Testing self-organized criticality by induced seismicity

We examine the hypothesis proposed in recent years by several authors that the crust is in a self‐organized critical (SOC) state. This hypothesis has been suggested on the basis of the observation of power law distributions, such as the Gutenberg‐Richter law for earthquakes and the fault length distribution, and of the fractal geometry of sets of earthquake epicenters and of fault patterns. These self‐similar properties are shared by simplified models of the crust exhibiting a spontaneous organization toward a critical point characterized by similar scale‐invariant properties. The term “critical” is here used in the sense of phase transitions such as the Curie point in magnetism. The usefulness of a hypothesis is measured by its predictive and explanatory power outside the range of observations that have helped defined it. We thus explore how the SOC concept can help in understanding the observed earthquake clustering on relatively narrow fault domains and the phenomenon of induced seismicity. We review the major reported cases of induced seismicity in various parts of the world and find that both pore pressure changes (±Δp) and mass transfers (±Δm) leading to incremental deviatoric stresses of