Effects of Elasticity on Subduction Initiation: Insight From 2‐D Thermomechanical Models
Effects of Elasticity on Subduction Initiation: Insight From 2‐D Thermomechanical Models
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DOI：
10.1029/2022jb024400
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发表时间：
2022-10
期刊：
影响因子：
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通讯作者：
Xin Zhou;I. Wada
中科院分区：
文献类型：
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作者：
Xin Zhou;I. Wada
尽管广泛的建模工作，动力学的俯冲启动（SI），包括弹性的作用，并没有完全理解。使用具有粘塑性（VP）和粘弹塑性（VEP）流变学的二维热机械模型，我们使用两种模型设置系统地研究了弹性在海洋内SI中的作用：无强制收敛的自发引发和强制收敛的诱导引发。在自发模型中，覆盖板年龄为50 Ma通常会导致垂直驱动的SI与流变学，但对于一个给定的年龄对比，SI更容易发生与VEP流变学。在任一流变模型中，当两个板块都是年轻的，有一个小的年龄对比，所产生的SI是水平驱动的，和弹性不影响SI显着，无论收敛速度。然而，当热年龄对比大，收敛速度相对较低，在诱导模型中的SI是垂直驱动的，类似于在自发模型中，和VEP流变导致更快的SI比VP流变。这种弹性效应随着初始水平压应力的增大而减小，但在初始压应力<1000MPa时并不完全消失。因此，包括弹性与合理的剪切模量和初始应力值的结果在一个较弱的板，使其更容易发生垂直驱动SI时，年龄对比相对较大。
Despite extensive modeling efforts, the dynamics of subduction initiation (SI), including the role of elasticity, are not fully understood. Using two‐dimensional thermomechanical models with visco‐plastic (VP) and visco‐elasto‐plastic (VEP) rheologies, we systematically investigate the role of elasticity in intraoceanic SI using two model setups: spontaneous initiation without imposed convergence and induced initiation with imposed convergence. In spontaneous models, the overriding plate age of 50 Ma generally lead to vertically driven SI with either rheology, but for a given age contrast, SI is easier to occur with the VEP rheology. In induced model with either rheology, when the two plates are young and have a small age contrast, the resulting SI is horizontally driven, and elasticity does not affect SI significantly, regardless of the convergence rate. However, when the thermal age contrast is large and a convergence rate is relatively low, the SI in induced models is vertically driven and similar to that in the spontaneous models, and the VEP rheology leads to faster SI than the VP rheology. This effect of elasticity becomes smaller with increasing initial horizontal compressional stress but does not become fully negated by the initial stress of <∼50 MPa. Therefore, inclusion of elasticity with reasonable shear modulus and initial stress values results in a weaker slab, making it easier for vertically driven SI to occur when the age contrast is relatively large.