,000 people live or work in the listed buildings, according to a Times analysis of the researchers' data.
For city leaders, the next step is deciding how to inspect and repair the buildings — and who should cover the costs. Mayor Eric Garcetti has said getting quake-vulnerable concrete buildings retrofitted is a top priority and partnered with the U.S. Geological Survey to make recommendations on how to get it done.
Some City Council members have been exploring the idea of a state bond initiative to help defray some of the costs for building owners.
The University of California sent the list of addresses to the city Tuesday, after Los Angeles officials had asked for it. After months of debate about whether to make the list public, UC provided a copy to The Times in response to a public records act request.
The release of the list moves Los Angeles closer to addressing the dangers of concrete buildings after four decades of inaction.
Earlier efforts to identify and fix problem buildings died amid opposition from property owners after the 1994 Northridge quake. Concrete buildings collapsed during both that temblor and the 1971 Sylmar quake, in which hospital buildings crumbled, killing about 50 people.
Concrete buildings can be particularly vulnerable when they lack adequate steel reinforcement. As a result, their frames are brittle and can crumble during heavy shaking. Concrete buildings are found across Los Angeles but particularly in older commercial districts such as downtown, Hollywood and Mid-Wilshire. A Times survey last year found heavy concentrations of concrete residential towers and office buildings in those areas as well in Westwood and Encino.
Los Angeles is now the first city in California with a public list of older concrete buildings, and seismic safety experts said they hope this raises awareness of the issue.
"This challenge our communities face is now out in the open … and tells the community that something needs to be done," said Craig Comartin, a structural engineer and past president of the Earthquake Engineering Research Institute, based in Oakland.
Some Los Angeles officials said the city must act by determining which buildings are actually at risk.
"We need to ensure that, as best as we can, that our residents are safe," Councilman Bernard C. Parks said. "It's absolutely important."
Councilman Mitch Englander said the UC researchers' work gives the city a rare opportunity to move forward, saying the city did not produce a list on its own "because of the political fallout, quite frankly."
"What do you do with it, once you have it? That's the million-dollar question," he added.
Business groups and property owners have long opposed mandatory retrofitting, saying they cannot shoulder the costs alone.