31 active fault zones in Japan may cause major quake within 30 years

Experts are warning that the likelihood of a major quake caused by 31 active fault zones in Japan is similar or greater than just before the Great Hanshin-Awaji Earthquake.

The quake hit the western prefecture of Hyogo and nearby regions on January 17, 1995. It was caused by the movement of inland active faults just below the affected areas.

The government has studied such active fault zones, each extending over 20 kilometers and likely to bring devastating damage if they cause a quake.

It has calculated and disclosed the likelihood of the fault zones causing a major quake within 30 years.

The likelihood of a major quake is classified on four levels. A zone of active faults judged to have a 3 percent or greater likelihood of causing a major quake is ranked at the highest level, labeled "S."

The 1995 quake is assessed to have had a likelihood from 0.02 through 8 percent just before it occurred, placing it at the "S" level.

As of January 1 this year, 31 of 114 major active fault zones were ranked at the same level.

Eight of them, including parts of the Itoigawa-Shizuoka-kozosen fault zone in central Japan, have a probability exceeding 8 percent.

This suggests that the likelihood of a major quake may be greater than before the 1995 disaster.

University of Tokyo Professor Emeritus Hirata Naoshi, who heads the government's Earthquake Research Committee, said the existence of active faults shows crucial evidence that major quakes have repeatedly occurred there.

He added that numerous such faults are located in inland and coastal Japan, and urged people to brace for a major quake.