The No.1 plant is situated in Chinshan Township and the No.2 plant in Shihmen Township, on either side of a fault line running from the Guandu area in Taipei City’s Beitou District across the dormant Tatun Shan volcano to the coast.

The Central Geological Survey under the MOEA found the fault line had grown to 50 kilometers from an original length of 20 km and was likely to cause earthquakes of a magnitude up to seven, the Chinese-language Liberty Times reported Tuesday.

The No.1 nuclear plant was 7 km from the fault line, the No.2 only 5 km, the newspaper pointed out, adding that local government leaders had not been informed of the problem.

CGS President Lin Chao-tsung said last year’s research showed the fault line had extended inland. If it became active, it could provoke a 6.8-magnitude earthquake, Lin said, while underlining it was highly unlikely this would happen.

However, at the time, the No.1 plant was designed to withstand tremors of up to 7.3, and the No.2 could face down 8-magnitude quakes, said Hsu Huai-chiung, vice president of the Taiwan Power Corporation, the state-owned electricity company running the plants.

Taipower had requested experts from National Central University to conduct extra research into both plants’ structural safety, Hsu said. A geological evaluation of the nearby land and sea areas was under way to determine whether any strengthening needed to be done.

Academics and environmentalists said the discovery of the fault line’s true length was one more argument in favor of closing down the nuclear plants, especially the No.1, which has served for about 30 years. The government is considering the postponement of its original closure date of 2017 by 20 years.

Earthquakes frequently hit Taiwan, though the epicenters are often situated along the East Coast, near the counties of Ilan, Hualien and Taitung. The most devastating tremor of the past decades hit Central Taiwan’s Nantou County on September 21, 1999, killing more than 2,400 people islandwide.