The elasticity theory of dislocations is used for sources with Burgers' vector normal to the dislocation surface. It leads to a source model for an opening crack consisting of a center of dilatation and a double force without moment. The work on deformations around a tension crack in a homogeneous half-space is combined with the results for subsurface deformations in a layered half-space. Thus, a method is obtained to calculate the displacements and stress throughout a medium accounting for vertical changes in its elastic parameters. By superposition of the elastic field of point sources, an extended crack or a system of crack can be simulated. The results agree very well with those for inclined cracks point sources in a homogeneous half-space. Surface displacements subsurface displacement and tilt fields obtained for realistic situations are measurable by existing methods. The influence of layering is demonstrated in comparison with homogeneous models and the results of a model consisting of several point cracks are given. The method can be applied to the forward modeling of crustal deformation caused by dike injections in volcanic areas, by mid-ocean ridges, and by continental rifts. Thus, the so-called magma chamber of a volcano can be modeled as a system of cracks instead of a cavity. Moreover, the deformational effects of dilatancy in rock and the opening of cracks during hydrofracturing can be simulated. ¿American Geophysical Union 1993