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1 Institute of Geological and Nuclear Science, Lower Hutt 6315, New Zealand
2 Department of Earth and Environmental Science, Rensselaer Polytechnic Institute, 110 8th Street, Troy, New York 12180, USA
3 Institute of Geological and Nuclear Science, Lower Hutt 6315, New Zealand
Using global positioning system velocities from convergent plate boundaries in Papua New Guinea, New Zealand, Tonga, Vanuatu, and the Marianas, we note a spatial correlation between rapid tectonic block rotations and the transition from subduction to collision. We present a mechanism for the block rotations, in which the change from collision of a buoyant indentor to normal subduction exerts a torque on the upper-plate microplate. This work improves our understanding of the causes of rapid vertical axis rotations, often observed in paleomagnetic studies. We also show how collision-induced rotations may lead to backarc rifting.
Key Words: GPS global positioning system collision subduction microplate rotation backarc rifting tectonics
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