Small Earthquakes Matter in Injection‐Induced Seismicity

Abstract

AbstractA simplistic triggering mechanism, pore pressure increase from injection, has been the focus of injection‐induced seismicity studies for decades. Research into other possible mechanisms, like poroelastic stress changes, is ongoing, but there has been relatively little focus on earthquake interaction. While studies have looked at how moderate‐magnitude events (M ≥ 3.0) may trigger larger magnitude‐induced seismicity, research into the cumulative effect of the hundreds to thousands of small‐magnitude (M ≤ 3.0) events is lacking. Here we use generic models to compare the possible stress changes from pore pressure increase and from earthquake interactions of small‐magnitude events. We find that the area of increased pore pressure is much larger than that of positive Coulomb static stress transfer; however, maximum Coulomb static stress change is larger than maximum pore pressure increase. We argue that, yes, small earthquakes do matter, and their interaction may be an important triggering mechanism to consider.