Do Spatiotemporal Variations Exist in the Event-size Distribution of
Extraction-Induced Seismicity in the Groningen Gas Field?
Abstract
The scaling of event sizes is one of the critical parameters controlling
seismic hazard and risk. For induced seismicity, the non-stationary,
heterogeneous character of subsurface stress perturbations can be a
source of spatiotemporal variations in the scaling of event sizes. We
analyse the spatiotemporal variations in the earthquake-size
distribution of the Groningen induced seismicity catalogue using a
method that circumvents arbitrary choices requiring a priori knowledge
of these variations while systematically exploring the effect of
possible bias in the derivation. Our results show that the
b-value is spatially variable with indications of a temporal
decrease. This spatiotemporal pattern may be explained by a
stress-dependent b-value. At the same time, we postulate that the
event-size distribution is tapered at a single, regional corner
magnitude. Our results imply that the current risk assessment models
overestimate the probability of larger magnitude events (M≥3.5) in the
Groningen gas field and thus the risk posed.