We survive the Big One but our buildings don’t?
When the Big One — or even just the next Northridge-sized quake — hits Los Angeles, you will probably survive it. Between existing seismic codes for new construction and the ongoing mandatory retrofitting of concrete and soft-story wood buildings in the city of Los Angeles and beyond, most buildings should withstand a catastrophic earthquake well enough for you to make your way out of the wreckage when the shaking stops.
But those standards are designed just to keep buildings from collapsing. In a major earthquake, buildings could be so badly damaged that they are uninhabitable for months — or altogether beyond repair. With hundreds of apartment buildings, offices and supermarkets out of commission, Los Angeles would be a crippled metropolis. You think we have a desperate housing shortage now? Wait until an 8.2 hits on the San Andreas fault.
In an effort to prevent catastrophic property damage, California Assemblyman Adrin Nazarian (D-North Hollywood) has introduced a bill directing the California Building Standards Commission to strengthen the building codes governing the construction of larger apartment and office buildings and some commercial buildings. Instead of being designed just to preserve the lives of their occupants, AB 1857 would require all new “engineered” buildings to be sturdy enough to function — perhaps with some minor repair — and be reoccupied quickly after a major earthquake. That means making them about 50% stronger than current standards. The new standard would apply to schools, hospitals and other public buildings only if it is more stringent than their current codes.
The proposal is one of two Nazarian bills aimed at earthquake resiliency. The other, AB 2681, would require all cities to compile a list of seismically vulnerable buildings, although it would not mandate any retrofitting.
University of Colorado at Boulder professor and engineer Keith Porter estimates in a study that even if every building was completely up to current California codes, a “Big One” (such as a 7.0 on the Hayward fault through a densely populated part of the Bay Area) could displace enough people to replicate the kind of exodus that happened in New Orleans after Hurricane Katrina in 2005.
Jones says that requiring buildings to be built strong enough to be functional adds only 1% to 2% to the cost of new construction. She bases that assumption on estimates from a number of studies by engineers, including Porter, who calculates that a tiny fraction of the costs involved in erecting a new office building stem from using earthquake-resistant materials. Increasing the resilience of those materials would not substantially increase the cost of a building, he contends.
Some representatives of trade organizations for building owners are skeptical about the low cost estimate. Nazarian should hear out their concerns and, if they’re right, come up with a more realistic projection. But while it’s important to have a clear idea of how much the bill might add to the cost of desperately needed housing and other projects, lawmakers should bear in mind the potential long-term savings in insurance premiums and disaster relief. A 2017 study by the National Institute of Building Sciences showed that every $1 spent mitigating earthquake hazards saved $3 in future disaster recovery expenses.
The bill wouldn’t mandate that new buildings be occupiable immediately after a major quake; instead, it would leave it to the Building Standards Commission to determine how soon new structures must regain functionality. It also notes that other factors may prevent buildings that comply with the new codes from being reoccupied — for example, disrupted utilities or damaged furniture.
California earthquake standard designed to save lives but not buildings. There’s a new push to do both
California’s seismic construction requirements are designed to protect the lives of those inside. But even with the most modern codes, building to the state’s minimum requirements would leave even new buildings severely damaged in a major earthquake — to the point of being a complete loss.
Earthquake experts have become increasingly concerned about this, noting that a massive temblor would leave many without homes and offices for months if not years.
When a magnitude 6.3 earthquake directly hit Christchurch, New Zealand’s third largest city, in 2011, 70% of the buildings in the central business district were damaged, but all were completely closed because it was too dangerous to be anywhere downtown.
Now, a Los Angeles lawmaker is proposing two bills that would toughen rules on how strong new buildings should be and require cities to identify existing buildings at risk of collapse.
The proposals are expected to spark a familiar debate in earthquake country over the cost and effectiveness of boosting seismic regulations. Some in the construction industry defend the current minimum building standard as appropriate.
The first bill, AB 1857, would instruct the California Building Standards Commission to increase minimum mandatory standards for most types of buildings in the state, such as apartments, office buildings and commercial spaces, but would exempt single-family houses and duplexes.
The goal is to keep new buildings usable after a major earthquake. Even if people are forced to temporarily move out, the aim is to keep damage limited so repairs can be made within days or weeks, rather than a year or more.
Nazarian said he wants the new building regulations to become effective in 2023 as part of a scheduled update of the California Building Standards Code.
Seismologist Lucy Jones, formerly a science advisor for risk reduction with the U.S. Geological Survey, has been a big advocate of increasing California’s minimum building standards. Construction costs would only rise 1% to 2%, Jones said, citing an estimate from Keith Porter, a University of Colorado Boulder research professor.
Under existing building rules, a large earthquake could render unusable so many housing units that it would trigger a mass exodus much like New Orleans suffered after Hurricane Katrina, Porter wrote in a report.
“We want a resilient society. But we can’t have that if our buildings are not operational after an earthquake,” Porter said in an interview. “If you can’t go back into your building after an earthquake, it’s a disposable building.”
The state’s building codes allow for as much as a 10% chance that a new building will collapse in the maximum credible earthquake, Jones said.
“When you look at the economic disruption…it means tenants can’t go to work, it means neighbors who can’t use their buildings, it potentially means people don’t have a home, and it leaves businesses who don’t have workers,” Jones said. “The financial consequences land on all of society.”
Representatives of the California Building Industry Assn., which represents construction companies, cast doubt on whether tougher mandatory minimum building rules were needed for the entire state.