Revealing Subsurface Complexity of the West Philippine Basin by a Multi-Method Magnetic Analysis

Understanding the tectonic evolution of oceanic basins is critical for reconstructing the geological history of the Earth. The West Philippine Basin (WPB), located at the intersection of major tectonic plates in the Western Pacific, presents a complex geological environment with unresolved questions regarding features like the Gagua Ridge and the extent of Cretaceous oceanic crust. We propose a novel data processing approach that integrates singular spectrum analysis and normalized source strength to effectively extract residual and regional magnetic anomalies. By applying three-dimensional oblique magnetization inversion to the extracted regional anomalies, we revealed the magnetic structure of the WPB. Our results suggest that the Gagua Ridge exhibits characteristics of a volcanic arc in deep-source magnetization, supporting its formation as an immature intra-oceanic arc linked to Pacific Plate subduction. Additionally, we inferred the possible extent of Cretaceous oceanic crust within the Huatung Basin and identified a shallow demagnetization zone in the southeastern Gagua Ridge, attributed to South China Sea Plate subduction. These findings enable the construction of a tectonic model that elucidates the evolution of the WPB, offering new insights into the dynamic mechanisms of tectonic subduction systems in the western Pacific, and also provide a valuable tool for studying complex tectonic regions worldwide.