We derive a continuum rheology for the deformation of the continental crust using continuum damage mechanics. It is hypothesized that when a constant strain rate $dot{varepsilon}$ is applied to a solid material, the stress σ and damage increase until failure occurs, which is analogous to an earthquake. We further assume that this process is repeated, in analogy to the reoccurrence of earthquakes on a fault. Our model assumes that the continental crust behaves elastically below a yield stress σy. Above this stress the continuum deformations can be modeled as a non-Newtonian viscous flow with $dot{varepsilon}$ $propto$ (σ - σy)n, where n is constant. We derive the modified Omori's law for aftershock decay using a viscoelastic version of our model and get good agreement with observations taking n = 6. Using parameter values appropriate for aftershocks, we obtain a continuum crustal rheology that can explain major orogenies such as the Indian-Asian collision.