Repeated leveling surveys conducted in 1938, 1967, 1975--1976, 1980, and 1981 provide information on preseismic, coseismic, and postseismic movements associated with the Ms~7.3 1977 Caucete, Argentina, earthquake sequence. The spatial pattern and amount of uplift (~1 m) that accompanied the earthquake suggest 4 m of slip on a north-south trending, west dipping fault, buried 17 km below the surface, with a dip of 35¿, a downdip width of 24 km, and a length of 80 km.

These fault parameters are generally consistent with the seismic focal mechanism, the moment of double main shock, and the distribution of aftershocks. Vertical movements during the first preseismic period (1938--1967), while an order of magnitude smaller, have a spatial pattern similar to the observed coseismic movements. The second period of preseismic deformation (1967--1976) is characterized by movements opposite those which accompanied the earthquake (~2*1 cm of relative subsidence). During the first postseismic interval (1978--1980), deformation continued in the same sense as the coseismic movements (an additional 10¿1 cm of relative uplift). Subsequent postseismic movements (1980--1981) were opposite in sense to the coseismic deformation (~12¿1 cm of relative subsidence). We suggest that the preseismic movements for the 1938--1967 time period result from reverse slip (~50 cm) on a downdip section of the 1977 earthquake fault. This slip may have been induced by a M3~7.5 earthquake that occurred near San Juan in 1944 or may represent coseismic slip for a M~6.5 earthquake that occurred in 1941.

Deformation during the second preseismic period (1967--1976) is interpreted as being due to steady strain accumulation on the fault (~9 mm yr-1). The initial postseismic movements (1978--1980) are roughly consistent with afterslip on the 1977 earthquake fault (~40 cm) in the same sense as the coseismic slip. The second phase of postseismic deformation may represent the period of rapid post-seismic recovery (i.e., strain accumulation) observed previously in interplate areas. There is some evidence that strain accumulation following the earthquake began on the updip section of the fault. This process of strain accumulation may be responsible for the fact that the 1977 main shock initiated at the updip end of the coseismic fault. Assuming that the time predictable model of earthquake occurrence is applicable to this area, we estimate that the next earthquake on the 1977 earthquake fault will occur in 200--600 years.