Mantle flow and deformation of subducting slab at a plate junction

Morishige, Manabu; Honda, Sawao

doi:10.1016/j.epsl.2013.01.033

Cited by 22 publications

(22 citation statements)

References 48 publications

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“…The flow in the mantle wedge becomes 3-D (Figure 5b). The material in the mantle wedge first moves toward the slab in the trench-normal direction and then it is dragged down by the slab [e.g., Kneller and van Keken, 2008;Morishige and Honda, 2013;Wada et al, 2015]. The horizontal speed is lower near the bend of the slab.…”

Section: Resultsmentioning

confidence: 99%

Along‐arc variation in short‐term slow slip events caused by 3‐D fluid migration in subduction zones

Morishige

Keken

2017

JGR Solid Earth

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A strong correlation exists between the average slip rate by short‐term slow slip events (SSEs) and changes in the slab geometry in Cascadia and Nankai. The generation of short‐term SSEs is generally assumed to be related to the presence of fluids and we investigate the hypothesis that fluids released by metamorphic dehydration reactions migrate in 3‐D due to complex slab geometry. The associated along‐arc focusing of fluid flux is likely to cause higher average slip rate in certain patches. To test this hypothesis, we investigate how fluid migration is modified by along‐strike changes in slab geometry. We use a numerical model of two‐phase flow in subduction zones. In this model fluids migrate subparallel to the slab surface due to the anisotropic permeability inside a serpentinite layer just above the slab. In 3‐D, we find that fluids migrate in the maximum‐dip direction of the slab, rather than subparallel to the plate motion. As a result fluid paths concentrate with increasing porosity where the slab has a convex shape (and diverge with decreasing porosity where it has a concave shape). These results suggest that regions with a high average slip rate by short‐term SSEs in Cascadia and Nankai can be explained by 3‐D focusing of fluid migration. We predict a defocusing of fluids below the Kii Channel, Nankai, which may be the reason for the observed small slip by short‐term SSEs in this location.

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Section: Resultsmentioning

confidence: 99%

Along‐arc variation in short‐term slow slip events caused by 3‐D fluid migration in subduction zones

Morishige

Keken

2017

JGR Solid Earth

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“…Slab stagnation appears absent to the north suggesting that the junction is an actively deforming and rapidly modifying corner in this subduction zone. Morishige and Honda (2012) provide a fully dynamical model for this region that takes trench retreat and slab stagnation into account. While they focused on processes somewhat deeper than in the present study, they demonstrated significant along-arc deformation.…”

Section: Discussionmentioning

confidence: 99%

Thermal structure and intermediate-depth seismicity in the Tohoku-Hokkaido subduction zones

2012

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Abstract. The cause of intermediate-depth (> 40 km) seismicity in subduction zones is not well understood. The viability of proposed mechanisms, which include dehydration embrittlement, shear instabilities and the presence of fluids in general, depends significantly on local conditions, including pressure, temperature and composition. The wellinstrumented and well-studied subduction zone below Northern Japan (Tohoku and Hokkaido) provides an excellent testing ground to study the conditions under which intermediatedepth seismicity occurs. This study combines new finite element models that predict the dynamics and thermal structure of the Japan subduction system with a high-precision hypocenter data base. The upper plane of seismicity is principally contained in the crustal portion of the subducting slab and appears to thin and deepen within the crust at depths > 80 km. The disappearance of seismicity overlaps in most of the region with the predicted phase change of blueschist to hydrous eclogite, which forms a major dehydration front in the crust. The correlation between the thermally predicted blueschist-out boundary and the disappearance of seismicity breaks down in the transition from the northern Japan to Kurile arc below western Hokkaido. Adjusted models that take into account the seismically imaged modified upper mantle structure in this region fail to adequately recover the correlation that is seen below Tohoku and eastern Hokkaido. We conclude that the thermal structure below Western Hokkaido is significantly affected by timedependent, 3-D dynamics of the slab. This study generally supports the role of fluids in the generation of intermediatedepth seismicity.

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“…There are only a few studies focusing on an oblique subduction with 3‐D models which is appropriate for the transition into Hokkaido [e.g., Honda and Yoshida , ; Kneller and van Keken , ; Bengtson and van Keken , ]. The number of numerical studies which consider these two regions together is quite small [ Morishige et al ., ; Morishige and Honda , ]. Morishige and Honda [] showed that the along‐arc variation of seismic anisotropy [e.g., Nakajima et al ., ], subduction angle [e.g., Hayes et al ., ], and the slab behavior in the transition zone [e.g., Fukao et al ., ; Miller and Kennett , ] can be explained at least qualitatively by the effects of the trench shape.…”

Section: Introductionmentioning

confidence: 99%

Along‐arc variation in the 3‐D thermal structure around the junction between the Japan and Kurile arcs

Morishige

Keken

2014

Geochem Geophys Geosyst

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The thermal structure in subduction zones has a strong influence on seismogenesis and arc volcanism. Traditional 2-D models have been used to provide reasonable agreement between models and observations, but in a number of cases clear 3-D effects are present. One such case is in the Northern Japan subduction system. At the junction between Japan and Kurile arcs, surface heat flow and the occurrence of intermediate-depth seismicity are different than in the Tohoku and Hokkaido regions. We investigate the effects of 3-D slab geometry and a local deepening of slab-mantle decoupling depth on the thermal structure in this region based on 3-D finite element approach. We find that both effects produce the along-arc variation of slab surface temperature, which could reach $100 C. The warmer region arises through 3-D effects of thermal conduction and the colder region arises through localized slow incoming flow in the case where 3-D slab geometry is taken into account. 3-D flow arises where a local deepening of slab-mantle decoupling depth is assumed, which leads to both warmer and colder regions. The effects on surface heat flow are small. While intermediate-depth seismicity in the subducted crust is suggested to be controlled by temperature-dependent phase transitions, the predicted changes in thermal structure are not sufficient to cause the observed deepening of seismicity. This suggests that the thermal structure of this subduction zone may be more strongly influenced by time-dependent deformation of the overriding crust and slab.

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Mantle flow and deformation of subducting slab at a plate junction

Cited by 22 publications

References 48 publications

Along‐arc variation in short‐term slow slip events caused by 3‐D fluid migration in subduction zones

Along‐arc variation in short‐term slow slip events caused by 3‐D fluid migration in subduction zones

Thermal structure and intermediate-depth seismicity in the Tohoku-Hokkaido subduction zones

Along‐arc variation in the 3‐D thermal structure around the junction between the Japan and Kurile arcs

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