Earthquake Nucleation Characteristics Revealed by Seismicity Response to Seasonal Stress Variations Induced by Gas Production at Groningen

Deterministic earthquake prediction remains elusive, but time-dependent probabilistic seismicity forecasting seems within reach thanks to the development of physics-based models relating seismicity to stress changes. Difficulties include constraining the earthquake nucleation model and fault initial stress state. Here, we analyze induced earthquakes from the Groningen gas field, where production is strongly seasonal, and seismicity began 3 decades after production started. We use the seismicity response to stress variations to constrain the earthquake nucleation process and calibrate models for time-dependent forecasting of induced earthquakes. Remarkable agreements of modeled and observed seismicity are obtained when we consider (a) the initial strength excess, (b) the finite duration of earthquake nucleation, and (c) the seasonal variations of gas production. We propose a novel metric to quantify the nucleation model's ability to capture the damped amplitude and the phase of the seismicity response to short-timescale (seasonal) stress variations which allows further tightening the model's parameters. Earthquakes are difficult to predict with certainty, but progress in forecasting their likelihood using probabilistic models based on stress changes has been made. However, challenges remain in understanding how earthquakes start and the initial conditions of faults. Here, we analyzed induced earthquakes in the Groningen gas field, where production is seasonal and seismic activity began 34 years after gas production started. By studying how the earthquakes respond to rapid changes in stress, we could better understand how they start and develop models to forecast their temporal occurrence. By considering factors like the initial strength of the faults, the duration of earthquake initiation, and seasonal variations in gas production we could accurately match the observed seismic activity. We introduced a new measure to evaluate how well the models captured the dampened strength and timing of seismic activity in response to short-term stress changes (such as seasonal variations), which helped refine the model's parameters. An improved reservoir, geomechanical, and seismicity modeling workflow is proposed for forecasting induced seismicity at various timescalesShort-timescale stress variations allow constraining the characteristics of the earthquake nucleation process using Groningen as case studyInitial strength excess and finite duration of the nucleation process allow reproducing long-and-short timescale characteristics of seismicity