Magazine article Science News

Quiet Hints Preceded Kobe Earthquake

Magazine article Science News

Quiet Hints Preceded Kobe Earthquake

Article excerpt

Months before last January's devastating earthquake, the ground beneath Kobe, Japan, started showing signs of an impending crisis. Subsurface water displayed chemical changes that intensified in the days before the disaster, two teams of Japanese scientists report in the July 7 Science.

The chemical hints came to light only after the Jan. 17 quake, so they could not help scientists predict the catastrophe, which killed more than 5,000 people. The findings are important, however, because they represent some of the best-documented cases of precursory phenomena--signals produced before a quake, says Urumu Tsunogai from the University of Tokyo.

Tsunogai and Hiroshi Wakita studied the concentration of dissolved chloride and sulfate ions in groundwater. The researchers had not collected water samples before the quake, so they took the innovative step of buying bottled water pumped from an aquifer near the quake's epicenter. Kobe's high-quality mineral waters are collected for drinking and for brewing sake, a rice wine. Because the bottles are stamped with a date, Tsunogai and Wakita could track chemical changes that occurred before and after the tremor.

From mid-1993 to mid-1994, concentrations of chloride and sulfate ions remained constant. Five months before the quake, the concentrations started climbing; they peaked in late February, after the jolt.

George Igarashi of Hiroshima University and his colleagues documented prequake changes in the concentration of dissolved radon gas measured at a monitoring site 30 kilometers from the tremor's epicenter. …

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