Segmentation of the Manila subduction zone and slab tearing beneath the Philippine mobile belt

The Philippine Fault Zone (PFZ) is a key tectonic structure associated with crustal deformation and earthquakes throughout the Philippine Archipelago. Understanding its structures and related mechanisms can significantly mitigate seismic hazards. However, the complete structure of the PFZ, particularly its northwest termination in west Luzon, remains ambiguous. Based on newly acquired multichannel seismic reflection profiles and high-resolution bathymetric data, we have identified four roughly NW-SE trending fault zones off west Luzon, interpreted as branch faults of the northwestward prolongation of the inland PFZ. The southernmost branch could be the offshore extension of the principal NW-SE trending PFZ in central Luzon, terminating at the Manila Trench near ∼ 119°E and ∼ 17.5°N and segmenting the Manila Trench. A new transform fault could be formed to connect the northern and the southern Manila Trench segments. However, the trend of the Manila Trench has changed ∼ 35° counterclockwise from north to south. Coinciding with the NW-SE trending PFZ in central Luzon, the Manila subducting slab beneath central Luzon has been torn, as revealed by seismic tomography and seismicity. The northern subducted slab dips 40° eastward, while the southern slab dips 80° eastward. The segmentation of the Manila subduction zone along the NW-SE trending principal PFZ could be due to the southeastward collision of the Palawan microcontinental block against the Philippine mobile belt near Mindoro and the northwestward docking of the Benham Rise. The segmentation of the Manila subduction zone and slab tearing could dominate regional kinematics and crustal deformation.