Earthquake Report: Learning the Hard Way
By Andrea Perkins
Earthquakes don't kill people, buildings do.
Buildings are intricate and complex agglomerations of bolts, beams, planks, nails, glass panes, wood, steel and sheet rock, all of which become potentially lethal objects during an earthquake.
"We still don't understand everything about how buildings react during earthquakes," says Jim Russell, building code consultant for the San Francisco Bay Area. "We learn more after every major disaster."
We learn the hard way.
Fifty-seven dead at Northridge.
Sixty-three dead at Loma Prieta and 13,757 injured, in less than 15 seconds of ground shaking. Loma Prieta was a moderate earthquake, and its epicenter was located more than 50 miles south of crowded San Francisco.
The quake in Kobe, Japan, six years later showed us what could happen when a big one rips through San Francisco proper. Kobe's large strike-slip faults, located near a bay, and its buildings, constructed on sedimentary deposits and landfill, approximate the San Francisco situation. In Kobe, 5,400 died. Injuries were in the tens of thousands. Estimated damage reached over $150 billion. Yet the quake was relatively moderate, registering a magnitude of only 6.9.
A major earthquake, like last year's in northwest Turkey, which measured 7.4 and killed an estimated 40,000 people, would probably devastate the Bay Area. In Turkey, 54,295 buildings suffered damage, suddenly leaving more than one million people homeless.
A recent U.S. Geological Survey found that there is an 80 percent chance that one or more quakes of a magnitude of at least 6 will wreak havoc upon the Bay Area before 2030. There is a 70 percent chance of an even bigger quake, of a magnitude of at least 6.7.
Everybody knows this. Every Bay Area resident knows that earthquakes are eventualities, not just possibilities. And yet, how prepared is this precariously built city for the disaster that will eventually strike?
"Older buildings and apartments are definitely underprepared," says Russell. He's a bona fide seismic safety expert, formerly Chief Building Official for Walnut Creek and the author of two important California building codes that specifically address buildings constructed before modern safety standards were established. He's also the person sent out to inspect buildings in the aftermath of a quake.
"We expect some older buildings to be damaged, because they were never built with earthquakes in mind," he says. "Many, many newer buildings constructed after the adoption of modern codes," he says, "suffer unacceptable levels of damage as well."
This he attributes not to the code itself, but to its enforcement. To obtain a building permit, applicants must submit drawings that comply with code. However, when construction begins, the statutory requirements are sometimes ignored in order to cut costs.
Russell doesn't put all the blame on the machinations of capitalism or the carelessness of construction companies. "Building departments need more funding in order to hire all the qualified people required to do really adequate inspections," he says.
They also need more funding to gather the information needed to institute more effective mitigation measures. This is a surprisingly slow process, given what we know about what happens in a quake. It has only been in the last couple of years, for example, that the city has accurately mapped liquefiable soil areas, such as those comprised of old landfill or saturated sand. These delicate areas are especially vulnerable during earthquakes. They are often densely developed, like Multimedia Gulch, which is located on the worst fill in the city. Only now is the city conducting a "hazardous building survey," the very first citywide, comprehensive look at the potential social and economical consequences of a major earthquake, and an attempt to identify which types of building pose the greatest threat. The results are not yet in.
It seems surprising in a city that lived through the great quake of 1906 that such action hasn't been taken long before now. One might attribute this to a pervasive sense of denial. The few codes that were in existence in '06 were actually relaxed afterward to encourage rebuilding. Furthermore, many authorities claimed (perhaps to palliate the insurance companies) that the real destruction was the result of the fires, not the earthquake. Denial, undoubtedly. This has left a legacy of highly unfit structures looming all around us. Fortunately, steps are being taken to strengthen them.
"We're now able to do more to prepare for an earthquake, due to several important factors," says Lawrence Kornfield, chief building inspector. "We've come leaps and bounds in the fields of earthquake engineering and risk assessment. It also helps that insurance companies are becoming more willing to focus on probable loss."
Yet the process of earthquake preparedness remains complicated. Unfortunately, money is often the deciding factor at all levels. Different buildings require different treatment. The provisions for wood-frame houses, for example, are different from those for concrete tilt-up buildings, such as the ones that cover Silicon Valley, but their location must also be taken into consideration. This is where things can get tricky, because it's impossible to predict the spot where an earthquake will hit or its level of ground motion. Even in long-established earthquake country, like California, quakes can occur in places that are believed to be safe -- Northridge, for example. The 1994 quake, the costliest in U.S. history, leaving over $20 billion in property damage, occurred along a previously unknown fault line.
As a result of Northridge, the state implemented city programs to retrofit unreinforced masonry buildings, the ones most at risk. Generally defined as "structures without steel reinforcing within a masonry wall" (definitions differ from city to city), these were the only structures built before 1933. Though they clutter significant portions of San Francisco, they account for only 5.8 percent of all housing in the county. The most common form of shelter in the city are the three-story wood-frame buildings constructed before 1940, quaint examples of quintessential West Coast architecture that may suffer serious foundation damage in a major earthquake.
"Building and homeowners don't always have the capital to retrofit, which can be an extremely costly procedure," explains Russell. Only one governmental loan program has attempted to offer substantially reduced earthquake insurance for those who retrofit, and few commercial building owners have taken advantage of it.
Homeowners are equally reticent. A recent survey conducted by the Association of Bay Area Governments shows that only 10-15 percent of all single-family homeowners are prepared for a seismic catastrophe. Similar surveys show apartment owners are no better outfitted.
Nobody is saying whether or not they know just how many buildings have been retrofitted, but the educated guess is that the number is also chillingly low.
"The government can't force people to strengthen their buildings. The only thing we can do is offer them incentives," says Russell.
One such incentive is an Assembly bill being introduced by assembly members Ellen Corbett and John Scott. Bill #AB1756 offers tax credits to owners of single- and multi-family structures who retrofit. Jim Russell, who has been an advocate of the bill for 10 years, hopes that this will finally allow many home and apartment owners to take the necessary measures to protect themselves and others. "This is the most important thing that's ever come up to encourage people to take action," he says.
Though state and city programs to promote retrofitting have, until now, been minimal, even fewer attempts have been made to address other public safety issues. The current California Building Code has earthquake provisions that mainly concern ground motion, while neglecting other effects of quakes, such as landsliding, liquefaction and hazardous material spills that can also damage buildings and endanger lives.
Further technological advances will undoubtedly increase our awareness of earthquake preparedness. And more funding will enable more studies to be done, which in turn will lead to building codes and public safety laws. Jim Russell is currently managing one such study, the "wood house project," funded by a grant of $6 million from the Federal Emergency Mitigation Association.
"We're building multilevel wood houses and testing them on giant shake tables," he explains with the enthusiasm of a young boy talking about his new train set. "This kind of thing has never before been done in the United States. We're gathering experimental data to validate what's in our codes, because up until now, we haven't really been able to do that. We're looking at every nail and how it twists and turns during an earthquake, so we can come up with better solutions."
For additional CoastNews.com earthquake stories see: