Shear wave splitting from local events beneath the Ryukyu arc: Trench-parallel anisotropy in the mantle wedge

Long, Maureen D.; Hilst, R. D. van der

doi:10.1016/j.pepi.2006.01.003

Cited by 141 publications

(160 citation statements)

References 76 publications

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“…In general, the observed fast polarizations are oriented mainly parallel to the trench, which is consistent with the results obtained by F-net array in the Ryukyu arc (Long and van der Hilst, 2006). Trench-parallel polarization at the forearc has been observed in northeastern Japan (Okada et al, 1995), New Zealand (Marson-Pidgeon et al, 1999;Audoine et al, 2000), and Tonga (Smith et al, 2001).…”

Section: Discussionsupporting

confidence: 90%

Shear-wave anisotropy beneath the Ryukyu arc

Nakamura

Yamamoto

2009

Earth Planet Sp

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We have investigated regional shear-wave splitting beneath the Ryukyu arc in order to clarify the mantle flow beneath the Ryukyu arc and compare it with the extension of the Okinawa Trough. The splitting of regional shear waves (direct S) in the central and southern Ryukyu arc regions was analyzed in terms of fast-polarization direction and delay time using data from 11 short-period stations and two broadband seismic stations. The events occurred at depths ranging between 45 and 217 km, and the magnitude of the events ranged from 2.8 to 5.2. In general, the orientations of fast polarization were found to parallel to the strike of the Ryukyu Trench, with average delay times of 0.25-0.56 s. Specifically, the orientation of fast polarization was parallel to the direction of the extension in the south Ryukyu arc, suggesting that the direction of mantle flow is parallel to the extension in the south Okinawa Trough. However, the orientation of fast polarization was oblique to the direction of extension in the central Ryukyu arc, indicating that the mantle flow beneath the central Ryukyu arc is not parallel to the extension of the central Okinawa Trough. Based on these results, we suggest that the difference between the direction of the mantle flow and that of the lithosphere extension induces extensional strain with a simple shear component, which in turn causes oblique rifting in the central Okinawa Trough.

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Section: Discussionsupporting

confidence: 90%

Shear-wave anisotropy beneath the Ryukyu arc

Nakamura

Yamamoto

2009

Earth Planet Sp

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“…Dashed yellow lines depict the major tectonic boundaries of the Korean Peninsula (after Chough et al, 2000). Results of SKS-wave splitting measurements are compiled after Fouch and Fischer (1996), Fischer et al (1998), Long and van der Hilst (2006), Salah et al (2008), Wirth and Long (2008), Chang et al (2009), Kang andShin (2009), Salah et al (2009), where solid bars indicate the fast polarization direction and red circles are scaled to denote the delay time. Satellite image downloaded from GoogleEarth.…”

Section: Methodsmentioning

confidence: 99%

Relation between mantle shear zone deformation and metasomatism in spinel peridotite xenoliths of Jeju Island (South Korea): Evidence from olivine CPO and trace elements

Yang

Hidas

Falus³

et al. 2010

Journal of Geodynamics

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“…Absolute velocities and velocity contrasts between different structural and lithological bodies are imaged. Another source of information is seismic anisotropy, which is sometimes derived at high resolution using both approaches above, and also with seismic wave splitting measurements (Long and van der Hilst 2006). Seismic velocities and velocity are sensitive to lithology, anisotropy, pressure, temperature, and to free fluid content especially when overpressured.…”

Section: Seismologymentioning

confidence: 99%

Mantle hydration and Cl-rich fluids in the subduction forearc

Reynard

2016

Prog. in Earth and Planet. Sci.

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In the forearc region, aqueous fluids are released from the subducting slab at a rate depending on its thermal state. Escaping fluids tend to rise vertically unless they meet permeability barriers such as the deformed plate interface or the Moho of the overriding plate. Channeling of fluids along the plate interface and Moho may result in fluid overpressure in the oceanic crust, precipitation of quartz from fluids, and low Poisson ratio areas associated with tremors. Above the subducting plate, the forearc mantle wedge is the place of intense reactions between dehydration fluids from the subducting slab and ultramafic rocks leading to extensive serpentinization. The plate interface is mechanically decoupled, most likely in relation to serpentinization, thereby isolating the forearc mantle wedge from convection as a cold, potentially serpentinized and buoyant, body. Geophysical studies are unique probes to the interactions between fluids and rocks in the forearc mantle, and experimental constrains on rock properties allow inferring fluid migration and fluid-rock reactions from geophysical data. Seismic velocities reveal a high degree of serpentinization of the forearc mantle in hot subduction zones, and little serpentinization in the coldest subduction zones because the warmer the subduction zone, the higher the amount of water released by dehydration of hydrothermally altered oceanic lithosphere. Interpretation of seismic data from petrophysical constrain is limited by complex effects due to anisotropy that needs to be assessed both in the analysis and interpretation of seismic data. Electrical conductivity increases with increasing fluid content and temperature of the subduction. However, the forearc mantle of Northern Cascadia, the hottest subduction zone where extensive serpentinization was first demonstrated, shows only modest electrical conductivity. Electrical conductivity may vary not only with the thermal state of the subduction zone, but also with time for a given thermal state through variations of fluid salinity. High-Cl fluids produced by serpentinization can mix with the source rocks of the volcanic arc and explain geochemical signatures of primitive magma inclusions. Signature of deep high-Cl fluids was also identified in forearc hot springs. These observations suggest the existence of fluid circulations between the forearc mantle and the hot spring hydrothermal system or the volcanic arc. Such circulations are also evidenced by recent magnetotelluric profiles.

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Shear wave splitting from local events beneath the Ryukyu arc: Trench-parallel anisotropy in the mantle wedge

Cited by 141 publications

References 76 publications

Shear-wave anisotropy beneath the Ryukyu arc

Shear-wave anisotropy beneath the Ryukyu arc

Relation between mantle shear zone deformation and metasomatism in spinel peridotite xenoliths of Jeju Island (South Korea): Evidence from olivine CPO and trace elements

Mantle hydration and Cl-rich fluids in the subduction forearc

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