Deformations control for the Chilean part of the SIRGAS 2000 frame

With the adoption of the Geocentric Reference System for the Americas (SIRGAS), the determination of temporal variations and deformations in its frame are a necessary task. These tasks are fundamental in order to maintain the consistency of the frame with respect to the definition of SIRGAS, especially in the Chilean deformation area, where the variations are larger compared with the rest of the plate due to the convergence between the South American and Nazca plates. 21 permanent GPS stations was used. 14 of them are regional stations of the International GNSS Service (IGS), and 7 permanent GPS stations are from different regional networks. 10 of these 21 stations arc located in the Chilean Andes were used to study the kinematic effects in this area. Some of them are also SIRGAS stations. Five years of GPS observations from 2000 to 2004 were selected in order to have a sufficient time period with enough coverage for the considered stations. Daily solutions were generated with the Bernese GPS Software 5.0 using IGS precise ephemeris, clocks and ERP. The normal equations were then accumulated and solved in a final combination where the coordinates and velocities of selected stations are weighted for the datum definition compatible with ITRF2000. The estimated velocities of the north Chilean Andes regions are ~26-30 ± 2mm/yr, decreasing up to ~16-25 ± 2mm/yr and for the south Chilean Andes the estimated velocities are ~9-12 ± 2mm/yr. For the stable part of the continent the estimated velocities are ~8-12 ± 2mm/yr. The final results are discussed and compared with the NUVEL-1A and SIRGAS velocity models (SIRGAS-VM).