At LAist, we've thought a lot about how to motivate people to prep for the massive earthquake that's inevitable here in Southern California. We even dedicated an entire podcast to it.
We teamed up in 2021 with our friends at the L.A. Times to push Southern Californians to get ready. You can watch that virtual event covering the basics of quake survival. We've also gathered the best of our coverage in a no-nonsense guide to getting ready. No more excuses. Let's do this.
City National Plaza in downtown Los Angeles is surrounded by chaos. Honking cars, bike messengers, a tractor moving dirt from one pile to another.
Towering above it all are two massive buildings that have been around since the 1970s. Originally known as the ARCO Towers, the buildings are now labeled City National Bank and Paul Hastings — two 52-story giants, some of the tallest in L.A., clad in shiny green-brown stone, filled with workers, appearing unmovable against a bright blue sky.
Like thousands of other buildings of all sizes across Southern California, these towers were built using a method known as welded steel moment-frame construction (WSMF), which was popular from the 1960s through the early 1990s.
It was believed to be, as FEMA later noted, “earthquake-proof.”
Then the Northridge quake hit.
And we stopped using it.
That’s because scientists and structural engineers who study big earthquakes now believe older WSMF buildings could collapse if the ground shakes hard enough. But little has been done to address that potential danger.
Every day, whether it’s at home or at work, Southern Californians walk into buildings with the assumption that they’re going to be OK if an earthquake hits. That’s essentially what our building codes are designed to do: keep walls standing, roofs intact, and people feeling safe. The goal of current codes is to ensure any damage is survivable — that we’ll make it out once the shaking stops.
With every major earthquake that rolls through, we find new problem areas, and if they’re bad enough, we usually adjust.
In 1933, for example, Long Beach was hit hard by a 6.4 magnitude quake; 120 people died. More than 100 schools in the area were damaged and 70 were destroyed. If the quake had struck during school hours instead of the evening, thousands of school children could have been killed as well. In response, California passed the Field Act, which required schools to meet certain levels of earthquake-resistant construction.
The 6.6 San Fernando quake, in 1971, led to an overhaul of hospital building codes after Olive View Hospital in Sylmar collapsed, killing 64 people. In that case, the concrete structure lacked sufficient steel reinforcement. It took decades, but eventually mandatory retrofit programs were put in place to strengthen those types of concrete buildings.
The 6.7 quake that hit Northridge in 1994 exposed a vulnerability in what are known as soft-story structures, which often have parking tucked under the first floor. At the Northridge Meadows apartment complex, the poles holding up the first stories gave way as the ground moved, turning three-story buildings into two, killing 16 people.
Again, decades later, L.A. instituted a mandatory retrofit program for the “most vulnerable buildings,” which is still a work in progress. A report issued this month by the City of L.A.’s Department of Building and Safety puts the number of soft-story structures that still need to be retrofitted at more than 4,500.
[NOTE: Search to see if your building is under any retrofit requirements here]
Some of the first hints that buildings constructed with WSMF connections might be vulnerable came shortly after the 1971 San Fernando quake.
One clue came from investigators from the Pacific Fire Rating Bureau, an insurance-industry association, who went out to inspect the ARCO Towers in downtown L.A., which were still under construction.
As they wrote in a report issued in August 1971, “a 25% increase in the number of cracks in the welds in the lower two stories of both steel framed towers was found after the earthquake.” While they couldn’t blame the cracks on the quake with certainty, they did note that the damage was “seemingly due to the earthquake,” adding that the damage was “disquieting.”
In the end, the welds were fixed at a cost of $400,000, or $2.5 million in today’s dollars, and the buildings were completed.
By then, WSMF construction was the preferred method for high-rises in the U.S. That’s because steel is strong and ductile.
Structural engineer Swaminathan Krishnan, who used to work at the California Institute of Technology (Caltech), explained ductility to me this way: “If you take a steel wire and try to go back and forth, you cannot break it. It will be able to go through large cycles, back and forth, before it actually snaps.”
Essentially, steel absorbs energy in a way that allows it to flex and sway rather than break. Ductility, said Krishnan, is “good for an earthquake, because an earthquake is going to shake your building back and forth several times.”
Of course, the framework of one of these buildings isn’t one solid piece of steel. A building’s skeleton has joints, where giant beams are bolted and welded together. Those connections also need to withstand shaking to keep the building structurally sound.
That’s why insurance investigators examining the ARCO towers worried not only about the cracks they found in 1971, but also about the implications for other welded steel-frame structures.
Despite their concerns, WSMF buildings wouldn’t come under hard scrutiny until after the Northridge quake hit, more than two decades later.
The Northridge quake shook L.A. before dawn, when most people were still in bed. In all, 58 people were killed and more than 9,000 injured.
The 6.7-magnitude quake damaged or destroyed more than 82,000 buildings. Some of the damage was obvious and dramatic, but in the days and weeks after the quake, a lot of work was done to look for less obvious problems.
