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西菲律宾海盆地分为主盆地、西北次盆地和南次盆地。这些盆地经历过不同的构造历史。主盆地中保存有磁异常条带17—21(?),并表明盆地是由两翼型海底扩张形成的。目前已仃熄的扩张中心位于伴有北西走向的中央盆地断层的崎岖地形带内。中央盆地断层的地貌主要是扩张后的构造作用造成的。主盆地的磁异常图型并没有延入南次盆地或西北次盆地。几何轮廓表明南次盆地并不是主盆地南翼的一部分。南次盆地可能是恰好在海岭突变为主盆地扩张轴之前形成的。或者,在南次盆地中可能较浅的地壳深度或许表明南次盆地比主盆地年轻,并不同于主盆地而形成的。西北次盆地是作为主盆地的一部分形成的,其主要地形走向与主盆地的垂直。这种地形上的差异,以及西北次盆地中热流较高,深度较浅的现象,标志西北次盆地遭受过未波及主盆地的变形事件。该变形事件也许与中第三纪时期沿东吕宋边缘的俯冲作用有关。加瓜海岭是沿西北次盆地西缘的隆起洋壳碎片,它大概是那次事件造成的。
The West Philippine Sea Basin is divided into the main basin, the Northwest sub-basin and the South basin. These basins have undergone different tectonic histories. The main basin contains magnetic anomaly bands 17-21 (?), Indicating that the basin was formed by the divergence of two airfoils. The now-expansive expansion center is located in the rugged terrain with a central NW north-west strike. The faulting of the central basin is mainly caused by the tectonic expansion. The main anomaly pattern did not extend to the South Sub-basin or the Northwest Sub-basin. Geometrical profiles indicate that the southern sub-basin is not part of the southern wing of the main basin. The South Sub-basin may have formed just before the ridge changed into the main axis of expansion. Alternatively, the shallow crustal depths in the South sub-basin may indicate that the South sub-basin was younger than the main basin and formed distinctly from the main basin. The Northwest Sub-basin was formed as part of the main basin, with its main terrain heading vertically to the main basin. This difference in topography and the high heat flux and shallow depth in the Northwest sub-basin indicate that the Northwest sub-basin suffered deformation events that did not reach the main basin. This deformation event may be related to the subduction of the eastern margin of eastern Luzon in the mid-Tertiary period. The Gaba Ridge is a patch of uplifted oceanic crust along the western margin of the Northwest Sub-basin, presumably caused by that event.