Light earthquake in Usquert marks 2,000th quake in Groningen gas extraction area
A small earthquake struck near the village of Usquert in the province of Groningen Monday evening, registering a magnitude of 0.9, too minor to be felt by residents, KNMI reported. The tremor marks the 2,000th earthquake in the Netherlands linked to natural gas extraction. The first such quake was recorded near Assen in 1986.
These human-induced tremors, known as induced earthquakes, have likely been far more numerous than official records suggest. Läslo Evers, a seismologist with the Royal Netherlands Meteorological Institute (KNMI), explained that early detection was limited, “In the early years, the few sensors could only register earthquakes with a magnitude of 1.5 or higher. Nowadays, there are more devices available, and they are more sensitive. Tremors of almost 0.0 are now recorded, whereas they previously went unnoticed.”
The majority of these earthquakes occur in the heart of Groningen, within the central Groningen gas field. The municipalities of Eemsdelta and Midden-Groningen alone have experienced more than 1,300 tremors—accounting for roughly two-thirds of all induced earthquakes in the country. “That is where the compaction of the gas reservoir is greatest and the ground subsidence is highest. That is also where the most stress has built up,” Evers said.
Most of the induced earthquakes are centered at a shallow depth of about 3 kilometers, which can make them feel stronger on the surface than their Richter scale magnitude suggests.
The cessation of gas extraction has reduced earthquake frequency. Last year, KNMI recorded 37 induced earthquakes, down from 42 the previous year. A decade or more ago, the number exceeded 100 annually. Evers noted: “You see a decrease in the number of earthquakes, but unfortunately, the risk remains. The subsurface has not yet stabilized; earthquakes will continue for years.”
He also emphasized that the potential for relatively strong quakes persists. “In November, there was still a 3.4-magnitude earthquake near Zeerijp. That was the third-strongest earthquake ever recorded in Groningen.” But most tremors remain minor. Nine out of ten recorded quakes were below magnitude 2.0, imperceptible to people.
Evers could not estimate when the earthquakes will cease. “Gas extraction began in the 1960s, and the first earthquake occurred around 1990. It took thirty years for enough stress to build up in the ground for earthquakes to occur. They increased over time and became stronger. No one knows how long it will take for them to stop.”