Structural engineer David O’Sullivan flew down from the Bay Area to inspect a client’s WSMF buildings, which were located about 14 miles from the epicenter.
“At the time, all I knew is that we had a client that had damaged buildings. And I was going out to look at them,” O’Sullivan told me. The buildings he was there to investigate were one story and four stories high, the taller of which was less than a year old. Right away, he said he could see why the one-story building was worrisome.
“The building was actually physically leaning a little bit, about four inches out of plumb,” he said. “So you could see [it] with the naked eye.”
The four-story building looked fine at first, but then a contractor noticed some disturbances to the fluffy wool fireproofing around the building’s first floor columns. They scraped it off to get a better look.
The news was bad.
All of the connections on the second floor had sustained severe damage.
“And that was a big wow,” said O’Sullivan.
“That wasn’t the way they were supposed to behave,” he said. “Moment-frame buildings, prior to the Northridge quake, were thought to be the premier lateral force-resisting system you could have in a building. And they were going to be ductile and absorb lots of energy. And this wasn’t ductile at all, it was a brittle fracture. It was all unprecedented.”
Reports of damage to WSMF buildings came in from all over L.A.
At the time, Los Angeles had about 2,000 WSMF buildings. L.A. required the inspection of only about 200 that experienced the highest levels of ground shaking; about 30 were significantly damaged, according to FEMA.
Some retrofits followed and the damage to so many WSMF buildings quickly led to tougher requirements for steel moment-frame construction. Ultimately, engineers came up with a stronger system for connecting beams.
Six years after Northridge, FEMA issued a series of comprehensive reports. The findings were stark.
Source: FEMA
Joe Allbaugh, the director of FEMA at the time, summarized things this way: “Damage assessments after Northridge led FEMA to conclude that modern steel-frame buildings designed to sway without fracturing in earthquakes are not as safe as previously thought and may be susceptible to failure in major earthquakes.”
The implications were significant. As FEMA officials said: “Most high-rise structures built in the U.S. since 1970 use this type of construction.”
Agency officials added that widespread issues discovered with WSMF welds, “called into question all building codes developed over the previous 20 years that addressed this type of construction.”
So what has the city been doing to address all the WSMF buildings that went up in L.A. prior to Northridge — the 1,800 or so that didn’t get inspected?
“'Nothing' is the answer,” L.A. Mayor Eric Garcetti told me last year.
Garcetti said officials are looking into possible responses to the issue. Currently, the city does not require retrofits for WSMF buildings. Garcetti cited San Francisco as L.A.’s “next chapter.” San Francisco released extensive recommendations on improving the earthquake safety of its steel buildings late last year, making it the first city in the nation to do so. The report found tall steel buildings were a particular concern.
Source: City and County of San Francisco Office of Resilience and Capital Planning
Krishnan, the structural engineer, said he’s been paying attention to the safety of WSMF buildings since the 1990s. He was working at Caltech in the 2000s when he focused on research looking into what could happen to steel-moment buildings in a big earthquake. A 2008 report called The ShakeOut Scenario, issued by the U.S. Geological Survey, relied on Krishnan’s research.
The ShakeOut looked at a hypothetical but devastating scenario: the fallout from a 7.8-magnitude earthquake on the Southern San Andreas fault. The report contains a lot of eye-opening findings, including the startling estimate that as many as five WSMF buildings in Southern California could potentially collapse.
Krishnan told me how the collapse of a steel-moment building could look and sound:
“The rolling kind of waves will come in,” he said. “And they will go up the building. And the building will start shaking. Back and forth, back and forth...You’ll hear a lot of noise. Much of that noise is going to be things falling. Things rattling. But you might start to hear lots of pops. And these pops are the connections perhaps fracturing...the building might come pancaking down. That’s one possibility. The other possibility is the upper stories tilt and fall over, leaving this little stub piece sticking out of the ground.”
While Krishnan's simulations have shown that WSMF buildings can collapse if the ground motion is high enough, we’ve never seen one in the U.S. collapse in real life.
But non-WSMF steel buildings have. In 1985, a steel high-rise in Mexico City crumbled in an 8.0 quake, killing scores of people. And in 1995, a high-rise partially pancaked in Japan’s 6.9 Kobe earthquake.
Southern California hasn’t had an earthquake as big as the one modeled in the ShakeOut scenario since the 7.9 Fort Tejon quake in 1857, long before high-rises existed.
But a monster quake will happen. Paleoseismologists have dated broken layers of earth at the San Andreas Fault to determine how often big earthquakes have occurred over the centuries.
According to the ShakeOut report, “The southern San Andreas Fault has generated earthquakes of ShakeOut size on average every 150 years — and on a portion of the fault that ruptures in the ShakeOut Scenario, the last earthquake happened more than 300 years ago.”
That means another big one could come at any time.
