2018 has started off with an unpleasant bang in the province of Groningen: on Monday, 8 January, a 3.4 magnitude earthquake struck 25 miles above the city. There were reports of shaking across the province, including in the city itself. Thousands of tremors have hit the province in the past 20 years as a result of natural gas extraction operations. Production has been severely reduced in recent years in an effort to cause fewer quakes, but the quake on Monday was the third strongest yet to be measured in the province.
The location of most of the gas is relatively shallow, and with little forestation and only small clusters of developed areas, there is not much on the surface to absorb the impact of the earthquakes in the province. When they do happen, their impact can be felt many kilometers away from the epicenter.
When the Slochteren gas field was discovered in 1959, it was not immediately clear just how large the natural gas reserve was. Three kilometers underground lie a 2.8 trillion cubic meter gas field contained by the sandstone above: the reservoir is naturally sealed by the geological development of a layer of salt. Gas extraction operations occurred in Groningen for 20 years without any induced earthquakes, but according to figures from the Dutch meteorological organization KNMI, there have been 1,470 earthquakes in the Netherlands since 1986: on Christmas Day of that year, a 2.8 quake struck in Assen.
The quakes were relatively rare at first. Between 1986 and 1990, there were only three recorded quakes. But starting in the ‘90s, they were detected more frequently: there were 4 in 1991, 6 in 1992, and 16 in 1993. Twenty years later, the quakes had become so frequent that there was one earthquake every three days on average: there were 133 confirmed earthquakes in 2013. Of those, 121 occurred in the province of Groningen. That year coincided with the largest amount of extracted gas – 53.9 billion cubic meters – since the quakes became a common occurrence.
Nine quakes have been measured above 3.0 on the Richter scale since 2001. The biggest measured quake so far – 3.6 – occurred in 2012 in Huizinge. The quake on January 8 is the largest quake since then. Starting in 2013, the Dutch government called for the gas production operations to pump the brakes in an effort to prevent more earthquakes. The government has capped the operations at the Groningen gas field to 24 billion cubic meters per year through 2021. But despite only 19.3 billion cubic meters being extracted in 2017, there were actually even more induced earthquakes registered than in 2013. That does not necessarily mean there were more of these smaller quakes: NAM’s detection and measurement network was upgraded in 2014, which made it easier to detect activity below 1.5.
Friesland and Drenthe
Groningen is not the only Dutch province where gas extraction occurs. Friesland and Drenthe also have sites where natural gas is extracted or refined, including in the vicinity of the Wadden Sea. But roughly half of all the natural gas used in this country comes from the Slochteren gas field in the province of Groningen. Natural gas is a highly common energy source across the Netherlands: 40 billion cubic meters are used domestically in the Netherlands annually on average. Natural gas is more or less just methane – only ten percent of natural gas consists of other gases. Methane can trap significant amounts of heat in its unburned form, and a considerable quantity can escape during extraction and transportation.
Fifty years of extraction have resulted in roughly 1,700 billion cubic meters of gas being pumped out of the ground thus far, which is about two-thirds of the total estimated amount held in the reservoir. Extraction operations in the gas field in Groningen are run by the Dutch Petroleum Company (Nederlandse Aardolie Maatschappij BV), better known as NAM. NAM is co-owned by Royal Dutch Shell and ExxonMobil. Roughly 1,800 employees work for NAM, but most of the facilities across Groningen are largely unmanned: the majority of those jobs are at NAM’s headquarters in Assen, in the northern province of Drenthe.
Over the past 50 years, revenue from the extraction, refinement, storage, transportation and sales of natural gas in the Netherlands is estimated to be above 250 billion euros, which has been primarily reinvested in infrastructure, including tunnels, train tracks, upgrades to Dutch highways, water management, train stations and urban development initiatives. NAM has set aside 1.2 billion euros to compensate the thousands of people living in the earthquake-prone areas of Groningen, but the historic brick farmhouses dotting the previously peaceful landscape were not built to withstand sustained seismic activity. Many structures have been so severely damaged that they have been condemned or torn down. According to an investigation by Dagblad van het Noorden, 89 buildings have been demolished as a result of the gas extractions, and an additional 372 buildings are listed as vulnerable. Children from two elementary schools in the town of Loppersum have to attend classes elsewhere because their schools were deemed unsafe: one of the schools, Prinses Beatrix, was torn down in 2017.
In 2016, research from the University of Groningen estimated that up to 100,000 people in the province had suffered damage from the quakes. While the persistent quakes have taken a toll on the residents of the province mentally, financially and emotionally, as far as has been made publicly known, no injuries or deaths have directly resulted from the manmade quakes. But the locals are not taking it lying down: a handful of fierce activist groups (Groninger Bodem Beweging, Groningers in Opstand, Schokkend Groningen, among others) have cropped up over the past ten years, organizing torch-lit marches, tractor-filled demonstrations, and protesting at gas extraction sites throughout the province.