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| A team of local and foreign experts announces the results of its investigation of the cause of an earthquake that shook Pohang in November 2017, during a press conference in Seoul, Wednesday. /Yonhap |
By Bahk Eun-ji
An earthquake which struck the nation's southeastern city of Pohang, North Gyeongsang Province, in 2017, was triggered by an experimental geothermal power plant, the government said Wednesday.
The Geological Society of Korea-led research team, comprised of both local and international experts, concluded the construction of the nearby power plant played a role in the 5.4-magnitute earthquake that struck Nov. 15, 2017.
The earthquake, which was felt throughout South Gyeongsang Province and in the cities of Busan and Ulsan, was the nation's second-most-destructive tremor since observations began in 1978. The strongest occurred the previous year in Gyeongju, North Gyeongsang Province, measuring a magnitude 5.8.
In the wake of the strong earthquake, speculation was rampant that the plant may have caused it, and the government launched the investigation team in March last year to see if there was a correlation between the tremors and the facility.
The experts said the construction and test operations of the plant, involving pumping high-pressure water in and out of an underground reservoir, triggered the quake.
"The earthquake was an induced seismicity, not one that occurred naturally, because the geothermal plant aimed to generate power by boiling water beneath the earth's surface," said Lee Kang-gun, a natural science professor of Seoul National University who led the investigation.
Induced seismicity refers to tremors that are caused by human activity that changes the pressure on the Earth's crust.
Most conventional geothermal power plants draw heat directly from hot water deep underground, or pump fluid through hot rocks to exchange heat between the ground and the facility, which requires specific geological conditions.
Korea University geology professor Lee Jin-han and Pusan National University professor Kim Kwang-hee had previously raised the possibility of induced seismicity in a study published in the international academic journal Science Magazine last year.
However, some said the plant might not be the main cause of the earthquake, pointing out that the total amount of water injected into two holes on four occasions there was 12,000 thousand cubic meters, which was too little to trigger seismicity.
The investigation team, however, rejected the speculation that the Gyeongju earthquake affected the Pohang occurrence, saying the epicenters were far apart.
The quake left 118 people injured and damages cost 84.5 billion won ($75 million).
During the press conference, members of some civic groups staged a protest, demanding the government take responsibility and compensate people for their suffering.
