Crustal motion north and south of the Arica deflection: Comparing recent geodetic results from the central Andes

An intercomparison of recent velocity solutions for the Global Positioning System (GPS) networks constructed by the South American-Nazca Plate Project (SNAPP), based in Bolivia and Peru, and our Central Andes GPS Project (CAP), based in Chile and Argentina, indicates a velocity discontinuity of order 10 mm/yr near the boundary between these networks. We suggest that this velocity jump manifests measurement bias in the SNAPP velocity field. Our results indicate that no major slip partioning occurs within the forearc of northern Chile in response to the obliquity of subduction but that Nazca-South America plate convergence is partitioned between the forearc and the backarc regions. The present rate of shortening across the southern part of the sub-Andean belt in Argentina is 8.9 +/- 1.6 mm/yr.