Space-geodetic estimation of the Nazca-South America Euler vector

GPS data from four sites in the Nazca Plate (Easter Island, Galapagos, Robi nson Crusoe and San Felix Islands) and from five sites in the stable core o f the South American Plate enabled us to estimate the Euler vector of the N azca Plate with respect to South America. The observed velocities of Easter Island (6.6 cm/yr at 102.3 degrees), Galapagos (5.1 cm/yr at 90.0 degrees) , Robinson Crusoe (6.6 cm/yr at 80.1 degrees) and San Felix (6.0 cm/yr at 8 2.1 degrees) are significantly slower than the global plate model NUVEL-1A velocites for those four sites. Our estimated Euler pole is located at 48.8 degrees N, 91.7 degrees W with a rate of 0.59 degrees/m.y. The NUVEL-1A an d earlier space-geodetic studies give rotation rates that are 20% faster. ( C) 1999 Elsevier Science B.V. All rights reserved.