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

Abstract

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: Su, 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 Su < −P*0 and Su > −P*0, respectively, irrespective of the value of S′u. 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 σs0 ∼ 100 MPa. We need the conditions of Su ≫ −P*0, sufficiently large values for S′u, and sufficiently smaller values for σs0 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 σs0 and S′u are small enough and/or the value of Su is significantly larger than a threshold.