Evolution of Subduction Zone Curvature and its Dependence on the Trench Velocity and the Slab to Upper Mantle Viscosity Ratio

Schellart, Wouter P.

doi:10.1029/2009jb006643

Cited by 51 publications

(46 citation statements)

References 80 publications

(161 reference statements)

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“…The olivine fabrics in the anhydrous aseismic PHS slab may change to D-type because of high stress induced by slab bending, for which seismic anisotropy is V x > V y > V z . In a number of subduction zones on Earth, the slab geometry generally shows an increasing dip angle at a greater depth in the mantle, possibly affected by trench retreat and slab rollback 47 . Thus, the above-mentioned x and z axes for the olivine fabric in the slab rotated counterclockwise and replaced each other with unchanged y axis, and V x is the velocity in the vertical direction while V z and V y are the velocities in the horizontal plane.…”

Section: Discussionmentioning

confidence: 99%

Seismic anisotropy evidence for dehydration embrittlement triggering intermediate-depth earthquakes

Wang

Zhao

Yao

2017

Sci Rep

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It has been proposed that dehydration embrittlement of hydrous materials can trigger intermediate-depth earthquakes and form a double seismic zone in a subducting slab. Seismic anisotropy may provide a possible insight into intermediate-depth intraslab seismicity, because anisotropic properties of minerals change with varying water distribution, temperature and pressure. Here we present a high-resolution model of P-wave radial anisotropy tomography of the Japan subduction zone down to ~400 km depth, which is obtained using a large number of arrival-time data of local earthquakes and teleseismic events. Our results reveal a close correlation between the pattern of intermediate-depth seismicity and anisotropic structures. The seismicity occurs in portions of the Pacific and Philippine Sea slabs where positive radial anisotropy (i.e., horizontal velocity being faster than vertical one) dominates due to dehydration, whereas the inferred anhydrous parts of the slabs are found to be aseismic where negative radial anisotropy (i.e., vertical velocity being faster than horizontal one) dominates. Our anisotropic results suggest that intermediate-depth earthquakes in Japan could be triggered by dehydration embrittlement of hydrous minerals in the subducting slabs.

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Section: Discussionmentioning

confidence: 99%

Seismic anisotropy evidence for dehydration embrittlement triggering intermediate-depth earthquakes

Wang

Zhao

Yao

2017

Sci Rep

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“…The toroidal flow of the mantle around the eastern Alaska slab edge and steepening of the slab dip predicted by the 3D models of the Alaska subduction‐transform system are suggestive of slab rollback [ Garfunkel et al , 1986; Kincaid and Griffiths , 2003; Schellart , 2004; Funiciello et al , 2006; Stegman et al , 2006] and thereby retreat of the trench in eastern Alaska. 3D laboratory experiments of free subduction indicate that during trench retreat, the trench geometry evolves into an arcuate shape with the concave side directed away from subducting plate [ Schellart , 2004; Funiciello et al , 2006; Schellart , 2010a]. Along the greater than 3000 km length of the Aleutian‐Alaska subduction zone, the sense of curvature of the plate boundary changes concavity [ Page et al , 1989; Gudmundsson and Sambridge , 1998; Ratchkovski and Hansen , 2002; Bird , 2003].…”

Section: Discussionmentioning

confidence: 99%

The role of rheology and slab shape on rapid mantle flow: Three‐dimensional numerical models of the Alaska slab edge

2012

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[1] Away from subduction zones, the surface motion of oceanic plates is well correlated with mantle flow direction, as inferred from seismic anisotropy. However, this correlation breaks down near subduction zones, where shear wave splitting studies suggest the mantle flow direction is spatially variable and commonly non-parallel to plate motions. This implies local decoupling of mantle flow from surface plate motions, yet the magnitude of this decoupling is poorly constrained. We use 3D numerical models of the eastern Alaska subduction-transform plate boundary system to further explore this decoupling, in terms of both direction and magnitude. Specifically, we investigate the role of the slab geometry and rheology on the mantle flow velocity at a slab edge. The subducting plate geometry is based on Wadati-Benioff zone seismicity and tomography, and the 3D thermal structure for both the subducting and overriding plates, is constrained by geologic and geophysical observations. In models using the composite viscosity, a laterally variable mantle viscosity emerges as a consequence of the lateral variations in the mantle flow and strain rate. Spatially variable mantle velocity magnitudes are predicted, with localized fast velocities (greater than 80 cm/yr) close to the slab where the negative buoyancy of the slab drives the flow. The same models produce surface plate motions of less than 10 cm/yr, comparable to observed plate motions. These results show a power law rheology, i.e., one that includes the effects of the dislocation creep deformation mechanism, can explain both observations of seismic anisotropy and decoupling of mantle flow from surface motion.Citation: Jadamec, M. A., and M. I. Billen (2012), The role of rheology and slab shape on rapid mantle flow: Three-dimensional numerical models of the Alaska slab edge,

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“…The general subduction evolution of the models is similar to previous laboratory and numerical models of progressive subduction in three‐dimensional space that use a similar (low) slab to upper mantle effective viscosity ratio ( η SP / η UM ≈ 10 2 ). Earlier narrow‐slab models also showed rapid trench retreat and a trench curvature that is concave toward the mantle wedge [e.g., Stegman et al , 2006; Morra et al , 2006; Schellart , 2004, 2010; Schellart et al , 2007], and wide‐slab models also showed slow trench migration and an overall convex trench geometry with concave edges [ Schellart et al , 2007; OzBench et al , 2008; Stegman et al , 2010b]. …”

Section: Discussionmentioning

confidence: 99%

Influence of lateral slab edge distance on plate velocity, trench velocity, and subduction partitioning

et al. 2011

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[1] Subduction of oceanic lithosphere occurs through both trenchward subducting plate motion and trench retreat. We investigate how subducting plate velocity, trench velocity and the partitioning of these two velocity components vary for individual subduction zone segments as a function of proximity to the closest lateral slab edge (D SE ). We present a global compilation for 207 trench segments from 17 active subduction zones on Earth and three-dimensional numerical models of progressive free subduction of a single oceanic plate that subducts into a stratified mantle. The results show that the subducting plate velocity is always high (≥5.1 cm/yr (models) and ≥4.2 cm/yr (nature)) and trench velocity is always low (≤2.5 cm/yr (models) and ≤1.7 cm/yr (nature)) in the center of wide subduction zones (D SE > 2200 km). Only in regions close to lateral slab edges (D SE < 1000 km), be it for narrow or wide subduction zones, can the trench velocity exceed 4 cm/yr (models) and 6 cm/yr (nature) and can the subducting plate velocity go below 4 cm/yr (models) and 2 cm/yr (nature). In general, plate velocities, trench velocities and subduction partitioning are much more variable near slab edges than in the center of wide subduction zones owing to other parameters that affect subduction kinematics. We conclude that subduction kinematics can vary considerably along individual subduction zones and that the upper bound values for trench velocity and lower bound values for subducting plate velocity and subduction partitioning at individual subduction zone segments depend critically on D SE .

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Evolution of Subduction Zone Curvature and its Dependence on the Trench Velocity and the Slab to Upper Mantle Viscosity Ratio

Cited by 51 publications

References 80 publications

Seismic anisotropy evidence for dehydration embrittlement triggering intermediate-depth earthquakes

Seismic anisotropy evidence for dehydration embrittlement triggering intermediate-depth earthquakes

The role of rheology and slab shape on rapid mantle flow: Three‐dimensional numerical models of the Alaska slab edge

Influence of lateral slab edge distance on plate velocity, trench velocity, and subduction partitioning

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