The increase in number and strength of shallow induced seismicity connected to the Groningen gas field since 2003 and the occurrence of a ML 3.6 event in 2012 started the development of a full probabilistic seismic hazard assessment (PSHA) for Groningen, required by the regulator. Densification of the monitoring network resulted in a decrease of the location threshold and magnitude of completeness down to ∼ ML =0.5. Combined with a detailed local velocity model, epicentre accuracy could be reduced from 0.5–1 km to 0.1–0.3 km and a vertical resolution ∼0.3 km. Time-dependent seismic activity is observed and taken into account into PSHA calculations. Development of the Ground Motion Model for Groningen resulted in a significant reduction of the hazard. Comparison of different implementations of the PSHA, using different source models, based on either a compaction model and production scenarios or on extrapolation of past seismicity, and methods of calculation, shows similar results.
Bernard Dost, Elmer Ruigrok & Jesper Spetzler. Development of seismicity and probabilistic hazard assessment for the Groningen gas field
published, Netherlands Journal of Geosciences, 2017