Motion of the South Bismarck Plate, Papua New Guinea

The absolute motion of the South Bismarck Plate was first estimated by Treg oning et al. [1998] from three-site velocities estimated from Global Positi oning System (GPS) observations. We report an improved estimate of the Eule r vector for this plate using site velocities derived from new GPS data whi ch include the velocity of a site located similar to 25 km from the pole of rotation. The GPS velocities of Madang, Witu, Jacquinot Bay and Finschafen can be modelled to within,similar to 3 mm/yr using a single pole of rotati on located at 6.75 degrees S, 147.98 degrees E with a clockwise rotation ra te of 8.11 degrees/My. The known tectonic features and available geophysica l data surrounding the South Bismarck Plate can also be explained by a rota tion of the South Bismarck Plate about this pole.