On January 18, 2021, a blind mid-crustal Mw ~6.4 earthquake occured near San Juán, Argentina. The observation of associated ground deformation with InSAR is hidden by strong tropospheric signals. We properly correct the data and reconstruct the deformation field through InSAR timeseries approach. We show it is possible to retrieve such signal with sufficient quality to invert the fault parameters. The ground deformation can be explained by uniform slip of a single NW dipping fault plane at a depth of 19km, and the geometry of such fault supports the reactivation of inherited structures on top of the Cuyania Terrane, insinuating a direct connection and strain transfer to the active east-vergent Precordillera front.