Estimation of potential magnitudes of induced seismic events based on direct numerical simulation of fluid injection near an active tectonic fault.

The subject of this study is the process of hydraulic stimulation of a tectonic fault, leading to induced seismicity. We consider a scenario in which fluid injected near ​​an existing fault, causing a localized change in pore pressure and a reduction in effective stresses. This, in turn, initiates slippage of the fault segments and the formation of a slip zone, the size and slip velocity of which determine the magnitude of the resulting seismic events. The goal of this study was to develop a relatively simple model for estimating the potential magnitude of induced seismic events based on a limited set of governing parameters. The primary objectives of the study were to identify the key factors that have the greatest impact on the characteristics of the slip zone and to determine how fluid injection parameters (rate and injected fluid volume) affect earthquake magnitude by changing slip dynamics. The model obtained is based on the results of a series of numerical experiments analyzing the hydromechanical behavior of the fault under various injection conditions. The modeling was performed using a two-parameter rate-and-state friction law, which, unlike a single-parameter model, allows for a wider range of slip regimes to be simulated and accurately describes the transition from stable slip to dynamic failure.

The functional relationships were established between the initial system parameters and the key obtained slip characteristics. It was shown that the final slip zone length is almost linearly related to the length of the initial unstable zone, and the maximum slip velocity increases exponentially with increasing pore pressure rate. At the same time, in the area of high loading rates, the saturation of the sliding velocity is observed at a characteristic level, which leads to a limitation of the possible magnitudes of earthquakes induced by fluid injection.