A finite element variational method is described and applied to plane strain analysis of zero frequency seismic data. This technique presents a suitable tool for the analysis of permanent displacements, tilts, and strains caused by seismic events, since it can model variable fault offsets in heterogeneous media. The accuracy of the technique is demonstrated by detailed static field computations for vertical and dipping dislocations acting in plane strain, corresponding to a fault of infinite length in a homogeneous half space, by comparison with closed form analytical solutions. A parametric study of material inhomogeneities and variable fault offsets reveals that order of magnitude changes in the solutions can occur for both near- and far-field displacements and strains. The technique was applied to the San Fernando earthquake. The best solution was obtained by separating the fault into two distinct parts, both parts having offsets near the surface a factor of 5 larger than the average slip. The seismic moment, defined in terms of the average displacement, is 6.2 × 1025 dyne cm, and the average stress drop is 24 bars for this fault system, although both stress drop and displacements vary by more than an order of magnitude along the fault plane, the maximum occurring at 1-km depth. Several solutions are investigated for the hypocentral region, one solution giving as much as 5 meters of offset. This possible behavior of the fault characterized by large variations of slip as failure progressed implies that local geology controlled this thrust fault through its effect on spatial distribution of prestress.