Mapping P-wave anisotropy of the Honshu arc from Japan Trench to the back-arc

Wang, Jian; Zhao, Dapeng

doi:10.1016/j.jseaes.2010.04.009

Cited by 41 publications

(46 citation statements)

References 68 publications

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“…These results suggest that the uppermost mantle deformation may belong to pure shear deformation due to the compression between Pamir and the western Tien Shan. A similar phenomenon has been observed in the European area (e.g., Hearn, 1999), northeast Japan (e.g., Wang and Zhao, 2010), and the Burma arc (e.g., Lei et al, 2014).…”

Section: The Western Tienshan and Pamirsupporting

confidence: 76%

Pn anisotropic tomography under the entire Tienshan orogenic belt

Zhou¹,

Lei²

2015

Journal of Asian Earth Sciences

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Section: The Western Tienshan and Pamirsupporting

confidence: 76%

Pn anisotropic tomography under the entire Tienshan orogenic belt

Zhou¹,

Lei²

2015

Journal of Asian Earth Sciences

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“…Based on the stress field and thermal structure of the upper mantle beneath NE Japan, several recent studies suggested that, while deformation throughout most of the mantle wedge is controlled by diffusion creep, the anisotropic zone of dislocation creep is limited to a thin layer with relatively high stress and low temperature located right above the subducting slab and another thin layer right beneath the island arc crust [ Katayama , 2009; Michibayashi et al , 2006, 2009]. Recent P wave anisotropic tomography shows that the anisotropy in the central portion of the mantle wedge is weaker than that in the uppermost mantle and atop the subducting slab [ Wang and Zhao , 2008, 2010; Eberhart‐Phillips and Reyners , 2009; Huang et al , 2011]. Thus the apparent small DTs in the mantle wedge may reflect an isotropic or weak anisotropic zone in the middle of the mantle wedge.…”

Section: Anisotropy In the Mantle Wedge And The Slabmentioning

confidence: 99%

Shear wave anisotropy in the crust, mantle wedge, and subducting Pacific slab under northeast Japan

Huang

Zhao

Wang

2011

Geochem. Geophys. Geosyst.

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[1] To study the anisotropic structure beneath northeast (NE) Japan, we made 4366 shear wave splitting measurements using high-quality seismograms of many earthquakes occurring in the crust and the subducting Pacific slab. Our results provide important new information on the S wave anisotropy in the upper crust, lower crust, mantle wedge, and subducting Pacific slab. In the upper crust, the anisotropy is mainly caused by the stress-aligned fluid-saturated microcracks. The measured delay times (DTs) increase to 0.10 s at 10-11 km depth; the fast velocity directions (FVDs) are parallel to either the tectonic stress or the strike of active faults. The maximum DTs for the low-frequency earthquakes near the Moho are 0.15-0.17 s, suggesting strong anisotropy at the base of the crust or in the uppermost mantle. The measurements for the intermediate-depth earthquakes in the Pacific slab show dominant E-W (trench-normal) FVDs in the back-arc area and N-S (trench-parallel) FVDs in the fore-arc area. The trench-normal FVDs in the back-arc area are caused by the corner flow in the mantle wedge as a result of the subduction of the Pacific plate. The maximum DTs for the slab earthquakes reach 0.30-0.32 s at 100 km depth, but only half of the total DTs are produced in the mantle wedge. The small DTs in the mantle wedge may result from an isotropic or weak anisotropic zone in the middle of the mantle wedge. In the fore arc, the dominant trench-parallel FVDs for the slab earthquakes are consistent with those for the upper crust earthquakes, and ∼80% of the total DTs can be accounted for by the anisotropy in the crust. In the subducting Pacific slab, the trench-parallel FVDs may reflect either the original fossil anisotropy in the Pacific plate when the plate was produced in the mid-ocean ridge or the preferred orientations of the crystals and cracks in the upper part of the subducting slab.Components: 8500 words, 15 figures.

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“…There are several examples of studies of subduction zones based on anisotropic tomography inversions [e.g., Eberhart‐Phillips and Henderson , ; Koulakov et al ., ; Rabbel et al ., ]. There are also several anisotropic tomographic models of various parts of Japan [e.g., Ishise and Oda , ; Huang et al ., ; Wang and Zhao , , ].…”

Section: Introductionmentioning

confidence: 99%

Anisotropic tomography of Hokkaido reveals delamination‐induced flow above a subducting slab

et al. 2015

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We present a new 3-D anisotropic seismic model for the crust and upper mantle beneath Hokkaido (Japan) based on tomographic inversion of P and S arrival times from a regional seismic database. The P model is parameterized with three parameters at each point that describe the azimuthal anisotropy; the S model is represented isotropically. The isotropic P and S velocity anomalies match nearly perfectly. In the crust, they show a prominent linear anomaly in central Hokkaido along the Kamuikotan and Hidaka Belts, which represents the area of eastward underthrusting of the Japan Block underneath the Kuril fore arc. We interpret the high-velocity anomaly beneath the Hidaka zone as being delaminated mafic crust and entrained mantle lithosphere, which developed due to crustal shortening in the collision zone. One of our vertical sections shows a very unusual configuration for a subduction zone: a low-velocity slab is overlain by a high-velocity body in the mantle wedge. We propose that the high-velocity delaminated material sinking along the slab surface prevents the escape of fluids and melts from the upper part of the slab, where they are generated due to phase transitions. As a result, a large portion of the fluids is entrained downward and lowers the seismic velocities in the slab. The azimuthal anisotropy in the crust clearly corresponds to the major tectonic units and delineates the major suture zones. In the mantle, the anisotropy has a fan-shaped configuration and most likely represents the deviating of flows starting in southern Hokkaido and splitting into three directions. The western and eastern flows proceed toward the two volcanic groups on Hokkaido, and they may carry with them additional material to trigger the characteristic caldera-forming eruptions in these groups.

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Mapping P-wave anisotropy of the Honshu arc from Japan Trench to the back-arc

Cited by 41 publications

References 68 publications

Pn anisotropic tomography under the entire Tienshan orogenic belt

Pn anisotropic tomography under the entire Tienshan orogenic belt

Shear wave anisotropy in the crust, mantle wedge, and subducting Pacific slab under northeast Japan

Anisotropic tomography of Hokkaido reveals delamination‐induced flow above a subducting slab

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