Production-induced seismicity indicates a low risk of strong earthquakes in the Groningen gas field

The maximum possible earthquake related to gas production in Western Europe's largest gas field, Groningen, Netherlands, is an urgent practical question. Here we show how to distinguish between induced and triggered tectonic earthquakes. We estimate the maximum possible induced magnitude in the Groningen gas field to be around Mw = 4. We extend the concept of the seismogenic index to gas-production, and calculate the worst-case probability of triggering a larger-magnitude tectonic earthquake in a continuum. The probability of a Mw5.5 earthquake at Groningen is significantly higher than at Pohang Geothermal System (South Korea), where a Mw5.5 earthquake was actually triggered. Due to a long history of production in Groningen, our model estimates that strong earthquakes (Mw ≥ 4) must have occurred there several times, in disagreement with the observations. This indicates that the Groningen gas field is inherently stable and the physical conditions to trigger large tectonic earthquakes likely do not exist.