Japan's capital has a 90 percent chance of being devastated by a major earthquake some time in the next 50 years, according to a study by a government panel.
The study, released earlier this week, marked the latest attempt by scientists to address one of this quake-prone country's most pressing concerns: when the next "Big One" would level one of the world's most densely populated cities.
Tokyo was last hit by a destructive quake in 1923 that toppled buildings, set the city aflame and killed at least 140,000 people, and experts warn it's overdue for another.
Norihito Umino, a Tohoku University seismologist on the 12-member Earthquake Research Committee, said researchers thought a statistical approach would take some of the guesswork out of predicting the next huge quake.
"We wanted to quantify quake prediction," he told The Associated Press.
They found that as time goes by, the risk of a major magnitude-7 temblor increases: In the next decade, there's only a 30 percent chance; over 30 years, it's 70 percent. The probability rises to 90 percent over 50 years.
Forecasting quakes is generally considered to be impossible with current technology. But that hasn't stopped seismologists from trying.
Japan's Meteorological Agency began testing an experimental early warning system earlier this year that detects tiny shock waves moments before people would feel the ground shake. Last year, two unconventional studies suggested that erratic behavior in dogs and abnormal VHF radiowave fluctuations might indicate an imminent quake.
Umino said researchers pored over data analyzing the five major quakes with magnitude of 6.7 to 7.2 near Tokyo since 1885. Those were big enough to bring down buildings and wreak havoc, and are believed to have been caused by a shifting of three tectonic plates, or slabs covering the earth, on which Japan sits.
He said the committee's analysis showed that the chance of a magnitude-8 earthquake, similar in power to the magnitude-8.3 quake of 1923, was zero to 0.8 percent over the next three decades.
The Earthquake Research Committee, formed after a Jan. 17, 1995 quake killed more than 6,000 people in Kobe, studied all of Japan's 98 active faults lines. They will finish their work by the end of March 2005.
Japan is rattled by hundreds of quakes a year because it is situated atop four tectonic plates. Powerful quakes in 1703, 1782, 1812 and 1855 caused vast damage in Tokyo.