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

Abstract

The central Andes show along-strike variations in crustal shortening that are reflectedin foreland deformation styles. In NW Argentina, deformation in the Santa Bárbara system(SBS) likely involves reactivated Salta rift faults, but how these preexisting structures controlregional deformation style remains unclear. This study analyzed present-day crustaldeformation and the role of Salta rift structures using a new high-resolution earthquakecatalog and receiver function images prepared using a new seismic array dataset. Resultsreveal a midcrustal detachment at ∼18 km depth along the brittle-ductile transition in theSalta-Jujuy high area, where Salta rift structures are absent. A shallower (∼8 km) detachmentis observed to the north and east of this deep detachment, which is interpreted asthe 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, likelydue to the change in strike of Salta rift faults to a nonoptimal reactivation orientation inthe current E-W compressional stress regime. Instead, diffuse midcrustal seismicity suggestslow-magnitude distributed deformation, and concentrated shallow seismicity (<5 kmdepth) in the Eastern Cordillera indicates a westward shift of the primary deformationfront north of the SBS.