Modelling seismicity pattern of reservoir-induced earthquakes including poroelastic stressing and nucleation effects

Abnormal seismic activities near reservoirs usually show a strong spatiotemporal correlation with the water filling history. Reservoir-induced seismicity is thought to be related to crustal pore pressure and stress changes caused by water impounded behind the dams. Though the Coulomb-type stress analysis helps illuminate areas that would be under risk following reservoir impoundment, it lacks the ability to explain the temporal characteristics of reservoir-induced seismicity. We present a numerical investigation of the seismicity rate evolution of reservoir-induced earthquakes. Our modelling employs a fully coupled 2-D poroelastic model to calculate the pore pressure and stress changes caused by water impoundment and incorporates the rate- and state-dependent friction law to investigate the seismicity rate. We demonstrate that shallow earthquakes are mainly caused by pore pressure increase, while poroelastic stress transfer takes the dominant role at depth. Whether a fault would be brought close to failure depends on its geometrical properties and its relative location to the reservoir. The temporal evolution of reservoir-induced earthquakes is primarily controlled by tectonic environment instead of the diffusion of pore pressure.