To the present, dislocation theories for a homogeneous half-space are often used to calculate or interpret displacements and gravity changes caused by an earthquake or to inverse a seismic fault model. However, far-field effects of spherical curvature and radial heterogeneity have to be considered. In this research, Okada <1985> and Sun et al. <1996> dislocation theories are used to calculate displacements caused by four independent dislocations in three earth models: a homogeneous half-space, a homogeneous sphere, and a heterogeneous sphere. Effects of spherical curvature and radial heterogeneity are investigated through comparison of displacements. Results show that effects of both sphericity and stratification are very large. The stratified effect reaches a discrepancy of more than 25% everywhere on the surface of the earth, including the near field.