Heterogeneity within the subducting Pacific slab beneath the Izu-Bonin-Mariana arc: Evidence from tomography using 3D ray tracing inversion techniques

Meghan S. Miller*, A. Gorbatov, B. L.N. Kennett

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    66 Citations (Scopus)

    Abstract

    Distinct zones of seismic heterogeneity along the Izu-Bonin-Mariana arc have been investigated using complimenting regional bulk sound, shear wave speed, and P-wave tomographic images. The distribution of seismic anomalies and the inferred geometry of the subducting Pacific plate have been modelled in unprecedented detail using joint tomography and new P-wave model using a 3D inversion algorithm. The use of 3D ray tracing techniques and smaller cell parameterizations have greatly enhanced the resolution of gradients, therefore, the models show much more detail about the structure and physical properties of the subduction zone. The well-defined features from the multiple wave speed images are used to elucidate the distinct morphology change between slab beneath the Izu-Bonin (horizontal slab) and Mariana (vertical) arcs and the distribution of physical properties in the mantle and the subducting oceanic lithosphere. Changes in physical properties within the slab tear at the southern end of the Izu-Bonin arc, identified as a "gap or thinning" in the tomographic images, could be the result of the distortion of the Pacific plate as its shape transforms between near horizontal to near vertical, a decrease in the rigidity and strength of the lithosphere, the subduction of the Marcus-Necker Ridge, change in subduction velocity, or a combination of all these factors. Strong, slow anomalies exist both, in the mantle wedge, above and below the slab beneath the Izu-Bonin arc but are not present beneath the Mariana arc. At the junction between the Izu-Bonin and Mariana arcs it appears that the there are two separate pieces of the Pacific plate: the torn slab north of 26° N and a buckled near vertically dipping slab south of the tear. The transition between the two distinct slab morphologies coincides with the location of the Ogasawara Plateau and the trench.

    Original languageEnglish
    Pages (from-to)331-342
    Number of pages12
    JournalEarth and Planetary Science Letters
    Volume235
    Issue number1-2
    DOIs
    Publication statusPublished - 30 Jun 2005

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