Features

San Francisco centennial

Disaster | Are Californians-and the rest of us-prepared for new disasters?

Issue: "Illegal passage," April 15, 2006

At the beginning of the 20th century, San Francisco was the financial hub of the West, the eighth-largest city in the country, and a cosmopolitan cultural center that on April 17, 1906, featured a rousing performance of Carmen with the great tenor Enrico Caruso.

At 5:12 the next morning, a major earthquake turned parts of the city into rubble-and what the quake didn't get a fire created by broken gas mains did. More than 30,000 people lost their lives in San Francisco alone; after three days of fires, 225,000 of the city's 400,000 citizens were homeless.

But that's past; many San Franciscans next week will be commemorating the centennial of their city's worst day while worrying that one even harsher is yet to come. It sounds like an urban legend, but there apparently was a FEMA emergency training session in August 2001 during which participants agreed on the three major disasters most likely to strike the United States: a New York terrorist attack, a massive hurricane hitting New Orleans, and a major California earthquake.

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Two of the three, of course, have occurred, and the third is likely: A U.S. Geological Survey working group in 2002 estimated a 62 percent probability of an earthquake measuring 6.7 or greater on the Richter scale in the San Francisco Bay area by 2032. University of California-Davis researchers in the Proceedings of the National Academy of Sciences late in 2005 gave the San Francisco area a 25 percent chance of being struck by a magnitude 7.0 or greater earthquake in the next 20 years, a 50 percent chance in the next 45 years, and a 75 percent chance in the next 80 years.

To interpret such figures, we need to know three things about earthquakes. The first is-no surprise-they are very powerful. A magnitude 5.0 yields as much energy as the Nagasaki atomic bomb. A magnitude 7.0 yields as much energy as the largest thermonuclear weapon ever made. The Pakistan earthquake in 2005 was a 7.6, the 1906 San Francisco earthquake is retrospectively estimated to have been anywhere from a 7.8 to an 8.25 (instruments were imprecise and the Richter scale itself wasn't devised until 1935), and the Indian Ocean earthquake that caused the terrible tsunami of 2004 was a 9.0.

The second is that, as with a bomb, the distance from its epicenter to major cities is crucial in determining the amount of damage. The California earthquake during the 1989 World Series was a 6.9. That would have been devastating had the epicenter been right under San Francisco, but it was 60 miles away. That earthquake killed 63 and created $10 billion of damage, but one with a similar Richter number that struck close to Kobe, Japan, six years later killed 6,500 people and caused at least $150 billion in damage.

Third, we need to understand the Richter scale, because the difference between a Richter 6.7 earthquake (probable in San Francisco by 2032) and a 7.0 (improbable) is far greater than it appears. The Richter scale is logarithmic, which means that the seismic waves of a magnitude 7.0 earthquake are 10 times greater than those of a 6.0, and the energy released (proportional to the square root of the cube of the amplitude) is 31 times greater. Or, to put it simply, a 7.0 is about 11 times more powerful than a 6.7.

This all means that the results of a "major earthquake" in northern California could vary from those resulting from a normal hurricane to those far worse than anything New Orleans saw. The common nightmare scenario has the equivalent of a massive nuclear weapon going off in the San Andreas Fault that runs beneath San Francisco. But another vision of horror has the epicenter of a 6.9-or-greater quake in Oakland or Berkeley; 1 million people live over the Hayward Fault, which runs right underneath the University of California football stadium.

The U.S. Geological Survey pegged the severe Hayward Fault possibility at only 8.5 percent during the next 30 years, so an East Bay politician playing Russian roulette with those odds is holding two six-shooters with a bullet in only one of the cylinders throughout the length of his career: Though "odds" do not restrict God's sovereignty, insurance agents and people generally use them to calculate probabilities (humanly speaking), and the odds of escaping disaster during a particular four-year term look good.

The same odds lead many to go without earthquake insurance. Premiums run $1,000 to $2,000 per year and only 15 percent of California homeowners carry it, with many apparently assuming that FEMA will bail them out if "the big one" does hit.

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