“There’s no likelihood of it not happening,” said seismologist Lucy Jones, one of the lead authors of the report. “We’re not stopping plate tectonics. The details may change, but the earthquake is 100 percent inevitable. Just give it enough time.”
At what point do we take extraordinary steps to protect against some future disaster?
That’s a question that dogs policy makers, engineers and property owners. Mandatory retrofit programs come with high political and economic costs. Consider this: It took more than 20 years for L.A. to require soft-story buildings to be retrofitted — even after the collapse of such buildings killed people in the Northridge quake.
As of now, the collapse of WSMF buildings in an earthquake remains hypothetical.
“I’d be a fool to say nothing could ever happen,” said structural engineer David Bonowitz, who worked on the post-Northridge FEMA reports. “The question is whether that damage is the kind of collapse level damage that normally gets us worked up to the point where we have mandatory retrofit programs. I’m not seeing that yet.”
There is not, in fact, widespread consensus that these steel-frame buildings are high-risk enough to justify inspection and repair.
Inspecting WSMF buildings — nevermind fixing them — is a costly task.
O’Sullivan told me that, just to figure out if welds are compromised, the ceiling, sheetrock and fireproofing need to be removed. And if retrofits need to be done, entire floors of buildings often have to be evacuated as construction takes place.
Fixing and bracing welds creates smoke, which calls for the creation of tunnels to blow exhaust out of the building. Fireproof blankets need to be laid down as sparks fly and additional workers have to stand by to make sure a fire doesn’t break out.
And then you have to put it all back together again.
Krishnan estimates that it could cost $50,000 to retrofit a single connection, and there can be dozens of them per floor, depending on the size of the structure.
“We tend to be influenced by what we experience,” said structural engineer Ron Hamburger, who reviewed Krishnan's work for the ShakeOut report. “And what we see in the United States, we've not yet seen any building of this type collapse. And so when you tell people, this is a real problem, it's not unusual for them to say, ‘Show me the bodies.’”
It’s been 18 years since FEMA’s post-Northridge report called into question a whole generation of steel-frame construction.
Which got me wondering about those “disquieting” cracks that investigators found and reported back in 1971 in downtown L.A’s twin 52-story high-rises.
Turns out the towers were not among the 200 buildings inspected after Northridge — the ones that authorities said experienced significant ground motion. I wanted to know if the towers’ owners had taken additional steps since ’94 to inspect or retrofit them.
According to the L.A. County Assessor, the buildings are owned by Commonwealth Partners, which paid $858 million for the properties in 2013. Commonwealth Partners made the purchase on behalf of the California Public Employees Retirement System (CalPERS), the largest public pension fund in the nation.
I reached out to CalPERS and Commonwealth Partners, via e-mail and telephone, to ask about the last time, and to what extent, the connections between beams had been inspected.
Commonwealth Partners declined to comment.
CalPERS also declined to comment. I sent the organization a series of public records requests seeking further information about the buildings. While they've sent some documents, they haven't yet fulfilled all of my requests.
Despite an exhaustive search, I was unable to find any publicly available permits that indicated the buildings have been retrofitted to meet post-1994 standards for WSMF structures. The structural engineers I talked to who study WSMF buildings said they lacked enough information to comment on the towers.
“To assess absolutely whether or not they are safe — no ordinary person can do that,” said Hamburger. “I mean, it takes training, and it takes extensive analytical work to figure out if a given building is safe.”
Structural engineers point out that no building will ever be 100 percent safe.
We don’t know what’s going to happen to the ARCO Towers, or any of the other steel moment-frame buildings across Southern California. They could be OK when the Big One hits.
Or maybe the ground motion, soil composition and brittle welds will cause some of them to collapse or partially collapse.
How much of a risk, as a society, are we willing to take? And once we determine that a type of building could be dangerous in an earthquake, when do we act?
I posed this question to Bonowitz, the structural engineer who didn’t think a mandatory retrofit program for WSMF buildings is necessary.
“It’s a little bit crass, but suppose I told you that 99.9 percent of anyone in greater Los Angeles is going to survive the big earthquake. Is that acceptable to you?” he asked.
I told him I thought we should probably try to do everything that we can to save every life.
Bonowitz pushed back.
“I think to posit a large earthquake in an urban environment like Los Angeles and say it’s unacceptable if anybody dies in that earthquake, I think that’s unreasonable,” he said. “Especially if you have limited public money to put toward reducing the losses.”
For Krishnan the threat is real enough that he tried to persuade his wife not to take a job in a WSMF building in downtown L.A. He declined to name the building publicly.
“I said, ‘No...why don't we look for something else?’” Krishnan told me.
His wife wanted to know why she should pass up a great opportunity to avoid being in a building that might be fine in the Big One.
“It's a great question that she's asking,” he said. “And that's the question that 99.99% of the people out there are asking.”
So did she take the job?
“No,” Krishnan said, “She did not.”
This story was originally published in January 2019 with the launch of The Big One podcast.
