Seismotectonic study in the Sierras de Velasco, Ambato, and Ancasti, Eastern Sierras Pampeanas of Argentina

Abstract

In this work, we study the seismic activity and tectonic regime in the region of the Sierras de Velasco, Ambato and Ancasti, belonging to the Sierras Pampeanas. These areas exhibit notable seismic activity, posing a considerable risk for populations in the region. We relocated the most important seismic events of the last twenty years and obtained their focal mechanisms. We reviewed the field evidence of neotectonic deformation, and measured kinematic indicators on Quaternary faults interpreted as seismogenic. Based on this information, we discuss the link between seismogenic sources and the most relevant morphostructural features. Our findings reveal that the seismicity is dominated by reverse focal mechanisms, exhibiting nodal planes with strikes that align with the main structures. This indicates that the main range-bounding faults are the most important seismogenic structures in the area. Some events have strike-slip movements, likely associated with the reactivation of basement fabrics. Additionally, in the Pirquitas area, we observed a normal focal mechanism, oriented perpendicular to the main structures. Our results contribute to a better understanding of current deformation dynamics and of seismic hazard in the region, and underscore the need for more detailed studies.