Fluid‐rock reaction weakening of fault zones
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The presence of weak phyllosilicates may explain the low shear strengths of fault zones if they define well-developed fabrics. The growth of phyllosilicates is favored in meteoric water-dominated granitic fault systems. Where phyllosilicates precipitate in active fault zones, they contribute directly to reaction softening. Because low-temperature deformation of phyllosilicates is not governed by frictional processes alone but can occur by pressure-independent dislocation glide, the strength of phyllosilicate-rich fault rocks can be low at all depths. Low strain rate creep during interseismic periods can align phyllosilicate grains in foliated gouge and phyllonites. Where preferred orientations are strong and continuity of phyllosilicates is large, strengths of rocks within fault zones may approach minimum strengths defined by single phyllosilicate crystals. -from Authors
author list (cited authors)
Wintsch, R. P., Christoffersen, R., & Kronenberg, A. K.