Radial and Azimuthal Anisotropy Tomography of the NE Japan Subduction Zone: Implications for the Pacific Slab and Mantle Wedge Dynamics

Ishise, Motoko; Kawakatsu, Hitoshi; Morishige, Manabu; Shiomi, Katsuhiko

doi:10.1029/2018gl077436

Cited by 14 publications

(15 citation statements)

References 28 publications

(42 reference statements)

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“…The convergence of the ILM and ELM has caused eastward asthenospheric flow (Yin & Taylor, 2011), which may induce the E‐W trending SWB features. Since the deformation pattern in the mantle wedge is almost horizontal if there is no small‐scale convection (Ishise et al., 2018), a positive RAN should be observed, which is different from our results. Therefore, we suggest that small‐scale convection occurs above the ILM (L1 and H1’ in Figures 3 and 4).…”

Section: Discussioncontrasting

confidence: 99%

“…On the basis of the above discussions, the LVZ above the ILM can be considered as a “mantle wedge” (L1 in Figure 4a). Results of both numerical simulation and RAN tomography have illustrated the small‐scale convection occurring in the mantle wedge (Ishise et al., 2018; Liu & Zhao, 2017), in which the fast polarization directions in the forearc inferred from SWB measurements are perpendicular to the subduction direction (Huang et al., 2011), and negative RAN prevails in the mantle wedge (Liu & Zhao, 2017). The convergence of the ILM and ELM has caused eastward asthenospheric flow (Yin & Taylor, 2011), which may induce the E‐W trending SWB features.…”

Section: Discussionmentioning

confidence: 99%

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Upper Mantle Heterogeneity and Radial Anisotropy Beneath the Western Tibetan Plateau

Zhang

Zhao

et al. 2021

Tectonics

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It is generally considered that the tectonic evolution of the Tibetan Plateau is influenced by continental collision (e.g., Yin & Harrison, 2000), but many fundamental issues are still not resolved. For example, what happens in the advancing Indian lithospheric mantle (ILM), and what are the responses of the Eurasian lithospheric mantle (ELM)? Zhou and Murphy (2005) suggested that the ILM has subducted beneath the whole Tibet, whereas Kind et al. (2002) detected the ELM in northern Tibet. In recent years, some studies have revealed significant east-west variations of the northward advancing ILM (e.g., J. T. Li & Song, 2018; X. F. Liang et al., 2016). A subvertical high-velocity zone has been revealed at depths of 100-400 km by seismic tomography (Tilmann et al., 2003), and it was interpreted as a downwelling lithosphere in eastern Abstract P-wave radial anisotropy (RAN) tomography of the upper mantle beneath the western Tibetan Plateau is determined using teleseismic arrival time data recorded at 71 temporal seismic stations of the ANTILOPE-I and Y2 arrays, which reveals a complex deformation pattern in the upper mantle. A high-velocity anomaly with prominent positive RAN is visible to the south of 31°N, which may reflect the underthrusting Indian lithospheric mantle (ILM). Further north, another high-velocity zone appears at depths >200 km, which is possibly related to the foundering ILM, or the northward advancing ILM affected by previously attached Tethyan oceanic slab. Considering the continuity of the high-velocity zones and similarity of the RAN anomalies, we suggest that there is no slab tearing or breakoff at present beneath western Tibet. To the north of 31°N, E-W trending variations of velocity and RAN at shallow depths (<150 km) suggest that small-scale convection occurs between 79°E and 81°E, whereas the residue of the Eurasian lithospheric mantle is located in the eastern side. We deem that the formation of the Ya-Re Rift and Puran Graben was caused by variations of the lithospheric thickness instead of slab tearing or asthenospheric upwelling, considering locations of the rift and the graben and our present results. Plain Language Summary Our study region, the Tibetan Plateau, is a hot and ideal region to study the mechanisms of the convergence between continental plates. It is generally considered that the Tibetan Plateau is a product of convergence between the Indian and Eurasian plates, but some fundamental issues are still not resolved. For example, what happens in the northward advancing Indian lithospheric mantle (ILM), and what are the responses of the Eurasian lithospheric mantle (ELM)? Because of the extremely hard environment in the western Tibetan Plateau, seismic tomography is an effective way to illuminate the underground structure by processing earthquake waveforms recorded at seismograph stations. Although the interpretations of velocity anomalies are consistent, the anisotropy features result in different conclusions. Our results reveal both horizontal and vertical variations in the ...

