The great (Mw=9.3) Valdivia earthquake of May 21--22, 1960, was associated with ground deformation over a distance of over 800 km parallel to the Peru-Chile trench. Downwarping by as much as 2.3 m affected a belt averaging a width of 100 km which was bordered by a major upwarped zone in the west, where uplift locally attained 5.7 m, and a minor upwarped zone in the east. The deformation has been explained by thin viscous sheet models or by dislocation models involving predominantly dip-slip movement on thrust faults. We show that it can be modeled by elastic buckling of the overriding South American plate without the need to invoke specific fault geometries. The proposed buckling mechanism accounts for both zones of upwarping and for the exceptionally rapid uplift experienced by Mocha Island to the west. Moreover, elastic relaxation provides a simple explanation for the postseismic recovery reported by observers at several sites. It is also consistent with the results obtained by 14C dating of fossil shorelines within the outside the area affected by the 1960 events, which show that central and northern Chile has undergone little uplift during the last 30,000 years despite convergence between the South American and Nazca plates at over 90 mm/yr, although the presence of numerous older shorelines shows that coastal uplift was very active earlier in the Cenozoic. ¿ American Geophysical Union 1994