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(LEAD) 2017 Pohang earthquake probably caused by geothermal plant

Science 15:03 March 20, 2019

(ATTN: CHANGES photo; ADDS more info throughout)

SEOUL, March 20 (Yonhap) -- South Korea's second-most destructive earthquake, which struck the southeastern city of Pohang in 2017, was probably triggered by an experimental geothermal power plant, the government said Wednesday.

The government-led teams of experts, from both South Korea and abroad, concluded that a series of earthquakes, reaching a magnitude of 5.4 on Nov. 15, 2017, could have been brought on by efforts to harness energy from the ground.

The study is the first official government finding that indicated the possible cause of the tremors that resulted in considerable damage in and around the industrial city, located 375 kilometers southeast of Seoul.

Fluids are injected at high pressure into a hole about four and five kilometers deep at the geothermal power plant, which may cause the surrounding rock to crack, the scientists said. During the process, seismic activity can occur, which could cause earthquakes.

"A series of micro-sized earthquakes occurred when fluids were injected by excavating a geothermal well at the geothermal power plant, which eventually triggered the Pohang earthquake," Lee Kang-keun said

The government-led team was offered two separate assessments though both found the plant ability to trigger a tremor as being plausible.

"We use the word, trigger, as the earthquake occurred beyond the scope of stimulated area," Lee said. "It was not a natural earthquake."

The Pohang quake was the most disruptive to hit the country since observations began in 1978. The temblor left dozens of people injured and more than 2,000 homes damaged.

The strongest quake, which occurred in September 2016, reached a magnitude of 5.8 and had its epicenter near a township south of Gyeongju, 370 kilometers south of Seoul.

A team of local and foreign experts announces the results of its study on the cause of the Pohang earthquake at a press conference in Seoul on March 20, 2019. The team concluded that a geothermal power plant likely triggered the November 2017 quake in the city of Pohang, 375 kilometers southeast of Seoul, as it harnessed energy from the ground. Civic groups staged protests at the press conference, demanding that the government take responsibility and compensate people for their suffering. (Yonhap)


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