Variance-based sensitivity of stress inversion of focal mechanims

The target of sensitivity analysis is the identification of the variability contribution in inputs to the variability in outputs. Focal mechanism stress inversion uses focal mechanism to retrieve principal stress axis and stress ratio. These parameters are used to calculate maximum horizontal stress (SH) and the instability criterion. Studying the variability contribution of input factors help increased understanding of the connections between input and output variables of the model. We investigate the sensitivity of SH and instability criterion to strike, dip, and rake and friction for stress inversion by focal mechanisms.The results show that SH is more sensitive to the interaction of strike and rake than dip so it has less importance. The value of global sensitivity index is 0.77 for that interaction. The instability criterion to measure fault instability of fault orientations is more sensitive to the interaction between dip and rake and then to friction with global sensitivity of 0.396e-4 and 0.299e-4 respectively. We also studied the importance of input factors in Mohr-Coulomb failure criterion. Pore pressure and friction with the values of about 0.5 and 0.1 are the most important factors.