This study aims to demonstrate the capability to account for seismic and aseismic responses due to fault reactivation using a cohesive zone model in a Finite Element framework. We adopt an elastic-damage-plastic formulation to predict the fault reactivation while considering unilateral effects observed in geomaterials. In a conceptual 2D problem representing two layers of rock separated by an existing fault, we apply displacement-driven and stress-driven shear loading to provide a first characterization of the instabilities and energy dissipation. Qualitative and quantitative analyses of the dissipative process are provided through the shear stress field and the evolution of the shear stress, displacement, and energy balance. We obtain through the present model the total of dissipated energy thanks to the energy balance. Also, while the elastic energy variation can be positive or negative depending on the type of boundary conditions (stress-driven or displacement-driven), the radiated elastic energy is always positive during seismic events. It is so a good candidate to determine the seismic moment.


Instabilities in faulted mechanical systems are at the heart of numerous recent studies related to micro-seismic phenomena induced by human activities. Increasing interest to assess the potential for activation of existing faults in geologic sites has been observed in different applications such as CO2 sequestration (Nguyen et al., 2019), waste-water disposal (Walsh and Zoback, 2015), recovery of hydrocarbons (Davies et al., 2013), geothermal facilities (Majer et al., 2007) and nuclear waste disposal (Urpi et al., 2019). Several previous studies showed that both natural and anthropogenic factors determine fault reactivation phenomena (McGarr, 2014; Segall and Lu, 2015; Fan et al., 2016). The lack of long-term historical monitoring of seismic activity in candidate sites to host in-deep geological applications is an important drawback to assess the risks through empirical models. For this reason, numerical models were mainly used to predict fault reactivation response (e.g. finite element method (Haddad and Eichhubl, 2020), discrete element method (Langhi et al., 2010), finite difference method (Lee et al., 2013)).

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