A magnitude-5.4 earthquake that struck the South Korean city of Pohang on 15 November 2017 was probably triggered by an experimental geothermal power plant injecting water a few kilometres underground, a research team reports. A second independent analysis also finds the plant’s involvement to be plausible.

The pair of studies, published online on 26 April in Science¹^,², heighten scrutiny of the potential role of the geothermal plant in the quake, which was South Korea’s second-strongest since observations began in 1978 and the most destructive ever recorded in the country. Eighty-two people were injured and more than 200 homes were seriously damaged.

Earthquakes of similar magnitude in Oklahoma have been linked to the injection of wastewater from hydraulic fracturing (fracking). But the Pohang quake is by far the strongest ever linked to a geothermal power plant — 1,000 times mightier than a magnitude-3.4 earthquake caused by a similar plant in Basel, Switzerland, in 2006.

The findings could shake up the global geothermal industry, the researchers say. “If the Pohang earthquake is really induced, it’s a kind of game-changer in the hydro-geothermal power plant industry,” say Jin-Han Ree, a structural geologist at Korea University in Seoul, and a lead author on one of the studies¹.

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[…] In the past decade, states such as Oklahoma have seen a spike in induced earthquakes, because of the injection of wastewater from hydraulic fracturing operations. However, unlike the fracking operations, the water from enhanced geothermal power does not stay underground or cause a long-term buildup of pressure. That has prompted some scientists to base earthquake risk assessments for geothermal operations largely on how the wells are operated, including the amount or rate of liquid injected. …