The 3D lithospheric structure of China Seas and adjacent areas: Combining geoid, gravity, and topography data

Abstract

The convergence of the Pacific, Eurasian, Philippine Sea, and Caroline Plates makes the China Seas and adjacent areas a natural laboratory for studying lithospheric evolution at ocean-continent transitions. We present a novel three-dimensional (3D) lithospheric model through an advanced joint inversion framework integrating multi-geophysical datasets (geoid, free air gravity anomaly, topography, and seismic Moho constraints). This study features three key advances: (1) A zonal parameterization scheme achieving higher lateral resolution than conventional models, delineating 15 tectonic units (10 km grid) with distinct thermal and density properties; (2) Integration of seismic Moho constraints, depth-dependent crustal/sedimentary densities, and thermally modulated mantle densities to enable comprehensive lithospheric characterization; (3) Key lithospheric transects reveal: (i) Progressive lithospheric thinning from cratonic basins (Ordos: 160 ± 5 km; Sichuan: 155 ± 7 km) to active margins (Okinawa Trough: 80 ± 10 km), with LAB uplift amplitudes (Bohai Bay: 50 ± 8 km; South China Block: 35 ± 6 km) correlating with Pacific slab rollback; (ii) Seafloor spreading in the South China Sea has resulted in LAB uplift of 40 ± 5 km, associated with mantle upwelling consistent with previous geodynamic modeling. These findings redefine the 3D lithospheric framework of the study area, illustrating the interplay between plate boundary forces, mantle dynamics, and lithospheric deformation across ocean-continent transitions. Although our results don’t change fundamentally the overall lithospheric image of the area, our results provide better constraints for advancing geodynamic models and offer key insights into non-isostatic subduction dynamics within complex plate interactions.