Influence of overriding plate geometry and rheology on subduction
Influence of overriding plate geometry and rheology on subduction
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压倒性板块几何形状和流变学对俯冲的影响
DOI：
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发表时间：
2012
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通讯作者：
R. Müller
中科院分区：
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作者：
N. Butterworth;L. Quevedo;G. Morra;R. Müller
俯冲动力学强烈地依赖于俯冲板片和相邻板块的几何形状和流变性，以及由沿着俯冲带的构造构型演化驱动的诱导地幔流。然而，由于计算资源的限制，这些过程以及相关的板块构造驱动力很难使用随时间变化的三维计算机模拟进行研究。我们用一种新的数值方法研究这些现象，使用BEM‐Earth，一种基于边界元法（BEM）和快速多极子（FM）实现的Stokes流求解器。初始的BEM-地球模型配置自洽地确定了整个岩石圈-地幔系统的演化，而无需在整个地球的球形环境中施加额外的约束。我们发现，没有覆盖板块的模型高估了海沟退缩65%，在20万年。模型运行此外，较高粘度的上覆板块与较高速度的俯冲板片有关，类似于更快的大洋板块俯冲到更坚硬的大陆岩石圈之下。在我们的模型中，极向流主导着下行板块和覆盖板块之间的耦合，覆盖板块中的沟槽正交长度变化引起的流动至少比沟槽平行宽度变化强1.2倍。然而，上覆板块的变形与其长度和宽度有关，较窄和较长的板块比较宽和较短的板块延伸得更多。
Subduction dynamics is strongly dependent on the geometry and rheology of the subducting slab and adjacent plates, as well as on the induced mantle flow driven by the evolution of tectonic configurations along subduction zones. However, these processes, and the associated plate tectonic driving forces, are difficult to study using time‐dependent 3‐dimensional computer simulations due to limitations in computing resources. We investigate these phenomena with a novel numerical approach, using BEM‐Earth, a Stokes flow solver based on the Boundary Element Method (BEM) with a Fast‐Multipole (FM) implementation. The initial BEM‐Earth model configurations self‐consistently determine the evolution of the entire lithosphere‐mantle system without imposing additional constraints in a whole‐Earth spherical setting. We find that models without an overriding plate overestimate trench retreat by 65% in a 20 m.y. model run. Also, higher viscosity overriding plates are associated with higher velocity subducting slabs, analogue to faster oceanic plates subducting beneath more rigid continental lithosphere. In our models poloidal flows dominate the coupling between the down‐going and overriding plates, with trench‐orthogonal length variations in overriding plates inducing flows at least ∼2× stronger than trench‐parallel width variations. However, deformation in the overriding plate is related to its length and width, with narrower and longer plates extending more than wider and shorter plates.