An integrated crustal velocity field for the central Andes

Abstract

We present an integrated velocity field for the central Andes, derived from GPS observations collected between January 1993 and March 2001 that eliminates the velocity bias between the South America‐Nazca Plate Project (SNAPP) and central Andes GPS Project (CAP) velocity fields published by Norabuena et al. [1998] and Bevis et al. [1999]. The reference frame is realized by minimizing the motion of eight continuous GPS stations and one rover GPS station located in the stable core of the South American plate. The RMS horizontal motion of these stations is just 1.1 mm/yr. The amplitude of these residual motions is roughly compatible with expected levels of measurement error. In our new solution, five of the six SNAPP stations located just outside the orogenic belt are effectively stationary, and the velocities for adjacent CAP and SNAPP stations now agree at a level consistent with their formal uncertainties.