Chapter 2 Fabrics of Experimental Fault Zones: Their Development and Relationship to Mechanical Behavior

摘要: Abstract The fracture array of simulated fault zones is shown to evolve in a predictable and reproducible manner, from stepwise fashion steady-state condition. At low confining pressures increasing shear strain the sequence is: (1) Homogeneous shearing by grain-to-grain movements. (2) R 2 - 1 -fractures initiate at about same time but propagate only few grain diameters. They are relatively high angles gouge-forcing block interface widely spaced. These first two stages one primarily gouge compaction characterized hardening. (3) Extension S coincident reorientation lower closely paralleling with forcing blocks. P-fractures initiate. occur ultimate strength through softening stage. (4) Y-fractures form along which most displacement accommodated, now close steady state. Y's initially or both interfaces blocks, shift interior gouge. this stage, sliding may change stable slip periodic oscillations, characteristic stick-slip sliding. development interpreted be result stress field across within zone. Riedel shears response Coulomb failure, appear as kinematic constraint produced more rigid bounding Modeling weak zone stronger medium shows that rotate higher boundaries. This consistent recent observations. A significant implication without recognition, laboratory values frictional coefficients overestimated.