Deep subducting slab reconstruction and its geometry, kinematics: a case study for the Tonga-kermadec slab from tomography

The Tonga-Kermadec subdction zone between the southwest Pacific Plate and the Australian Plate is one of the key regions to the Geodynamics research. In this paper, in order to map the 3-D geometries of subducting slabs, the MIT-P08 seismic tomography dataset have been add to the GOCAD software by integrating with tectonic boundaries, earthquakes and coastlines. The tomography shows there are three anomalously fast regions in the mantle beneath the Tonga-Fiji area. The Tonga-kermadec slab have subducted into the mantle transition zone and penetrated into the lower mantle. The maximum subducted depth is about 1600 km. 3-D structural model reveals the Tonga-kemadec slab is faulting and folding at 600~800 km depth. After the subducting slab is unfolding and restoration, measuring its maximum subducted displacement nearly 2600 km. The results indicate that the Tonga-kemadec slab subducted before 30 Ma at least with the average rates of 68~104 mm/a. Reconstruction and recovery of the 3-D slab can reveal the detailed geometry and the kinematics of subducting slab, which is providing the constraints to the deep earthquakes, the deep earth processes and dynamic mechanism.