The Effect of Clay Content on the Dilatancy and Frictional Properties of Fault Gouge

Mature fault cores are comprised of extremely fine, low permeability, clay-bearing gouges. Saturated granular materials known to dilate in response increases sliding velocity, resulting significant pore pressure drops that can suppress instability. Up now, dilatancy has been measured predominantly clay-poor Clay minerals have frictional strengths and, previous experiments, even small proportions clay were shown affect the properties a fault. It is important, therefore, document detail impact proportion on behavior and rocks. In this work, suite triaxial deformation experiments elucidated saturated, synthetic quartz-clay (kaolinite) gouges at effective normal stresses 60, 25, 10 MPa. Upon 10-fold velocity increase, all clay-quartz contents displayed measurable with samples yielding comparable changes studies. Peak dilation did not occur pure quartz gouges, but rather containing 40 wt% clay. The content simulated was found control gouge strength stability slip. A transition occurred ∼40 from strong, unstably quartz-dominated weak stably clay-dominated These results indicate clay-rich zone, volume could generate pore-fluid transients, contributing arrest earthquake nucleation or potentially promotion sustained slow