Still Shaking Things Up : 2 Years Later, Northridge Quake Continues to Teach Lessons on Disaster

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 a year to the day later, Jan. 17, have become twin landmarks in shaping critical perceptions of disasters in both America and Japan.

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, 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.

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

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

Yet Kobe was far worse--about 5,400 deaths, contrasted with a recently updated 72 for Northridge, and more than $100 billion in damage, just over four times the most recent $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 casualty toll and devastation was that its strongest shaking was more focused in a heavily populated area--downtown Kobe--than Northridge.

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 heart 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 very 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 the latest figures show 114,039 buildings were damaged.

Through Dec. 31, 1995, 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 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 Seismic Safety Commission’s McCarthy.

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

Maryann T. Phipps, president of 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,” very intense shaking of areas that are closest to faults.

Phipps said the retrofit of existing buildings such as private homes is a necessity.

“Clearly, we are grappling with some fairly fundamental questions as to what happens in large earthquakes and how well we understand performance of all our structures,” Heaton said.

“Northridge did not confirm that everything is fine,” he 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. 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.

“The code was OK, it was the application of the code that was deficient,” Phipps said. “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,” Phipps said. “That’s a huge political question.”

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

The costs are shown in programs to strengthen state highway bridges. In the first phase, due to the Loma Prieta quake 7 years ago, almost 90% of the work has been completed at a cost of $763 million. But in a second phase, as a result of the Northridge quake, only 59 of 1,179 bridges have been completed. The overall cost is estimated at over $1 billion.

Jim Drago, chief spokesman for Caltrans, said an additional 252 local bridges in Los Angeles County need retrofitting. Only nine have been completed, eight are under construction, and the rest are in the planning stages.

Just last month, the costs of retrofitting the Golden Gate Bridge alone--one of nine toll bridges that require retrofitting--was put at $175 million.

On the overall effort to prepare for the next big earthquake, a 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. “But there’s a question whether we’ve lost momentum. There have been some fits and starts and miscommunications.”

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

Last month, she noted, Gov. Pete Wilson named Harry C. Hallenbeck, California’s state architect, to the new post of state director of Seismic Safety Implementation. Kozberg sees him as “an ombudsman to ensure that the momentum continues.”

The process of adopting new building codes “is a long one,” Kozberg said. “But we’ve got to put California’s agenda forward to influence the rest of the country. . . . There are 39 states that should be concerned with earthquakes.”

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.

A short distance away, on Moorpark Street in Sherman Oaks, a particularly hard-hit area, Steven Jasa, vice president of a real estate leasing firm, spoke enthusiastically about the pace of renting out an 80-unit apartment house reopened last month.

“The market itself is better,” he said. “It’s hardening up. It’s coming around. 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.”

Although a few homeowners have yet to resolve disputes with insurance companies over how much they will receive for damage, the state is moving toward creation of an earthquake authority, with industry participation, to ensure that at least some--though more limited--coverage will be available in the future.

Meanwhile, there have not been any quakes in the state over magnitude 5.8 in the last 16 months.

But, experts are unanimous on one point: There will be other big quakes in the future, and California should be getting ready.

(BEGIN TEXT OF INFOBOX / INFOGRAPHIC)

A Lesser Disaster

A recent study has shown that the most intense shaking during the Northridge earthquake occurred in relatively unpopulated areas.

Deadly Energy

Kobe (6.9)

The energy released by the 1995 Kobe earthquake was primarily focused in the thickly populated downtown area, accounting for most of the 5,400 deaths.

*

Northridge (6.7)

The energy released by the 1994 Northridge earthquake moved upward and to the north of the epicenter.

* Source: California Office of Emergency Services