Motion of the South Bismarck Plate, Papua New Guinea

The absolute motion of the South Bismarck Plate was first estimated by Tregoning et al. [1998] from three site velocities estimated from Global Positioning System (GPS) observations. We report an improved estimate of the Euler vector for this plate using site velocities derived from new GPS data which include the velocity of a site located ∼25 km from the pole of rotation. The GPS velocities of Madang, Witu, Jacquinot Bay and Finschafen can be modelled to within ∼3 mm/yr using a single pole of rotation located at 6.75°S, 147.98°E with a clockwise rotation rate of 8.11°/My. The known tectonic features and available geophysical data surrounding the South Bismarck Plate can also be explained by a rotation of the South Bismarck Plate about this pole.