Correlation on geothermal work with recent earthquake being investigated in South Korea

Drilling rig on project site in Pohang/ South Korea (source: DESTRESS Project)
Alexander Richter 4 Dec 2017

Following an earthquake in Pohang, South Korea, geologists and scientists are now exploring any possible correlation with a geothermal project nearby the epicenter of the event.

Several news posts and a report by the DESTRESS geothermal research project team report that on 15 November 2017 at 05.29 UTC (14.29 local time) an earthquake with a magnitude of 5.4 occurred near Pohang in South Korea took place. “This earthquake is the second-largest on record in Korea after the magnitude 5.8 Gyeongju event, which occurred in 2016, 40 km from Pohang. It triggered numerous aftershocks in the following months.

There may be concerns regarding a connection between the recent earthquake and the nearby Pohang geothermal project due to the close proximity and shallow depth of the earthquake. Analysis is underway regarding the injection activities in the two deep boreholes (4.3 km and 4.2 km) at Pohang.

Following the three previous hydraulic stimulations at this site, the DESTRESS team, composed of international experts, conducted hydraulic stimulation (soft stimulation as we call it) in August 2017, followed by flowback of 100% of the injected water (see the DESTRESS newsletter). This treatment did not induce any seismic activity larger than magnitude 2.0. It was followed by additional injections, which ended on 18 September, two months before the recent Pohang earthquake. No larger seismic events were observed during this treatment, either.

Nonetheless, the DESTRESS team is willing to collaborate with Korean partners and authorities to investigate the possible link between the 15 November earthquake and the previous injection activities at Pohang.”

According to local news, geologists and seismologists said it is possible that the earthquake in Pohang was affected by activities on a geothermal project nearby, but this will probably not to be confirmed as the actual cause of the earthquake.

“Injecting water into the earth can reduce friction on a fault line, causing movement and potentially triggering a major earthquake in an area that is already under pressure. There have been steady reports of similar incidents overseas,” said Lee Jin-han, a professor at the department of earth and environmental science at Korea University.

“The fact that a small amount of water was injected at the geothermal plant at Pohang and that a large number of micro-earthquakes had occurred previously prevent us from concluding that the Pohang earthquake occurred because of the geothermal plant,” said Hong Tae-gyeong, a professor in the department of earth system science at Yonsei University. The Pohang geothermal plant has injected a total of 12,000? water on four or five occasions since 2016 and then removed some of that water, and currently about 5,000? remains underground.

Source: DestressThe Hankyoreh