We perform an exhaustive study of coseismic and postseismic surface deforma
tions induced by shear dislocations using flat and spherical Earth:models.
Our aim is to examine the effects of the spherical geometry, the vertical l
ayering, and the self-gravitation on surface displacement field. For a 100
km long fault, spherical and flat models produce comparable coseismic defor
mations up to a distance of similar to 300 km from the epicenter. This dist
ance is sensibly reduced in the postseismic regime and when infinitely long
strike-slip faults are considered. The differences between predictions bas
ed on hat and spherical models are due both to their global geometry and th
e effect of the gravity forces. Self-gravitation has a minor role with resp
ect to that of sphericity for surface coseismic deformations, while in the
postseismic regime its effects increase considerably. As a case study, we c
onsider the coseismic and postseismic deformations due to the great 1960 Ch
ilean earthquake. The results of the spherical stratified model differ sens
ibly from those of a flat uniform model. Moreover, within the framework of
spherical Earth models, the rheological stratification plays a major role i
n determining the pattern of the displacement field. We show that the prese
nt-day rates of vertical and horizontal deformations are considerably large
(similar to 10(-2) m yr(-1)) for an asthenospheric viscosity ranging from
10(19) to 10(20) Pa s. These rates, which could possibly be detected by geo
detic investigations, are found to be also sensitive to the rheological pro
perties of the mantle beneath the asthenosphere.