Definition of the Andean seismogenic-active front in the Malargüe fold and thrust belt using a local seismic network and gravity data

Abstract

This study focuses on the central sector of the Malargüe Fold and Thrust Belt (35.5◦ –36.5◦ S), where the limited crustal seismicity of the Payenia volcanic field and the presence of Quaternary deposits complicate the delin­eation of the neotectonic front and the identification of active structures. The deployment of a seismological network enabled the recording of local seismicity, revealing hypocenters clustered into two main groups in the upper crust, associated with NE–SW oriented basement structures. Focal mechanism analysis indicates a pre­dominance of dextral strike-slip faulting with subordinate reverse components, while gravity data link the earthquakes to the source bodies generating the main anomalies. Group A activity reflects deformation accommodated by dextral basement faults modulated by reverse motion, with implications for hydrocarbon migration and accumulation. Group B highlights the interaction between deep structures, upper-crustal anisot­ropies, and active magmatic processes beneath the Payún Matrú volcano. These findings suggest that both inherited structures and mantle-related thermal anomalies (SWAP) govern stress distribution and seismicity in the region.