The effect of subducting oceanic plateau on the bending and hydration processes in the southern Mariana trench

The subduction of oceanic plateaus is a global phenomenon that reshapes the tectonic configuration of subduction systems and plays a crucial role in water cycling and volatile fluxes. While previous studies have primarily focused on the processes occurring after plateaus into subduction zones, but the effects of subducting oceanic plateaus on bending and hydration before subduction remain unclear. Using wide-angle seismic data perpendicular to the trench, we investigated these processes as the Caroline Plateau approaches the trench. The P-wave velocity structure shows a gradual increase in crustal thickness from ~7.5 km beneath the trench and outer trench slope, 9.0–12.0 km in the outer rise region, to 16.0–17.0 km beneath the plateau, indicating that the Caroline oceanic plateau is approaching the trench. Seismic velocities near trench axis are lower than those in other subduction zones and at Challenger Deep to the east, where the trench is far from the oceanic plateau. These low seismic velocities, combined with a narrower array of normal faults, suggest that the participation of the oceanic plateau in the subduction process reduces the width of bending fault zone parallel to the trench, while increasing fracturing, serpentinization in the lithosphere ahead of the plateau. Along the trench, the juxtaposed subduction of the oceanic plateau and oceanic crust influences the tectonic configuration of the overriding plate, highlighting the impact of incoming oceanic plateau on subduction dynamics.