Figure 2.

(a) Results from three multiple-velocity step experiments: 3 mm/s for ∼6 cm of displacement, acceleration to ∼4.5 m/s, and deceleration to rest. The approximate thermal-weakening distance (D_th) and slip-weakening distance (D_w) are indicated for Run 735 (see text for details). Stars indicate the displacement at which the friction rapidly decreases; the corresponding velocity (falloff velocity) is shown in Figure 2b. (b) Frictional stick-slip instabilities observed in Run 735 at 3 mm/s. (c) The imposed velocity profiles for experiments shown in Figure 2a. Note that the acceleration is very similar in both gouge and bare surface experiments.