Morphotectonic Processes in Seismic Zones of Moderate Intensity, Argentina

Abstract

This study deals with the neotectonic deformation in seismic zones of moderate intensity in some areas of the Sierras Pampeanas, Santa Bárbara System and Chaqueña Plain of Argentina. In the study region, the location of earthquakes of ≥ three, ≥ four, and ≥ six Richter magnitudes agree with the traces of regional faults, evidencing their neotectonic activity. Seismic energy is generally transmitted over inherited faults, such as in the Metan basin. Minor new faults occur in Quaternary terraced deposits,and others move, taking advantage of the Neogene sedimentary strata. The folds are generally buried, but the younger sequences are gently undulating. The seismic energy dissipated through fewer cohesion materials that form the valleys' fill, developing discrete fault scarps and strongly folded conglomerate strata. The foothills deposits and basins absorbed most of the seismic energy released during the reactivation of the faults. Tectonic activity is deforming 630 BP deposits in the Cumbres Calchaquíes piedmont. Considering deformation values, neotectonic deformation in the outcrops and seismic profiles evidence, it is possible to interpret that the seismic activity in the study area from the Pleistocene to the present remained between the current records. This seismic activity, sustained over time, is sufficient to produce deformation in the foothills, reactivate pre-existing faults with small displacements and generate minor new faults in recent conglomeratic deposits. Many faults are blind. However, the deformation of the landscape and the modification of the drainage network are direct indicators of the activity of these structures.