Construction of semi-dynamic model of subduction zone with given plate kinematics in 3D sphere

Morishige, Manabu; Honda, Sawao; Tackley, P. J.

doi:10.5047/eps.2010.09.002

Cited by 14 publications

(15 citation statements)

References 17 publications

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“…In order to allow the subducting plate to freely extend laterally in the process of subduction, the transform fault is considered in a latitudinal boundary of subducting plate. In order to realize the subducting plate at a trench, we applied a semi‐dynamic model of subduction zone developed in the work of Honda [2008] and Morishige et al [2010]. Following their works, the flow is imposed a priori at the top surface boundary and in a small region around the trench (hereafter called “boundary region,” see Figure 4b) by keeping the mass conservation at each time step (see Honda [2008] and Morishige et al [2010] for details, see also Appendix A).…”

Section: Model Descriptionsmentioning

confidence: 99%

The 3D numerical modeling of subduction dynamics: Plate stagnation and segmentation, and crustal advection in the wet mantle transition zone

et al. 2012

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[1] Water content in the mantle transition zone (MTZ) has been broadly debated in the Earth science community as a key issue for plate dynamics. In this study, a systematic series of three-dimensional (3D) numerical simulation are performed in an attempt to verify a hypothesis regarding the behavior of subducted oceanic plate and the role of crust in the MTZ under wet conditions. This hypothesis is based on the seismic observations of structural variations associated with large-scale flattened high velocity anomalies (i.e., stagnant slabs) in the MTZ. In our model, weak (low-viscosity) fault zones (WFZs), which presumably correspond to the fault boundaries of large subduction earthquakes, are imposed on the top part of subducting plates. The phase transitions of olivine to wadsleyite and ringwoodite to perovskite+magnesiowüstite under both "dry" and "wet" conditions are considered based on recent high pressure experiments. The effect of viscosity reduction of wet garnet is also considered for oceanic crust in the MTZ. Results show that there is a substantial difference in the behaviors of subducting plate and the trace of crustal materials between the models under dry and wet conditions. Under wet conditions the subducting plate tends to stagnate with a maximum lateral extent of over 1000 km. The weaker and denser crustal material (garnet rich) is fed into the WFZs and is advected faster than the plate main body of peridotite (olivine rich). Thus, the viscosity and density contrast between the crustal materials and the peridotite permits the plate segmentation under a wet MTZ condition.Citation: Yoshida, M., F. Tajima, S. Honda, and M. Morishige (2012), The 3D numerical modeling of subduction dynamics: Plate stagnation and segmentation, and crustal advection in the wet mantle transition zone,

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Section: Model Descriptionsmentioning

confidence: 99%

The 3D numerical modeling of subduction dynamics: Plate stagnation and segmentation, and crustal advection in the wet mantle transition zone

et al. 2012

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“…There is no rollback‐induced poloidal circulation around the slab tip in these two models. The general flow patterns are similar to those in the models without overriding lithosphere [e.g., Stegman et al ., ; Di Giuseppe et al ., ; Schellart , ], except that in this study mantle circulation is modulated by the overriding lithosphere and the neighboring plate as shown in recent models with surrounding lithospheres and Newtonian mantle viscosity [e.g., Yamato et al ., ; Morishige et al ., ]. The coupling with the stagnant overriding lithosphere, together with the shearing between the plates affect the geometry of the convection cell around the slab edge (Figures a and c).…”

Section: Resultsmentioning

confidence: 99%

Trench‐parallel flow in the southern Ryukyu subduction system: Effects of progressive rifting of the overriding plate

Lin

Kuo

2013

JGR Solid Earth

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[1] The Okinawa trough in the Ryukyu subduction system is one of a few actively extending back arc basins within the continental lithosphere. Recent shear-wave splitting measurements show variable fast directions along the trough suggesting a complex threedimensional mantle flow field. In this study we use numerical subduction models to demonstrate that the thickness variations of the continental lithosphere bounding the edge of a subduction zone can result in complicated mantle circulation and regional dynamics. The model results for the southern Ryukyu show a combination of two effects: Along the Okinawa trough, the increasing thickness of the overriding Eurasian plate toward Taiwan due to a gradually diminishing rifting induces pressure gradients that drive trench-parallel flow to the edge in the shallow portion of the mantle wedge, and the thick Eurasian lithosphere to the west effectively blocks and diverts this along-arc flow and limits the toroidal flow around the slab edge below it. The toroidal flow thus enters the mantle wedge at depths of more than about 100 km, opposite in direction with and largely below the along-arc flow. These combined geometry effects of the Eurasian lithosphere create an intricate three-dimensional flow structure at the southern edge of the Ryukyu subduction zone. Model predictions for lattice preferred orientations of olivine aggregates show rotation patterns that agree with the observed shear-wave splitting patterns. This threedimensional scenario echoes the geochemical and seismological evidence worldwide that indicates complex, depth-varying mantle circulations in subduction systems.

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“… Nakajima et al [2006] showed that the fast direction of shear wave splitting in the back‐arc of the Tohoku region corresponds to the maximum dip direction of the subducting Pacific plate, rather than to the direction of plate convergence. Actually, Kneller and van Keken [2007, 2008] and Morishige et al [2010] show the existence of trench‐normal flow in their 3D modeling of oblique subduction. It may also be caused by other types of movement which are not directly associated with the subducting slab.…”

Section: Discussionmentioning

confidence: 99%

Three-dimensional structure of P-wave anisotropy in the presence of small-scale convection in the mantle wedge

Morishige

Honda

2011

Geochem. Geophys. Geosyst.

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[1] As a possible explanation of "hot fingers" in the mantle wedge below the Tohoku region, Japan, the existence of small-scale convection has been proposed. In this study, we performed numerical calculations around the subduction zone in 3D with composite rheology (i.e., a combination of linear and non-linear rheology) and found that small-scale convection could arise when the rheology determined from laboratory experiments is considered. We also calculated 3D structure of expected P-wave anisotropy for the case with and without small-scale convection based on a theory of LPO development and an assumption that anisotropy is approximately represented as hexagonal symmetry, and found that the fast axis of the P-wave propagation projected on the horizontal cross-sections is nearly in the same direction as that of plate motion in many places. It implies that effects of large-scale mantle flow associated with subducting slab is still dominant even in the presence of small-scale convection in mantle wedge. However, in vertical crosssections, the projected fast axis of the P-wave propagation could tilt vertically while that without small-scale convection is almost horizontal. Therefore, future seismological studies that determine the fast direction of P-wave propagation in 3D would give us critical information on the possible existence of small-scale convection in the mantle wedge.

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Construction of semi-dynamic model of subduction zone with given plate kinematics in 3D sphere

Cited by 14 publications

References 17 publications

The 3D numerical modeling of subduction dynamics: Plate stagnation and segmentation, and crustal advection in the wet mantle transition zone

The 3D numerical modeling of subduction dynamics: Plate stagnation and segmentation, and crustal advection in the wet mantle transition zone

Trench‐parallel flow in the southern Ryukyu subduction system: Effects of progressive rifting of the overriding plate

Three-dimensional structure of P-wave anisotropy in the presence of small-scale convection in the mantle wedge

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