Nondimensional control parameters governing the behavior of one-dimensional fault slip:Effects of shear heating, inelastic pore creation, and fluid flow

摘要

We theoretically study the dynamic slip of a one-dimensional fault considering thermoporoelastic effects including shear heating, fluid flow, and inelastic pore creation. We find that the qualitative nature of system behavior can be understood in terms of three nondimensional parameters: S_u, S_u~', and P_0~*. The parameter Su represents the relative dominance of the effect of inelastic pore creation on the fluid pressure change over that of shear heating, while S_u~' is associated with the dominance of the fluid flow effect over the effect of shear heating. The parameter P_0~* denotes the initial fluid pressure. We observe the slip-weakening and slip-strengthening behaviors in the ranges S_u < —P_0~* and S_u> respectively, irrespective of the value of S. We can understand both fast and slow fault slips comprehensively on the basis of our model. Ordinary high-speed fault slip can be simulated with Su slightly larger than —P_0~*, S_u~' near the lower limit, and σ_s~0~ 100 MPa. We need the conditions of S_u —P_0~*, sufficiently large values for S_u~', and sufficiently smaller values for o to model much slower fault slip. Our present study also provides a model for the mechanism of negligible frictional heating on the San Andreas fault. We actually found that the temperature rise on the fault is negligibly low in the range of slip strengthening if the values of σ_s~0, and S_u~' are small enough and/or the value of S_u is significantly larger than a threshold.