Detachment-involved deformation in the Santa Bárbara system in NW Argentina revealed by seismicity and receiver functions

The central Andes show along-strike variations in crustal shortening that are reflected in foreland deformation styles. In NW Argentina, deformation in the Santa Bárbara system (SBS) likely involves reactivated Salta rift faults, but how these preexisting structures control regional deformation style remains unclear. This study analyzed present-day crustal deformation and the role of Salta rift structures using a new high-resolution earthquake catalog and receiver function images prepared using a new seismic array dataset. Results reveal a midcrustal detachment at ∼18 km depth along the brittle-ductile transition in the Salta-Jujuy high area, where Salta rift structures are absent. A shallower (∼8 km) detachment is observed to the north and east of this deep detachment, which is interpreted as the reactivated master detachment from the N-S−oriented Salta rift structures in this region. This detachment-involved deformation is not observed to the north of the SBS, likely due to the change in strike of Salta rift faults to a nonoptimal reactivation orientation in the current E-W compressional stress regime. Instead, diffuse midcrustal seismicity suggests low-magnitude distributed deformation, and concentrated shallow seismicity (<5 km depth) in the Eastern Cordillera indicates a westward shift of the primary deformation front north of the SBS.