RELATIVE MOTIONS OF THE AUSTRALIAN, PACIFIC AND ANTARCTIC PLATES ESTIMATED BY THE GLOBAL POSITIONING SYSTEM

GPS measurements spanning similar to 3 years have been used to determi ne velocities for 7 sites on the Australian, Pacific and Antarctic pla tes. The site velocities agree with both plate model predictions and o ther space geodetic techniques. We find no evidence for internal defor mation of the interior of the Australian plate. Wellington, New Zealan d, located in the Australian-Pacific plate boundary zone, moves 20+/-5 mm/yr west-southwest relative to the Australian plate. Its velocity l ies midway between the predicted velocities of the two plates. Relativ e Euler vectors for the Australia-Antarctica and Pacific-Antarctica pl ates agree within one standard deviation with the NUVEL-1A predictions .