Ten years after the Northridge earthquake -- the costliest temblor in the state’s history -- California has made extensive safety improvements but remains unprepared for a great quake, experts say.
The California Department of Transportation has retrofitted 2,174 bridges and overpasses statewide since the 1994 quake caused portions of three freeways to collapse. The agency has just 20 to go in its retrofitting project.
Caltrans and the Golden Gate Bridge and Highway Transportation District are well along with $6.6 billion in projects on San Francisco Bay toll bridges -- to either retrofit them or build new, safer spans.
In the city of Los Angeles, 99% of the unreinforced masonry buildings -- 8,210 structures -- have been retrofitted or demolished. Most older steel-frame buildings, however, have not had their welds redone, even though welds failed in about 200 such buildings because of the Northridge quake.
Los Angeles now has “some of the most vigorous codes of any jurisdiction in the U.S.,” said Andrew Adelman, general manager of the city Department of Building and Safety. “But are the buildings in the city earthquake-proof? They are not; no one can be.”
Overall, “I think the state is significantly safer than 10 years ago,” said Ronald O. Hamburger, one of California’s most prominent earthquake engineers.
But despite those signs of progress, many experts say the state is not fully prepared for the dangers of a great quake.
“There have been huge improvements since Northridge, but we have a bad situation with unreinforced masonry buildings in many areas -- and a bad situation with buildings built according to weaker codes that are 20 to 40 years old now,” said Bruce Clark, a geologist who chairs the state Seismic Safety Commission.
Indeed, the only deaths in last month’s San Simeon quake occurred when a masonry building that had not been retrofitted collapsed, crushing two women in a cascade of bricks as they fled a dress shop.
“We have to keep pushing on hospitals and schools,” Clark said. “It’s very expensive, but it’s the only way I can think of to lower the risk in the future in these big earthquakes.”
The perennial problem in California, some seismic experts say, is that advances in quake safety are often counterbalanced by undone or incomplete efforts.
Although new buildings statewide must meet upgraded construction codes, proposals to require the retrofitting of thousands of vulnerable older structures have frequently been stymied politically. Deadlines for some projects, such as upgrading hospital safety, have been extended five years to save money in the short term.
A state survey of more than 9,000 non-wood-frame public school buildings said that only 2,122 of them “are likely to perform well and are expected to achieve life-safety performance in future earthquakes.”
An additional 7,537 buildings “are not expected to perform as well,” the survey said.
Of the $4.7 billion said to be needed to improve the safety of those buildings, not a cent has been appropriated. The survey, released in 2002, did not cover private schools, which are not under state earthquake regulation.
Projects to prevent damage from future quakes have also lagged as the Federal Emergency Management Agency has cut back money and drawn limits on aid to the state, counties and municipalities to retrofit major buildings, such as the County Hall of Administration in downtown Los Angeles.
And only about 15% of California homeowners carry earthquake insurance, compared to 30% a decade ago, according to the state-run California Earthquake Authority. The premiums are higher and the coverage is less than before Northridge. The authority estimates that individual reimbursements for quake damage would be, on average, only about 43% of what they were from private insurers at the time of the Northridge quake.
As attention to earthquakes has faded, budgets have declined. The Seismic Safety Commission has reduced its staff by a third from the level of a decade ago. The state Conservation Department has not yet completed a project to map seismic hazards and identify where extra steps are needed to protect new buildings. And although the number of seismic monitoring stations in California has more than doubled, to about 850, some researchers say even more instruments are needed.
The trends worry people such as former Los Angeles Councilman Hal Bernson, who became the council’s leading seismic safety expert and championed the retrofitting of masonry buildings.
“We’re a little safer, but are we safe?” he asked. “No, we’re not. On a statewide basis, I don’t think we’re safe.”
If a Northridge-sized quake were to strike downtown Los Angeles, “it would do tremendous damage,” Bernson said. “Even with Northridge, had the shaking lasted 30 seconds longer, everything would have been destroyed.”
