TY - JOUR
T1 - Upper Mantle Structure Beneath Mariana
T2 - Insights From Rayleigh-Wave Anisotropic Tomography
AU - Qiao, Qingyu
AU - Liu, Xin
AU - Zhao, Dapeng
AU - Li, Sanzhong
AU - Zhao, Shujuan
AU - Zhao, Long
AU - Wang, Xiao
N1 - Funding Information:
The authors are very grateful to Prof. Maureen Long (the Editor), Prof. Karen Fischer, and two anonymous reviewers for their helpful review comments and suggestions, which have improved this article. This work was supported by grants from the National Natural Science Foundation of China (41602207, 41972211) to X. Liu and a grant from Japan Society for the Promotion of Science (19H01996) to D. Zhao.
Publisher Copyright:
© 2021. The Authors.
PY - 2021/11
Y1 - 2021/11
N2 - We determine Rayleigh-wave phase-velocity azimuthal anisotropy tomography beneath Mariana using a large number of high-quality amplitude and phase data of teleseismic fundamental mode Rayleigh waves at periods of 25–130 s. The obtained phase-velocity model is then inverted for a 3D azimuthal anisotropic shear-wave velocity (Vs) model down to ∼300 km depth. The old (∼150 Ma) Pacific oceanic lithosphere near the Mariana trench is imaged as a clear high-Vs zone with a thickness of ∼100 km, whereas obvious low-Vs anomalies exist in the mantle wedge and in the asthenosphere beneath the incoming plate. The Pacific oceanic lithosphere near the Mariana trench mainly exhibits a fast-velocity direction (FVD) of NW-SE normal to seafloor isochrons, which may reflect frozen-in lattice-preferred orientation formed at the mid-ocean ridge, whereas the dominant FVD in the subducting Pacific slab at depths >∼100 km is parallel to the Mariana trench, probably reflecting subduction-related structural deformation in the slab. Significant trench-normal FVDs exist in the mantle wedge at depths <∼100 km, whereas the deeper portion of the mantle wedge mainly exhibits trench-parallel FVDs, which may indicate a flow pattern in the mantle wedge due to the slab deep subduction and dehydration.
AB - We determine Rayleigh-wave phase-velocity azimuthal anisotropy tomography beneath Mariana using a large number of high-quality amplitude and phase data of teleseismic fundamental mode Rayleigh waves at periods of 25–130 s. The obtained phase-velocity model is then inverted for a 3D azimuthal anisotropic shear-wave velocity (Vs) model down to ∼300 km depth. The old (∼150 Ma) Pacific oceanic lithosphere near the Mariana trench is imaged as a clear high-Vs zone with a thickness of ∼100 km, whereas obvious low-Vs anomalies exist in the mantle wedge and in the asthenosphere beneath the incoming plate. The Pacific oceanic lithosphere near the Mariana trench mainly exhibits a fast-velocity direction (FVD) of NW-SE normal to seafloor isochrons, which may reflect frozen-in lattice-preferred orientation formed at the mid-ocean ridge, whereas the dominant FVD in the subducting Pacific slab at depths >∼100 km is parallel to the Mariana trench, probably reflecting subduction-related structural deformation in the slab. Significant trench-normal FVDs exist in the mantle wedge at depths <∼100 km, whereas the deeper portion of the mantle wedge mainly exhibits trench-parallel FVDs, which may indicate a flow pattern in the mantle wedge due to the slab deep subduction and dehydration.
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U2 - 10.1029/2021GC009902
DO - 10.1029/2021GC009902
M3 - Article
AN - SCOPUS:85119889919
SN - 1525-2027
VL - 22
JO - Geochemistry, Geophysics, Geosystems
JF - Geochemistry, Geophysics, Geosystems
IS - 11
M1 - e2021GC009902
ER -