Figure 8

( a − b ) or (∆ μ _ss /∆ln V _sliding ) plotted against clay-mineral content for the five samples tested in this study. Values of (a − b) (squares) and ratios of incremental steady-state friction coefficient to incremental logarithmic sliding velocity (∆μ_ss/∆lnV_sliding) (circles) are plotted against the content of clay minerals. Squares with vertical bars indicate average and standard deviation values of (a − b) values plotted in Figure 5, while circles with vertical bars indicate ∆μ_ss/∆lnV_sliding values and their errors from the least-squares fit shown in Figure 6.