Upper Mantle Hydration Indicated by Decreased Shear Velocity Near the Southern Mariana Trench From Rayleigh Wave Tomography

Reduction of seismic velocities has been employed to study the hydration incoming plates and forearc mantle in recent years. However, few constraints have obtained Southern Mariana Trench. We use an ocean bottom seismograph (OBS) deployment conduct Rayleigh wave tomographic studies derive SV-wave velocity structure near Measured group phase as a function period are inverted determine using Bayesian Monte Carlo algorithm. The Pacific Plate is characterized by low (3.6–4.1 km/s) within upper ?25 km trench, indicating extensive plate southern Mariana. reduction not large central Mariana, most likely lower serpentinization this region, which consistent with absence serpentinite mud volcanoes.