Incoming Plate Variations Along The Northern Manila Trench: Implications For Seafloor Morphology And Seismicity

Incoming plate variations along the whole northern Manila trench are investigated by integrating 15 reflection and 3 refraction seismic lines across the trench. Based on the along-trench variation in sediment thickness, basement topography and crust thickness, the incoming crust is divided into three segments from north to south: segment A1-the rifted basin resulting from highly thinning of the continental curst, characterized by thick sediment, similar to 4-km-thin crust and basement low; segment A2-high basement relief region related to moderate thinning and magmatic modification, characterized by thin sediment, similar to 12-km-thick crust and basement highs; segment B-normal oceanic crust, characterized by flat and moderate thick sediment and similar to 6-km-thick crust. The segmentation of the incoming plate correlates well with the deformation pattern of the accretionary wedges and seismically active regions, implying that the preexisting heterogeneities inherited from the rifting process of the continental margin may have an important effect on carving seafloor morphology and seismicity at the precollision zone.