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Upper Mantle Hydration Indicated by Decreased Shear Velocity Near the Southern Mariana Trench From Rayleigh Wave Tomography
Author(s) -
Zhu Gaohua,
Wiens Douglas A.,
Yang Hongfeng,
Lin Jian,
Xu Min,
You Qingyu
Publication year - 2021
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2021gl093309
Subject(s) - geology , forearc , seismology , mantle (geology) , trench , pacific plate , seismic tomography , low velocity zone , subduction , geophysics , tectonics , lithosphere , chemistry , organic chemistry , layer (electronics)
Reduction of seismic velocities has been employed to study the hydration of incoming plates and forearc mantle in recent years. However, few constraints have been obtained in the Southern Mariana Trench. We use an ocean bottom seismograph (OBS) deployment to conduct Rayleigh wave tomographic studies to derive the SV ‐ wave velocity structure near the Southern Mariana Trench. Measured group and phase velocities as a function of period are inverted to determine the SV ‐ wave velocity using a Bayesian Monte Carlo algorithm. The incoming Pacific Plate is characterized by low velocities (3.6–4.1 km/s) within the upper ∼25 km of the mantle near the trench, indicating extensive mantle hydration of the incoming plate in southern Mariana. The velocity reduction in the forearc mantle is not as large as in central Mariana, most likely indicating a lower forearc serpentinization in this region, which is consistent with the absence of serpentinite mud volcanoes.