‘94 Northridge Quake Still Teaching Lessons

Two years after the Northridge earthquake, the event is fading into history. But its lasting significance is coming into sharper focus.

Northridge and the more calamitous Kobe earthquake, which followed a year to the day later, have become twin landmarks in shaping critical perceptions of disasters in both America and Japan.

Together, they have helped define natural catastrophe. They forced government and business--especially the insurance industry--to come to grips with the magnitude of future losses, and to consider new ways to protect property while limiting financial exposure.

They gave scientists and engineers greater appreciation of the need for more precise measurement and understanding of the mechanics of heavy shaking and its effects on buildings, bridges and lifelines.

To residents of both urban areas, they brought the terrors of shaking, fires, homelessness, injury and death. Even to outsiders not directly involved, the images were searing.

As the recovery speeds forward--city officials have already declared victory in the war on “ghost towns,” city schools earlier this month received virtually all of the federal assistance requested, and the number of permits issued for quake repairs continues to rise--some still look back.

The great lesson of Northridge is “the realization that a moderate size earthquake could do so much damage,” said Richard McCarthy, acting director of the state Seismic Safety Commission. “That was a surprise to a lot of people.”

At magnitude 6.7, Northridge was not as strong as three other quakes occurring in California since 1989--Loma Prieta, Humboldt County and Landers.

It was the most devastating, however, because its epicenter was in a metropolis. The 681,710 applicants for government assistance following the quake were more than twice the number of any other disaster in U.S. history, according to the state Office of Emergency Services.

Yet Kobe was far worse--about 5,400 deaths, compared to a recently updated 72 for Northridge, and, at more than $100 billion in damage, just over four times more than the most recent official $25-billion damage estimate for Northridge.

At magnitude 6.9, Kobe was about twice as powerful an earthquake as Northridge, but the main reason for its greater devastation was that its strongest shaking was more focused in a heavily populated area--downtown Kobe.

Despite the unprecedented levels of destruction, about 60% of the energy of the Northridge temblor was dissipated in the Santa Susana Mountains and other areas where there weren’t many people, scientists have now confirmed.

It occurred on a south-dipping thrust fault that did not intersect the surface, a fault that has still not clearly been identified. So even if the epicenter was in the center of the San Fernando Valley, the thrust of most of the quake’s energy was to the north, out of the Valley.

“Had this been a (south thrusting) fault instead, the Valley and all of Los Angeles would have suffered much more,” said Caltech seismologist Egill Hauksson It still was a destructive earthquake. Insured loss alone was $12.5 billion, $8.2 billion residential and $4.3 billion commercial. Federal government assistance, according to the White House Office of Management and Budget, also exceeds $12 billion.

Fred Messick, a spokesman for the state OES, said last week the latest figures show 114,039 buildings were damaged in the quake.

Through Dec. 31, 1995, a total of 12,548 aftershocks over magnitude 1.5 had been recorded. Of these, 10 registered magnitude 5 or greater, 48 were between magnitudes 4.0 and 4.9 and 382 were between magnitudes 3.0 and 3.9.

Aftershocks continue. On Friday and Saturday there were three such tremors reported with magnitudes of 3.5, 3.0, and 2.8. No damage was reported.

Besides the deaths, 11,846 people were treated for quake-related injuries in hospitals in Los Angeles, Ventura and Orange counties, according to Michael E. Durkin, a Woodland Hills researcher.

The great surprise of the Northridge quake was which buildings fared well and which did not.

The heavy damage to steel-frame buildings, and evidence that other failures were due to poor design and workmanship, were among the worst surprises, according to the Seismic Safety Commission’s McCarthy.

Thomas Heaton, Caltech professor of engineering seismology, added the collapse of several parking garages, especially of the precast variety, and the general economic losses leading to high insurance claims.

Maryann T. Phipps, president of the Structural Engineers Assn. of California, added the failure of many buildings with so-called “soft stories,” such as parking garages underneath apartments; the collapse of “tilt-ups,” where concrete panels are poured on the spot and then tilted up to become walls; and the importance of “near-source effects,” intense shaking of areas closest to faults.

Phipps said the retrofit of existing buildings is a future necessity.

“Northridge did not confirm that everything is fine,” Heaton said. “Deaths were held down, but still we saw lots of areas that need a lot of work, and we were lucky that Northridge didn’t send its worst waves into Downtown Los Angeles.”

Since Northridge, the Structural Engineers Assn. has submitted recommendations for a comprehensive revision of building codes to the International Conference of Building Officials, and if approved, it will be published in the 1997 Uniform Building Code.

Engineers have yet to agree on the best way to retrofit multistory steel-frame buildings, leaving owners and regulators in limbo. In some cases, existing code worked, in others--most notably parking garages--it did not.

“Largely, we found the soft stories didn’t meet the current code,” Phipps said. “The code was OK, it was the application of the code that was deficient. . . . It was a bad design that was to blame for the collapses.”

Research is also underway to determine uniform standards for retrofitting private homes and small businesses. When complete, Phipps said, “We will be better able as engineers to deal with the issues raised by Northridge and Kobe. We will have better techniques.

“But there also must be incentives for owners to use those techniques. That’s a huge political question.”

City officials have prepared a retrofitting program that could cover as many as 80,000 residential and commercial buildings over the next 10 years. But the city has yet to determine whether retrofitting will be mandatory or voluntary.

The costs of retrofitting are shown in programs to strengthen state highway bridges. In the first phase, almost 90% of the work has been completed at a cost of $763 million due to the Loma Prieta quake seven years ago. But as a result of the Northridge quake, only 59 of 1,179 bridges have been completed in a second phase. The overall cost is estimated at more than $1 billion.

Jim Drago, chief spokesman for Caltrans, said that in addition, 252 local bridges in Los Angeles County need retrofitting. Only nine have been completed and eight are under construction.

On the whole effort to prepare for the next big earthquake, leading seismic authority L. Thomas Tobin, former director of the state Seismic Safety Commission, expressed concern.

“There’s room for lots of value judgments as to how fast progress will be,” he said in an interview. “But there’s a question whether we’ve lost momentum. There have been some fits and starts and miscommunications.”

But Joanne Kozberg, secretary of the State and Consumer Services agency and chair of the state Building Standards Commission, said action is coming.

Noting that in December, Gov. Pete Wilson named Harry C. Hallenbeck, California’s state architect, to the new post of state director of Seismic Safety Implementation, Kozberg said she sees him as “an ombudsman to insure that the momentum continues.”

To be sure, recovery is not yet complete. In every neighborhood, quake-related events continue. Just last week, at the corner of Woodman Avenue and Albers Street in Van Nuys, a damaged house was demolished and the ground prepared for a new one.

On Moorpark Street in Sherman Oaks, Steven Jasa, vice president of a real estate leasing firm, spoke enthusiastically about the pace of reoccupying an 80-unit apartment house reopened last month.

“The market itself is better,” he said. “A year ago, it was tough to get good rents. Now, we’ve rented half these units in 30 days at $925 to $1,295 a month, better than we could have gotten before the quake.”

Meanwhile, the state is moving toward creation of an earthquake authority, with industry participation, to ensure that at least some, although more limited, coverage will be available in the future.

For the time being, seismic activity in California seems less. There have not been any quakes in the state over magnitude 5.8 in the last 16 months.

But, experts are unanimous, there will be other big quakes, and California should be getting ready.