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Earthquake experts got it right about Nepal. What about Japan, California and Mexico? [Updated]

imrsDamaged buildings lean to their sides in Kathmandu, Nepal, on April 27. A magnitude 7.8 earthquake shook Nepal’s capital and the densely populated Kathmandu Valley on April 25, causing extensive damage, with toppled walls and collapsed buildings. (Wally Santana/AP)

Writing about seismic risk is frustrating: The experts know that big earthquakes are going to happen, but not exactly when and where. The ensuing articles are laced with hypotheticals. There is an airy, foamy quality to these stories; as a writer, you long for solid facts and certainties, and wonder whether any of this stuff makes a difference on the ground, in lives of actual human beings who are at risk. For example, here’s a story I wrote five years ago:

The next Big One could strike Tokyo, Istanbul, Tehran, Mexico City, New Delhi, Kathmandu or the two metropolises near California’s San Andreas Fault, Los Angeles and San Francisco. Or it could devastate Dhaka, Jakarta, Karachi, Manila, Cairo, Osaka, Lima or Bogota. The list goes on and on …

For years, earthquake scientists have shouted their warnings about the strong likelihood that a major quake would level an impoverished city and kill hundreds of thousands of people. They have said, for example, that Kathmandu, where masonry structures expand so haphazardly that some eventually cantilever over narrow city streets, is every bit as vulnerable as the surrounding Himalayas are majestic.

For years, scientists have talked to me about the very high likelihood of a Kathmandu earthquake. It happened Saturday. The experts called it. But being right hasn’t made them any less horrified and saddened by this disaster. In fact, they sounded dismayed, as if overcome with a sense of powerlessness. Tectonic forces are massive and implacable, and human societies are often poor and fragile.

India is crashing into Eurasia; the result is the Himalaya Mountains. People live in valleys where the softer sediments amplify shaking; see Kathmandu. Urbanization is a long-term global trend that has accelerated in Nepal due to political unrest in the countryside. You can talk all day long about how it is dangerous to live and work and pray in certain kinds of masonry structures or in buildings with a “soft” first floor, but in poor countries people are just trying to get by day to day. They have no choice but to play the lottery when it comes to a hypothetical natural disaster that might come along once or twice a century.

I talked about this on Science Friday a few years ago:

If you go back to 1800, the year 1800, there was one city in the world that had a million people, and that was Beijing. The most recent count I’ve come across is that there are 381 cities with at least a million people. Of those cities, a lot of them are in seismically very hazardous places like Caracas, Venezuela, or Mexico City or Katmandu.

And if you’re living in a city, and you are poor, you’re not going to worry about events that don’t happen but once every 200 years or so.

Earthquakes are innately unpredictable, and don’t let anyone tell you otherwise. Skittish birds and snakes are not a reliable indicator. No one knows why a small earthquake can keep breaking and turn into a 1906-style catastrophic rupture. Sometimes they stop, sometimes they keep going. The 2011 Japan earthquake was a 9.0 on a fault that, according to the scientific consensus, could generate only magnitude 7 and 8 earthquakes. On a logarithmic scale, a 9 is 10 times more powerful than an 8 and 100 times more powerful than a 7. (One Japanese scientist did manage to figure out, a few years before the earthquake, that a 9 was possible; being correct did not make him feel any better when the horrible news came.)

Japan, to its credit, has prepared for earthquakes, and retains cultural memory of the 1923 earthquake and fire that devastated Tokyo. But what happened in 2011 defied the received wisdom in Japan about where the next big one would be. Here’s a brief excerpt of my 2006 story in National Geographic on earthquake prediction:

In Japan, government scientists say they have settled the question. Earthquakes are not random. They follow a pattern. They have detectable precursors. The government knows where Japan’s big one will most likely strike. This is a country where the trains run on time, and earthquakes are supposed to do the same. “We believe that earthquake prediction is possible,” says Koshun Yamaoka, a scientist at the Earthquake Research Institute of the University of Tokyo.

Japan has already named its next great earthquake: the Tokai earthquake. The government has identified and delineated by law the precise affected area — a region along the Pacific coast about a hundred miles (160 kilometers) southwest of Tokyo. After a series of small quakes in the Tokai area in the 1970s, scientists predicted that a major quake might be imminent there. The Japanese government passed a law in 1978 mandating that preparations begin for the Tokai earthquake.

Scientists have estimated a death toll of between 7,900 and 9,200 for a quake striking without warning in the wee hours. Estimated property damage: up to 310 billion dollars. At the Tokai earthquake preparedness center in Shizuoka, a map pinpoints 6,449 landslide locations. Another map shows where 58,402 houses could burn in quake-related fires. It’s all remarkably enumerated. The only thing left is for the earthquake to happen.

It hasn’t happened. The Big One turned out to be hundreds of miles to the north.

Here’s a prediction: There will be a huge earthquake in California. The San Andreas Fault will rupture and produce something close to a magnitude 8.0. If you had to bet, you’d wager it would be in the southernmost section, which hasn’t ruptured since about 1680. But who knows?


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