The Nazca South America Euler vector and its rate of change

We present velocities relative to the South American plate for five GPS stations on the Nazca plate and use these measurements to estimate the modem Euler vector. We find a pole at 55.8degreesN, 92.5degreesW with a rotation rate of 0.60degrees/Myr. Because the GPS station at Easter Island appears to be moving at approximately 6.6 mm/yr relative to the other Nazca stations, we repeat our analysis with this station excluded from the inversion to obtain a second and preferred result (called CAP10) with a pole at 61.0degreesN, 94.4degreesW and a rate of 0.57degrees/Myr. We compare these results with published finite rotation vectors and infer that during the past 10-20 Myrs, the Nazca-South America rotation rate has decelerated by 0.04degrees-0.06degrees/Myr(2). (C) 2003 Elsevier Science Ltd. All rights reserved.