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Section: Discussioncontrasting

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Upper Mantle Heterogeneity and Radial Anisotropy Beneath the Western Tibetan Plateau

Zhang

Zhao

et al. 2021

Tectonics

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“…On the other hand, Ishise et al (2018) also conduct a P-wave radial anisotropy study of NE Japan and find negative radial anisotropy (V PH < V PV ) in the mantle wedge and positive radial anisotropy (V PH > V PV ) in the subducting slab. Instead of invoking different olivine types, Ishise et al (2018) explain their results by small-scale convection in the mantle wedge assuming an A-type olivine fabric. Numerical simulations by Morishige and Honda (2011) indicated steep downflows and gentle upflows, which would produce strong negative radial anisotropy given an A-type olivine fabric in the mantle wedge.…”

Section: Discussionmentioning

confidence: 99%

“…On the other hand, Ishise et al. (2018) also conduct a P‐wave radial anisotropy study of NE Japan and find negative radial anisotropy ( V PH < V PV ) in the mantle wedge and positive radial anisotropy ( V PH > V PV ) in the subducting slab. Instead of invoking different olivine types, Ishise et al.…”

Section: Discussionmentioning

confidence: 99%

Radial Anisotropy in East Asia From Multimode Surface Wave Tomography

et al. 2021

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The field of seismic tomography has advanced to the point that researchers have been able to determine the isotropic velocity structure of the Earth on a global and regional scale with increasing consistency despite varying methodologies and data sets. Tomographic studies have succeeded in imaging and interpreting large-scale structures such as subducting slabs and upwelling plumes across the globe (e.g.,

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“…Comparing the previous model of the top of the PHS slab (Figure S4b), the upper surface of the PHS slab is clearly shallower under the Tokyo Bay and the Boso Peninsula than the previous model. However, since only one aspect of anisotropy, azimuthal anisotropy, has been investigated in this study, it will be necessary in the future to consider vertical anisotropy (e.g., Ishise et al., 2018) and the structure of the subduction zone, including the slab structure.…”

Section: Discussionmentioning

confidence: 99%

Improved 3‐D P Wave Azimuthal Anisotropy Structure Beneath the Tokyo Metropolitan Area, Japan: New Interpretations of the Dual Subduction System Revealed by Seismic Anisotropy

et al. 2021

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The Kanto region of Japan, including the Tokyo metropolitan area, is located on the thick sediment of the Kanto Basin in the Okhotsk (OKH) plate. The tectonics of the area are dominated by the dual subduction of the Philippine Sea (PHS) plate and the Pacific (PAC) plate (Figure 1). As a result, the Kanto region has been severely damaged by M8-class earthquakes, which occur along the plate interfaces, as well as many M7class earthquakes within the subducting slabs (in Japanese, 2004, available at http://www.bousai.go.jp/jishin/syuto/taisaku_wg/pdf/syuto_wg_siryo04.pdf). Many studies have investigated seismic activity, seismic

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Radial and Azimuthal Anisotropy Tomography of the NE Japan Subduction Zone: Implications for the Pacific Slab and Mantle Wedge Dynamics

Cited by 14 publications

References 28 publications

Upper Mantle Heterogeneity and Radial Anisotropy Beneath the Western Tibetan Plateau

Upper Mantle Heterogeneity and Radial Anisotropy Beneath the Western Tibetan Plateau

Radial Anisotropy in East Asia From Multimode Surface Wave Tomography

Improved 3‐D P Wave Azimuthal Anisotropy Structure Beneath the Tokyo Metropolitan Area, Japan: New Interpretations of the Dual Subduction System Revealed by Seismic Anisotropy

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