Structure and dynamics of the Tonga subduction zone: New insight from P-wave anisotropic tomography - Université de Bretagne Occidentale Access content directly
Journal Articles Earth and Planetary Science Letters Year : 2022

Structure and dynamics of the Tonga subduction zone: New insight from P-wave anisotropic tomography

Abstract

The Tonga-Lau-Fiji region is important to study plate-plume and subduction-ridge interactions, but its deep mantle structure is still not very clear. Here we present high-resolution tomography of 3-D P-wave azimuthal anisotropy down to 400 km depth of the Tonga subduction zone derived from arrival-time data of local earthquakes recorded at seafloor and land seismometers. The subducting Tong slab is imaged as high-velocity anomalies at depths of 100-400 km, whereas large-scale low-velocity anomalies down to 400 km depth are revealed in the mantle wedge beneath the backarc basin and volcanic arc. Trenchparallel anisotropy beneath the Lau Basin extends southwards to ∼140 km depth at ∼20.5 • S, representing the extent of both southward flow of the Samoan plume and toroidal flow by the slab rollback. At depths of 140-400 km, the Lau Basin and Fiji Plateau mainly exhibit plate-parallel fast-velocity directions (FVDs) north of ∼20.5 • S, indicating strong corner flow in the mantle wedge driven by the slab subduction and dehydration. The Tonga slab exhibits trench-parallel FVDs at depths of <200 km, reflecting fossil fabric formed during the plate spreading stage, whereas, at greater depths, the slab mainly exhibits trenchnormal FVDs, which may reflect complicated deformations within the slab. These results suggest that the Samoan plume has a significant impact on the Tonga-Lau-Fiji region, leading to variations in the scale and depth extent of mantle flows.
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Dates and versions

hal-04157953 , version 1 (10-07-2023)

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Zhiteng Yu, Dapeng Zhao, Jiabiao Li. Structure and dynamics of the Tonga subduction zone: New insight from P-wave anisotropic tomography. Earth and Planetary Science Letters, 2022, 598, ⟨10.1016/j.epsl.2022.117844⟩. ⟨hal-04157953⟩
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