Tectonic Inversion of the SCS from 3-D Magnetization Vector Clustering: Evidence for Differential Rotation and Ridge Jump

The eastern and southwestern sub-basins of the South China Sea (SCS) display starkly contrasting magnetic lineation patterns, yet quantitative 3-D mapping of the subsurface magnetic architecture—essential for deciphering basin evolution—remains challenging due to the dominance of remanent magnetization. We introduce a joint workflow that integrates anomaly separation with Magnetization-Vector Clustering Inversion (MVCI) to resolve this challenge. A low-rank Hankel matrix filter first disentangles co-located seamount and stripe anomalies in the ocean basin; each component is then inverted using MVCI to recover 3-D magnetization intensity and direction without prior orientation constraints, while simultaneously deriving cluster statistics. Synthetic tests replicating the SCS crustal setting demonstrate that seamount-signal removal dramatically enhances inversion fidelity for both anomaly sources. Application to the SCS reveals two distinct vector clusters in the eastern sub-basin, with mean declinations indicating 10–24° counter-clockwise rotation relative to the southwestern sub-basin. Magnetization intensities are slightly stronger in the southwestern sub-basin, where NE-trending magnetic stripes exhibit narrow spacing, whereas the eastern sub-basin shows wider and more variable NE–W to E–W trending stripes. This study provides the first basin-scale quantification of along-strike magnetic heterogeneity, offering new quantitative constraints on late-stage seafloor spreading and the dynamic evolution of the SCS, while delivering a robust, transferable methodology for other remanence-dominated marginal seas.