Back-Arc Tectonics and Plate Reconstruction of the Philippine Sea-South China Sea Region Since the Eocene

Insight into the evolution of Philippine Sea-South China Sea (SCS) plate motions helps reveal the driving mechanisms of the long-term tectonic complexity in Southeast Asia. Here, based on the integration of the most recent geological and seismic data, we present a new plate reconstruction model for this region characterized by back-arc extension and subduction since the Eocene. We suggest that the western boundary of the Philippine Sea Plate was a constant sinistral strike-slip fault at 55–22 Ma with a clockwise self-rotation. The connection between the SCS and Shikoku Ridges possibly initiates at 30 Ma, when their spreading times overlapped indicating an affinitive origin and magma source. Regional-scale geodynamic simulations interfaced with our reconstructed plate motion indicate that the seismic high-velocity body under the SCS is likely to be the leading edge of the Pacific Slab.