As it was, the Northridge quake killed 57 people and injured 4,500, causing about $40 billion in damage. Portions of the Santa Monica, Golden State and Ronald Reagan freeways collapsed. Los Angeles building inspectors recorded 113,000 structures as at least somewhat damaged.
Statewide, there have been some notable success stories in earthquake preparation since then. Tom Tobin, a former director of the Seismic Safety Commission, calls Berkeley “the gold standard” of retrofitting.
That city has a program that allows one-third of a 1.5% property transfer tax to be spent on retrofitting the dwelling being sold. Berkeley Assistant City Manager Arrietta Chakos said that, through fiscal 2003, the decade-old program had resulted in the retrofitting of 1,300 structures.
Hamburger pointed to several state university campuses that had embarked on slow but steady retrofit programs, including UC Berkeley, which straddles the dangerous Hayward fault.
That campus has about $1 billion in retrofitting to do, but even if that were completed, a catastrophic quake could still overwhelm the university, he said.
Tom Heaton, an earthquake engineering professor at Caltech widely regarded as a leading authority on California buildings’ quake readiness, said that despite consistently lower numbers of fatalities here compared with similar quakes in countries with poorer building codes, there is no reason to think major problems do not remain.
Even the Bay Area bridges being retrofitted or rebuilt would be question marks if a truly catastrophic quake were to strike, Heaton said. They should be able to cope with a quake the size of Northridge or Loma Prieta, which hit Northern California in 1989 -- magnitudes 6.7 and 7.1, respectively -- but it is not clear how they would fare in an 8.0.
A quake of that magnitude shaking over a wider area and for a longer time could be about 100 times more powerful than a 6.0 temblor.
Patrick Buscovich, an independent structural engineer in the Bay Area, said there is “a certain sense of denial” in California’s relationship with earthquakes.
“Loma Prieta created a perception that San Francisco had gone through a big earthquake, and that was the most we were going to have to cope with -- when it was moderate to minor, and quite distant from the city,” he said. “The earthquake gave people a really false sense of safety.”
The Northridge quake may have had the same effect. The quake measured 6.7 -- twice as powerful as last month’s temblor near San Simeon -- but it hit at 4:21 a.m. when roads were mostly empty. And 70% of the quake’s energy was expended north of the San Fernando Valley into the mountains.
Officials who deal with quake safety say that generating interest in the subject is a continuing battle against denial or complaints that upgrades are too costly.
Former Councilman Bernson recalled that he was successful in getting code upgrades for new, non-ductile concrete buildings and for so-called tilt-ups, “but I was unable to get retroactive features into the laws” mandating retrofitting.
Bernson also got an ordinance passed requiring new homes or homes improved at a cost of $10,000 or more to install gas shut-off valves.
But, he added, “homes that are not new or not sold don’t have to have the valves, so the fire danger in a quake remains considerable citywide.”
Denise King, spokeswoman for Southern California Gas & Electric, said the utility disputes the importance of the shut-off valves.
With most of these issues, much depends on how big an earthquake is. Since Los Angeles was founded in 1781, the basin has not had one larger in magnitude than Northridge.
Scientists have repeatedly said that a magnitude 7.5 quake was possible here. But predicting when and where a big one might hit is, for now, beyond their reach.
“We have so many faults -- over 300 of them capable of producing at least a magnitude 6.0 -- down here that there is a greater uncertainty on where the next quake will be,” said Lucy Jones, scientist in charge of the Pasadena office of the U.S. Geological Survey.
But one thing does seem certain. Each significant quake has its own surprising features and consequences.
“In Northridge, 200 steel-frame buildings had their welds cracked, and it wasn’t foreseen,” said Ross Stein, a U.S. Geological Survey scientist. “Northridge occurred on a fault unknown to us, and it produced phenomena, such as the damage in Sherman Oaks and Santa Monica, which had been unforeseen.
“These humbling experiences are a form of deja vu, and it makes us very cautious about making claims of being well-prepared,” Stein said. “In retrospect, so many elements of each earthquake have been a surprise. We have been too confident about our ability to fend off harm in the future.”