Crustal structures of Southmost Mariana Trench revealed by wide-angle seismic profile TS01

Mariana Trench of Western Pacific Subduction System possesses complicated tectonic settings and vigorous subduction dynamics. Wide-angle seismic profile TS01 traverses the Caroline Plateau, Southmost Mariana Trench and Forearc. We obtained a velocity structure of TS01 via forward modeling based on reflection and refraction phases recorded by 9 OBSs. Furthermore, Bouguer gravity anomaly was calculated based on satellite gravity and multi-beam bathymetric data, and is used to analyze the variations of crustal thickness. Gravity modeling was further conducted to constrain the crustal and uppermost mantle structure. Our velocity model shows a wedge-shaped forearc crust, and relatively low velocities at inner trench slope, which may have arisen from subduction erosion. The velocities of subducting crust range from 4. 0 to 7. 2 km . s(-1). The crustal thickness of the subducting plate is approximately 12 similar to 13 km, thicker than typical oceanic crust but thinner than many oceanic plateaus. Three interfaces (interfaces between upper and lower plates, mid-crustal interface and Moho of subducting slab) are constrained by reflection phases of OBSs. Gravity modeling shows a low-density area beneath the trench, indicating serpentinization in the uppermost mantle of the downgoing plate. Our results lay a solid foundation for revealing the subduction dynamics near an oceanic plateau.