B‐Value Evolution During the Strasbourg 2018–2022 Sequence of Induced Earthquakes

This is the authors' abstract. We don't add key points for this paper.

The b‐value, defined as the slope of the cumulative earthquake frequency–magnitude distribution in semi‐logarithmic space, quantifies the relative occurrence of small and large earthquakes. It is a key metric for hazard assessment and is often used in adaptive traffic light systems to mitigate induced seismicity. In this study, we analyze a 4‐year sequence of induced earthquakes at the Vendenheim geothermal site near Strasbourg (France), where multiple sequential operations were carried out near a regional fault zone, to explore the spatio‐temporal variability of the b‐value during fault activity. Our analysis highlights the importance of spatial clustering in understanding b‐value variability. Despite occurring in close spatial and temporal proximity, seismicity clusters exhibit markedly different b‐values. The clusters with the lowest b‐values host the largest magnitude events (). Even when significant seismic migration is observed within the clusters, their b‐value remains relatively constant over time. The observed temporal fluctuations in the b‐value of the entire induced seismicity population are shown to be closely related to the relative activity of each cluster over time. We propose that b‐value variations, along with the observed seismicity migration, are related to inherited spatial variability in the geomechanical properties of faults rather than to the dynamic evolution of stress conditions.