When two University of Tokyo seismologists recently released a study forecasting that a major earthquake would strike the capital and its 13 million inhabitants sometime in the next four years, they made front-page headlines.
But their forecast also came with a backlash, as other researchers studying earthquakes bristled at the forecast, saying such predictions shouldn’t be attempted in the first place because they’re more likely wrong than right, at least based on Japan’s history.
Within days of the attention-grabbing headlines, the University of Tokyo’s Earthquake Research Institute — where they both work — placed a lengthy disclaimer on its website.
“Many seismologists think this kind of study is too simple,” said Naoyuki Kato, a seismologist and fellow colleague at the institute.
The growing skepticism about earthquake forecasts is a byproduct of Japan’s long, expensive and fruitless effort to predict where and when the big ones will strike.
Seismologists’ failure to forecast the 9.0-magnitude temblor that struck off Tohoku on March 11 only reinforced the science’s shortcomings: All of Japan is vulnerable to huge quakes, some experts now say, but that’s about all we know for sure. Such skepticism is shared by seismologists worldwide, but Japan is the world’s earthquake capital and no country spends more money on attempts to forecast earthquakes.
For decades now, researchers have studied historical data, dug through fault lines, attached instruments to the seafloor and pulverized rocks in laboratories to search for clues about how the Earth behaves before a big quake.
Unlock that mystery, scientists say, and they could make predictions such as: “Tokyo will have a 7.0-magnitude quake tomorrow” with enough warning time to safely evacuate entire cities. They could even make accurate broad forecasts — “There’s a 70 percent chance Tokyo will have a 7.0-magnitude quake within the next four years” — that could influence everything from building codes to government planning.
There’s also the common but fraught practice of forecasting earthquakes by using apparent historical patterns. In some regions of the country, major quakes happen every 100 or 150 years. But even in the most vulnerable places sometimes go 300 years without a huge temblor.
Sometimes, most notably with the March 11 megaquake, the problem is history itself: Scientists lack the data to go far back enough to identify a pattern. Or they don’t see one until it’s too late.
According to the government-issued earthquake hazard map, the northeastern coast was among the least likely places in the country to experience a major jolt.
As it turned out, the northeastern coast was indeed susceptible to major quakes. But the region hadn’t seen one since the year 869, and only after the March 11 temblor were there enough data to even guess at a cycle.
“Over 400 years up (in Tohoku), there were maybe a dozen magnitude 7.0 quakes. People thought they understood that,” said Jim Mori, an earthquake researcher at Kyoto University. “But it turned out, you couldn’t see the pattern over 400 or 500 years. You had to go back 1,000 years to see a pattern.”