A microphysical model for fault gouge friction applied to subduction megathrusts

摘要: A microphysical model is developed for the steady state frictional behavior of illite-quartz fault gouge and applied to subduction megathrust P-T conditions. The assumes a foliated, phyllosilicate-supported microstructure which shears by rate-independent slip on aligned phyllosilicates plus thermally activated deformation intervening quartz clasts. At low rates or high temperatures, clasts easy, accommodating foliation without dilatation. With increasing velocity decreasing temperature, shear becomes more difficult, bulk strength, until inclined portions phyllosilicate foliation, where it anastomoses around Slip at these sites leads dilation involving clast/matrix debonding, balanced, state, compaction through clast deformation. Model predictions, taking pressure solution as mechanism, show three regimes velocity-dependent temperatures in range 200–500°C, with weakening occurring 300–400°C, broad agreement previous experiments gouge. Effects rate, normal stress, fraction predicted also resemble those seen experimentally. Extrapolation earthquake nucleation successfully predicts onset velocity-weakening updip seismogenic limit megathrusts. further implies that seismogenesis controlled initiation rock quartz, counteracts dilatation due foliation.