Earthquake Preparedness: Lessons from San Francisco

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Dave Bartruff / Corbis

Repair crews in Oakland, Calif., examine damage to the Cypress Structure during the 1989 San Francisco earthquake

The San Francisco Giants and the Oakland Athletics were just about to start Game 3 of the 1989 World Series on Oct. 17 when the shaking began. ABC play-by-play announcer Al Michaels managed to tell viewers, "We're having an earth—" before the signal went dead. The temblor was brief — just 15 seconds — but the damage caused by the 6.9-magnitude quake was impressive. It killed 63 people, injured thousands and caused $7 billion worth of damage throughout California's Bay Area, including major destruction to the Oakland Bay Bridge. "It was a good sized shock," says Peter Yanev, chairman of Risk Solutions International and the author of Peace of Mind in Earthquake Country.

Looking back 20 years later, however, seismologists say the Bay Area got lucky. The epicenter of the quake was near Loma Prieta peak in Santa Clara County, outside the densely populated urban neighborhoods of San Francisco and Oakland. The destruction missed Silicon Valley — with its tens of billions in economic value — altogether. "If that quake had to happen, that was really the best place," says Yanev. "We were about as lucky as we could get."

Chances are we won't get that lucky again in earthquake-prone San Francisco or in any of the cities around the world that sit on unstable land. According to a 2008 study by the U.S. Geological Survey (USGS), there's a more than 99% chance that a quake of magnitude 6.7 or higher will hit California over the next 30 years and a nearly 50% chance that a magnitude 7.5 or higher quake will hit the state over the same period. Tokyo, Tehran, Istanbul, Seattle, St. Louis — all are major cities built on land that has experienced massive quakes in the past and almost certainly will in the future.

The difference between then and now is that these cities are growing, which means more and more people will be living in seismological danger zones. The key to minimizing damage is to prepare for the inevitable. "The Loma Prieta quake was really a wake-up call for this region," says David Schwartz, a USGS geologist and the co-chair of the San Francisco Bay Area Earthquake Alliance. "But we still have a lot to do."

California's responses to the 1989 quake and to a 1994 temblor in Los Angeles are instructive. First, there's the science of quake analysis and prediction. In 1989 the Bay Area had only 75 accelerometer sensors, which locate quakes and determine their intensity. Today, there are more than 200, which allow seismologists to more immediately pin down the size and strength of an earthquake as it happens. Many of those sensors have also been equipped with global-positioning system add-ons, which can determine the rate at which a quake has caused a fault to slip. Scientists in the Bay Area have also dug several deep trenches that expose rock layers that have been deformed by quakes — that helps give them a better sense of how often earthquakes hit and when the next one may come. Scientists still can't predict earthquakes the way they might predict a hurricane, but thanks to this richer data, they are getting a little closer. "We are getting better at understanding the probabilities of earthquakes," says Lucy Jones, chief scientist of the USGS's Earthquake Hazards Program.

Since earthquakes can't be accurately predicted or stopped, the key to preventing damage is to prepare. The death toll and destruction from a serious temblor often has less to do with the strength of the quake than with the strength of building codes and emergency-response plans. In the years since the 1989 quake, California has reinforced building codes, especially for public structures like schools and hospitals, while the state government has spent billions to improve the reliability of highways, bridges and roads. The Bay Bridge — which partly collapsed in 1989 — is being remade to handle the largest plausible earthquake expected to occur over a 1,500-year period. "We're in much better shape for emergency response," says Jones.

But even in California, older private homes remain a challenge. Although new structures are built in compliance with toughened building codes, existing homes need to be retrofitted to get up to code — but that can be costly, and right now there's little in the way of aid for homeowners who might want to quakeproof their homes. That means there are still countless older structures that aren't built to resist earthquakes — especially strong ones — and could collapse during a major temblor, which is exactly how most of the deaths in the 1989 quake occurred. "If you have a 20-story apartment building built in 1920, that structure is a collapse hazard," says Yanev. "We know the problem, but the political will is not there to fix it."

Cities like Seattle and St. Louis — which lie in seismological danger zones but where quakes haven't occurred for centuries — are even less prepared. And the worst disasters will continue to occur in the cities of the developing world, in places like Tehran and Gujarat, India, where sheer population density and virtually nonexistent building codes can lead to death tolls in the tens of thousands during a strong quake. That was clear during the May 2008 earthquake in western China, when some 20,000 children and teachers were killed in the collapse of shoddily constructed schools. "What happened in China happens too often," says Yanev. "They think it can't happen here, until it does, and they're not prepared." Twenty years later, the lessons of 1989 are clear — we just have to heed them.