Magnitude 5.4 earthquake in South Korea
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. 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.