In situ stress measurements on the San Andreas fault are modeled in terms of a solution to the equations of three-dimensional elastic equilibrium in a layered medium. Crustal stresses are expressed in terms of surface deformations. In particular, vertical stress gradients are shown to be proportional to horizontal gradients of vertical surface deformation. In light of constraints derived by this relation it is proposed to reinterpret the observed near surface in situ vertical stress gradients on the San Andreas fault as partly a manifestation of a layered crust with vertically increasing rigidity. Extrapolation to depth of the revised stress gradients suggests that the San Andreas fault can be regarded as a low-stress phenomenon compatible with estimates of shear stress obtained from heat flow data.