Improving subduction interface implementation in dynamic numerical models

Sandiford, Dan; Moresi, Louis

doi:10.5194/se-10-969-2019

Cited by 22 publications

(22 citation statements)

References 70 publications

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“…The initially uniformly thick (10 km) crust gradually thickens to ≈15 km as it descends into the trench. This is because slab rollback induces horizontal extension in the crust at upper plate depths which, in turn, thickens it locally within this region (cf., Beall et al, 2021;Sandiford and Moresi, 2019). The final, "mature" phase begins as the slab impinges on the lower mantle at a depth of 660 km.…”

Section: Geodynamic Evolutionmentioning

confidence: 99%

Slab Temperature Evolution Over the Lifetime of a Subduction Zone

Holt

Condit

2021

Geochem Geophys Geosyst

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The thermal evolution of subducting slabs controls a range of subduction processes, yet we lack a robust understanding of how thermal structure develops over a subduction zone's lifetime. We investigate the time‐dependence of slab thermal structure using dynamically consistent, time evolving models. Pressure‐temperature (P–T) conditions along the slab Moho and slab top exhibit substantial variability throughout the various phases of subduction: initiation, free sinking, and mature subduction. This variability occurs in response to time‐dependent subduction properties (e.g., fast vs. slow convergence) and thermal structure inherited from previous phases (e.g., due to upper plate aging). At a given depth, the slab cools rapidly during initiation, after which slower cooling occurs. In the case of the Moho, additional cooling occurs during the free sinking phase. We explore the implications of time‐dependent thermal structure on exhumed rocks and slab dehydration. Modeled slab top P–T paths span much of the P–T space associated with exhumed rocks, suggesting a significant component of recorded variability may have dynamic origins. Coupling our P–T profiles with thermodynamic models of oceanic lithosphere, we show that dehydrating ultramafic rocks at the slab Moho provide the bulk of hydrous fluid at subarc depths during the earliest phases. Over subsequent phases, these rocks carry fluids into the deeper mantle, and it is mafic crust along the slab top that releases water at subarc depths. We conclude that varying subduction conditions, and non‐steady‐state thermal structure, challenge the utility of kinematically driven models with constant subduction parameters, particularly for investigating thermal structure in the geological past.

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Section: Geodynamic Evolutionmentioning

confidence: 99%

Slab Temperature Evolution Over the Lifetime of a Subduction Zone

Holt

Condit

2021

Geochem Geophys Geosyst

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“…The setup is comparable to recent studies, where flow is driven entirely by the thermal density contrast of the plate slab, which develops as a naturally evolving thermal boundary layer at the surface (Agrusta et al., 2017; Garel et al., 2014). The model setup is described in detail in the supporting information S1 (see also Sandiford & Moresi, 2019). Mantle rheology (including oceanic lithosphere) is prescribed by a composite flow law including linear high‐temperature creep and a scalar viscoplasticity designed to capture both psuedo‐brittle as well as distributed plastic deformation within the slab.…”

Section: Insights From Numerical Modelingmentioning

confidence: 99%

The Fingerprints of Flexure in Slab Seismicity

et al. 2020

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Earthquake moment tensors in eastern Pacific (ePac) slabs typically show downdip tensional (DT) axes, whereas in the western Pacific (wPac), they typically show downdip compressional (DC) axes or have mixed orientations indicative of unbending. Prevailing conceptual models emphasize uniform stress/deformation modes, that is, bulk slab stretching or shortening, as the dominant control on intermediate depth seismic expression. In contrast, we propose that a diversity of seismic expression, including DT‐ and DC‐dominated regions, is consistent with expectations of flexural strain accumulation, based on systemic differences in slab geometry. Our analysis reveals two largely unrecognized features of ePac intraslab seismicity. First, earthquake clusters consistent with slab unbending are present in ePac slabs, albeit at much shallower depths than typical of wPac slabs. Second, intermediate depth ePac DT seismicity is strongly localized to the upper half of zones undergoing curvature increase, such as flat slab segments. Our study highlights how the seismic expression of slab flexure is impacted by the relative contribution of brittle and ductile deformation. The strongly asymmetric temperature structure that is preserved in sinking slabs means that seismicity disproportionately records the deformation regime in the colder part of the slab, above the neutral plane of bending. The expression of in‐plane stress may be discernible in terms of a systematic modifying effect on the seismic expression of flexure.

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“…Using these scaling factors and Equations 4 and 5, we can thus substitute the scaled parameters for their dimensionless counterparts in Equation 2, which after rearranging leads us to write the following dimensionless momentum conservation equation, similar to Sandiford and Moresi (2019):…”

Section: Scalingmentioning

confidence: 99%

Thermo‐Mechanical Numerical Modeling of the South American Subduction Zone: A Multi‐Parametric Investigation

Strak

Schellart

2021

JGR Solid Earth

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The South American subduction zone is characterized by unique features, including long-lived, uninterrupted subduction (e.g., Coira et al., 1982;Maloney et al., 2013;Schellart, 2017), slab sinking to great mantle depths and a very wide along-trench dimension (Figure 1). These factors likely impact on subduction dynamics (e.g., Faccenna et al., 2017;Schellart, 2017) and on the resulting slab geometry (Schellart, 2017), surficial velocities, and natural hazards. Building geodynamic models is key to improve our understanding of the complex South American subduction system. Running 3-D geodynamic subduction models would be an ideal approach to study the subduction zone dynamics. With the continued improvement in computational power (Jadamec, 2016), the development of 3-D geodynamic modeling becomes indeed more realistic. However, despite the powerful computational resources, running 3-D models remain an expensive task as the models can require months or years to complete (e.g., Schellart, 2017), in particular for such a large setting as the South American subduction zone. Therefore, we propose with this study to use 2-D models to do a parametric investigation of several independent physical parameters in order to test their effect on the subduction process and to calibrate these parameters for future modeling in 3D space. The two-dimensional approach is suited for this study since 2-D models well reproduce subduction dynamics at the central section of wide subduction zones, where toroidal mantle flow is minimal (Schellart, 2017(Schellart, , 2020Schellart et al., 2007).The objectives of this paper are twofold: (1) Calibrate independent variables for use in future 3-D modeling by comparing model outcomes with a range of geophysical and kinematic data of the central segment of the South American subduction zone (Bolivian orocline region). In order to find best-fitting values for the tested independent variables, we compare a range of dependent variables with the natural prototype including slab geometry and surficial velocities using tomography, seismology, and a kinematic reconstruction

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Improving subduction interface implementation in dynamic numerical models

Cited by 22 publications

References 70 publications

Slab Temperature Evolution Over the Lifetime of a Subduction Zone

Slab Temperature Evolution Over the Lifetime of a Subduction Zone

The Fingerprints of Flexure in Slab Seismicity

Thermo‐Mechanical Numerical Modeling of the South American Subduction Zone: A Multi‐Parametric Investigation

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