Face-to-face double subduction systems, in which two oceanic plates subduct toward each other, are essential elements of plate tectonics. Two subduction zones in such systems are typically uneven in age and their spatially and temporally variable dynamics remain enigmatic. Here, with 2D numerical modelling, we demonstrate that the onset of the younger subduction zone strongly changes the dynamics of the older subduction zone. The waxing younger subduction may gradually absorb plate convergence from the older one, resulting in older subduction waning featured by the dramatic decrease in subduction rate and trench retreat. The dynamical transformation of subduction predominance alters the intraplate stress and mantle flow, regulating the relative motion among the three different plates. The process of waxing and waning of subduction zones controls plate motion reorganisation, providing a reference to interpret the past, present, and future evolution of several key double subduction regions found on the modern Earth.

面对面的双俯冲系统，其中两个海洋板块相互俯冲，是板块构造的基本要素。此类系统中的两个俯冲带通常年龄不均，并且它们的空间和时间变化动态仍然是个谜。在这里，通过二维数值模拟，我们证明了较年轻的俯冲带的开始强烈改变了较老的俯冲带的动力学。较年轻的俯冲逐渐增强，可能会逐渐吸收较老俯冲的板块辐合，导致较老俯冲减弱，其特征是俯冲速率急剧下降和海沟后退。俯冲优势的动力学转变改变了板内应力和地幔流，调节了三个不同板块之间的相对运动。俯冲带的盈亏过程控制着板块运动重组，为解释现代地球上几个关键双俯冲区的过去、现在和未来演化提供了参考。