Within days of the news reports, the university’s Earthquake Research Institute posted a lengthy disclaimer on its Web site, saying the forecast was just the opinion of two of its researchers and noting that the study had a “large margin of error.” Colleagues said the report jumped to conclusions that other earthquake experts didn’t support.
“Many seismologists think this kind of study is too simple,” said Naoyuki Kato, a seismologist at the institute.
The growing skepticism here about earthquake forecasts is the byproduct of Japan’s long, expensive and fruitless effort to figure out where and when the big ones will strike. Last year’s March 11 mega-earthquake, unforeseen by experts, only reinforced those scientific shortcomings: All of Japan is vulnerable to huge quakes, some experts say, but that’s about all we know for sure.
The skepticism is shared by seismologists worldwide, but Japan is the world’s earthquake capital, and no country spends more on forecasting temblors.
A search for clues
For decades, researchers in this island nation have studied historical data, dug through fault lines, attached instruments to the sea floor and pulverized rocks in laboratories — all in a search for clues about how the earth behaves before it slips, shifts and shakes.
Unlock that mystery, scientists say, and they could make predictions (“Tokyo will have a 7.0 quake tomorrow”) with enough warning time to allow a city to be evacuated. They could also make broad and accurate forecasts (“There’s a 70 percent chance Tokyo will have a 7.0 quake within the next four years”) that could influence everything from building codes to government planning.
Experts have spent decades looking for earthquake precursors by examining changes in the levels of water and radon gas, electrical current and animal behavior. They have frequently had their hopes raised. In the laboratory, for instance, rocks under pressure show small signs of rupture before a dramatic slip, suggesting the possibility that “pre-slip” deformations could signal a developing earthquake. But most scientists say that pre-slip movement, if it exists in real life, is too inconspicuous to serve as a clue.
There’s also the common but fraught practice of forecasting earthquakes by using apparent historical patterns. In some regions of the country, major quakes usually happen every 100 or 150 years. But even those areas can remain calm for three centuries.
In Tokyo, which had its last major quake in 1923, centuries of records produce no clear pattern. Sometimes, most notably with last year’s 9.0 magnitude temblor, the problem is history itself: Scientists either lack enough data to see the pattern, or they don’t see one until it’s too late.