We present a first-order method for modeling broadscale deformation consistent with both plate tectonic motions and elastic strain accumulation on plate boundary faults. Interseismic deformation is assumed to be a superposition of long-term rigid-body motions between faults, defined by angular velocities of spherical plates, and backslip on shallow locked portions of faults in an elastic half-space. This method is applied to 1993--2000 continuous GPS data from 35 sites in a profile from the San Francisco Bay area, northern California, to eastern Nevada. Deformation is consistent, within the 1 mm yr-1 uncertainties of the estimated site velocities, with a simple 10-parameter model using 6 rigid plates and 3 locked San Andreas system faults. ¿ 2001 American Geophysical Union