Unstable stick-slip events have been confined to a portion of a finely ground, 40- by 200-cm simulated fault in a granite sample by selectively injecting water onto the ends of the stressed fault. Source parameters of eight confined events generated at normal stresses between 0.7 and 4.1 MPa have been measured. Dynamic stress drops increased from 0.06 to 0.38 MPa with increasing normal stress such that the ratio of stress drop to normal stress is about 0.09. Fractional shear stress drops of these events are less than 0.2. Total fault slip measured at the center of the slipped portion ranged from 8.5 to 38.9 &mgr;m. Maximum relative slip velocities at the same location ranged from 2.5 to 34.7 cm/s. Slip velocity increased with increasing dynamic stress drop.