What was already strongly suspected has now been officially established: the three earthquakes in the Eleveld gas field were caused by gas extraction in the area. This is stated by the State Supervision of Mines (SodM) after research by the NAM.
The ground shook twice at Ekehaar in October with magnitudes of 2.2 and 1.3 on the Richter scale. In the same month, an earthquake was registered near Hooghalen. This had a magnitude of 1.9 on the Richter scale.
Supervisor SodM previously announced that the earthquakes are related to gas extraction. Since 1986, the KNMI has registered almost fifty earthquakes that turned out to be related to the pumping of gas at Eleveld. The last earthquake until last month was in 2014.
Two of the past three quakes were not noticed at all, the SodM writes. Only the heaviest, which was measured on October 29 near Hooghalen, was felt by a few.
The fact that (Northern) Drenthe earthquakes are less noticeable is due to sand in the soil. In Groningen, where earthquakes occur with the same force, peat and clay soil cause a so-called spiral effect.
The SodM and the NAM state that a drop in pressure is the cause of the earthquakes. Furthermore, ‘the locations of the earthquakes can be easily related to the fractures in and along the gas field’.
Since October 15 this year, the extraction of natural gas from the Eleveld has been halted due to planned maintenance. No relationship has been discovered between the work and the resulting earthquakes. The SodM sees no further need to scale back gas extraction in the Drenthe gas bubble.