Crystal defect theory is employed to predict residual displacement fields resulting from faulting in a semi-infinite, isotropic elastic medium. The description of faulting structures should consider not only translational but also rotational movements. The concept of rotational defects, also known as disclinations in crystal physics, can be employed to treat the problem of rotational fault movements. The combination of dislocation and disclination theories completes the physical concept necessary to describe fault movements in general. Four examples of rotational faults have been identified in geological literature. Furthermore, a model for fault surfaces involving circular and semicircular disclinations and dislocations is proposed. The model permits any falut orientation and location relative to the ground or free surface. The characteristics of translational and rotational faults are illustrated by the contour maps of displacements at the free surface for vertical strike slip and rotational faults. Comparisons between this model and existing analyses and field observations are favorable. It is proposed that this model can assist in defining the geometry of fault planes.