Discrete Element Modeling of Stick-Slip Instability and Induced Microseismicity

• Author(s) / Creator(s)

  • Khazaei, Cyrus

• Using Particle Flow Code (PFC3D), a discrete element model is presented in this paper that allows direct modeling of stick-slip behavior in pre-existing weak planes such as joints, beddings and faults. The model is used to simulate a biaxial sliding experiment from literature on a saw-cut specimen of Sierra granite with a single fault. The fault is represented by Smooth Joint Contact Model. Also, an algorithm is developed to record the stick-slip induced microseismic events along the fault. Once the results compared well with laboratory data, a parametric study has been conducted to investigate the evolution of model’s behavior due to varying factors such as resolution of the model, particles’ elasticity, fault’s coefficient of friction, fault’s stiffness and normal stress. The results show a decrease in shear strength of the fault in the models with smaller particles, smaller coefficient of friction of the fault, harder surrounding of the fault, softer faults and smaller normal stress on the fault. Also, a higher rate of displacements was observed for conditions resulting in smaller shear strength. An increase in b-values was observed by increasing the resolution or decreasing the normal stress on the fault while b-values were not sensitive to changes in elasticity of the fault or its surrounding. A larger number of recorded events were observed for the models with finer particles, smaller fault's coefficient of friction, harder fault’s surrounding, harder fault and smaller normal stress on the fault. The results suggest that it is possible for the two ends of a fault to be still while there are patches along the fault undergoing stick-slips. Such local stick-slips seem to provide a softer surrounding for their neighbour patches facilitating their subsequent stick-slips.

• Date created

  2016

• Subjects / Keywords

  • Keywords: Stick-slip
  • Particle Flow Code (PFC)
  • Microseismic
  • Fault Instability

• Type of Item

  Article (Published)

• DOI

  https://doi.org/10.7939/R3428T

• License

  Attribution 3.0 International