Figure 2. (A) Shaded relief, active faults (modified from Quaternary Fault and Fold Database for the United States, http://qfaults.cr.usgs.gov/) of southern California and selected site velocities from the Southern California Earthquake Center Crustal Motion Map (CMM3; Shen et al., 2003). White triangles show all CMM3 sites in the region, and those we selected from the group have velocities shown by arrows (note the velocity scale at the bottom). The maximum velocity uncertainty is 4.6 mm/yr, but the maximum in the N40°W direction is 1.6 mm/yr. The clear velocity gradient across the SAF is shown in (B). The location of the VMR site is indicated by the star. (B) The N40°W parallel component of the selected CMM3 velocities is plotted with respect to distance from the SAF and relative to 0 mm/yr at the SAF. The two curves show modeled velocities for steady interseismic slip below 12 km and bracket most of the observed motion. At left, the slip-rate estimate from our study of 35.4 ± 8.8 mm/yr with uncertainties indicated by the white boxes is drawn for comparison.