Nucleation and rupture of induced earthquakes in Groningen confined to the gas reservoir due to lithological variations

Meng Li, André R. Niemeijer, Femke C Vossepoel, & Ylona van Dinther

Submitted September 7, 2025, SCEC Contribution #14485, 2025 SCEC Annual Meeting Poster #TBD

Seismic hazard assessment in Groningen (the Netherlands) requires understanding the earthquake nucleation and rupture induced by gas extraction. Despite significant instrument advancements, interpretations of seismological observations are often inconsistent because the focal depth inversion uncertainty (~300 m) is comparable to reservoir thickness (50-300 m). Two fault segments, the velocity-weakening anhydrite layer within the caprock sequence and the velocity-strengthening sandstone reservoir experiencing substantial healing, are suggested to be seismogenic [1] but their respective roles in nucleation and rupture remain unclear. Additionally, whether ruptures can propagate into the non-seismogenic over- and underburden layers is also debated, yet this is a key constraint for the maximum possible earthquake magnitude (Mmax).

We extend a rate-and-state friction-based earthquake sequence model [1] by incorporating heterogeneous stratigraphy and lithology-specific elastic and frictional properties derived from dense in-situ and laboratory measurements. Our simulations show that nucleation typically initiates within the velocity-strengthening, depleting reservoir and rupture remains largely confined to this layer, similar to previous homogeneous models [1]. Increasing the thickness of the velocity-weakening anhydrite layer does not promote nucleation or rupture within it. Ruptures may extend slightly, by a few tens of meters, into the bi-material interfaces annex to the reservoir boundaries created by fault offset, but further propagation is halted by a strong stress valley caused by lithological variations. Only under extreme conditions is this barrier overcome, and runaway rupture observed. Given variations and uncertainties in parameters and fault geometry, we conduct an extensive parametric study to test the sensitivity of rupture behavior to spatially variable parameters, such as reservoir thickness and fault offset. We find that the conditions required for runaway ruptures are stringent and unlikely to be fulfilled before complete reservoir depletion. These findings help constrain the potential rupture depth and Mmax in Groningen and similar clastic formations in NW Europe.

[1] Li, M., Niemeijer, A., Van Dinther, Y. (in review at Nat. Comm.) https://doi.org/10.21203/rs.3.rs-3317840/v1.

Citation
Li, M., Niemeijer, A. R., Vossepoel, F., & van Dinther, Y. (2025, 09). Nucleation and rupture of induced earthquakes in Groningen confined to the gas reservoir due to lithological variations. Poster Presentation at 2025 SCEC Annual Meeting.


Related Projects & Working Groups
Fault and Rupture Mechanics (FARM)