Impact of fault permeability anisotropy on the nucleation and rupture of injection-induced earthquakes

This study investigates the impact of fault permeability anisotropy on the nucleation and rupture of injection-induced earthquakes. Using numerical models, we analyze the effects of varying fault permeability in both, transverse and longitudinal directions. Our research focuses on understanding how these hydraulic properties influence the onset of slip, the nucleation length, and the propagation of the rupture. We simulate more than 400 cases with different combinations of friction parameters and hydraulic properties, verifying that the reference scaling L infinity = b G ' Dc n provides satisfactory results for scaling (b-a)2 o ' nucleation length. Our findings indicate that increased fault permeability delays the onset of slip and affects nucleation patterns, with high longitudinal permeability promoting larger nucleation lengths and high transverse permeability resulting in longer nucleation times. During rupture propagation, poroelastic effects cause undrained responses in pore pressure, significantly affecting the fault strength. Permeable faults exhibit more symmetrical rupture patterns and higher seismic moments than impermeable faults. The study highlights the crucial role of hydraulic properties in the development of nucleation and rupture of induced earthquakes, emphasizing the importance of these properties for designing safer injection protocols.