Can the Nucleation Phase be Generated on a Sub-fault Linked to the Main Fault of an Earthquake?

Abstract. We study the effects of seismic coupling, friction, viscous, and inertia on earthquake nucleation based on a two-body spring-slider model in the presence of thermal-pressurized slip-dependent friction and viscosity. The stiffness ratio of the system to represent seismic coupling is the ratio of coil spring K between two sliders and the leaf spring L between a slider and the background plate and denoted by s = K/L. The s is not a significant factor in generating the nucleation phase. The masses of the two sliders are m₁ and m₂, respectively. The frictional and viscous effects are specified by the static friction force, f_o, the characteristic displacement, U_c, and viscosity coefficient, h, respectively. Numerical simulations show that friction and viscosity can both lengthen the natural period of the system and viscosity increases the duration time of motion of the slider. Higher viscosity causes lower particle velocities than lower viscosity. The ratios γ = h₂/h₁, φ = f_o2/f_o1, ψ = U_c2/U_cl, and μ = m₂/m₁ are four important factors in influencing the generation of a nucleation phase. When s > 0.17, γ > 1, 1.15 > φ > 1, ψ < 1, and μ < 30, simulation results exhibit the generation of nucleation phase on slider 1 and the formation of P wave on slider 2. The results are consistent with the observations and suggest the possibility of generation of nucleation phase on a sub-fault.