海山俯冲过程中的变形特征——物理模拟和数值模拟证据

Deformation of seamount during subduction:Insights from sandbox experiment and numerical simulation

文章通过物理模拟和数值模拟相结合的方法, 探讨了海山在俯冲过程中自身出现的变化特征.结果表明, 海山在增生楔体中俯冲时, 主要变化特征表现为其上覆的大洋沉积物的刮落, 唯有海山尾部的洋壳有小部分大洋沉积物得以保存; 当海山开始进入俯冲通道时, 海山逐渐由向陆壳之下硬挤入变为向地幔挠曲, 而向地幔的挠曲变形为海山进入俯冲提供了充足的空间并使俯冲洋壳的俯冲角度增加.俯冲挠曲过程有效降低了陆壳与海山之间的耦合度, 从而降低大震的发生概率.此外, 文章也对多手段研究俯冲带变形的尝试进行了探讨.

Using sandbox experiment and numerical simulation,we discussed deformation of a subducting seamount. Our results showed that the deformation mainly concentrated at the overlain ocean sediment when a seamount subducted beneath the accretionary wedge. The sediment was scraped into wedge,while the part in the tailing of the seamount was well stored. After the seamount entered the subduction channel,the oceanic crust began to bend downward. The bending provided more space for seamount subduction and caused the subduction angle increased. Above described subduction process decreased the coupling between seamount and continental crust,leading to occurrences of megathrust earthquakes largely reduced. This study also represented an attempt to investigate deformation of a subduction zone by multi-methods.