• Lau Basin;
  • plate kinematics;
  • microplate;
  • seafloor spreading;
  • geodetic vectors

[1] We present revised compilations of bathymetry, magnetization, acoustic imagery, and seismicity data for the Lau Basin and surrounds. We interpret these data to more precisely locate the plate boundaries in the region and to derive a three-plate kinematic model for the opening of the Lau Basin during the Brunhes Chron. Our tectonic model includes the Niuafo'ou microplate, which is separated from the Australian Plate along the Peggy Ridge-Lau Extensional Transform Zone-Central Lau Spreading Center and from the Tongan Plate along the newly discovered Fonualei Rift and Spreading Center. Our model shows that Australia-Tonga plate motion between 15.5°S and 19°S is partitioned across the microplate, and it resolves the former apparent conflict between geodetic versus seafloor spreading velocities. Regionally, this implies that the angular rate of opening of the Lau Basin has been faster than that of the Havre Trough to the south and that the rapid current rates of Pacific subduction at the Tonga Trench (∼240 mm/yr at 16°S) have been sustained for at least 0.78 m.y.