A simple force balance model of subduction initiation
A simple force balance model of subduction initiation
复制标题
俯冲起始的简单力平衡模型
DOI：
10.1093/gji/ggac332
复制
发表时间：
2022
影响因子：
2.8
通讯作者：
Gurnis, Michael
中科院分区：
文献类型：
--
作者：
Li, Yida;Gurnis, Michael
俯冲带的形成和发展与板块内部和板块边界的巨大应力变化有关。我们制定了一个简单的分析模型的基础上的力平衡方程的俯冲带，并验证它与高度非线性，耦合热力系统的数值计算。在远场固定速度和固定力两种边界条件下，定量分析了力平衡方程中板片拉力、板间摩擦力、板片弯曲和基底牵引力等各分量对俯冲板块运动学和应力状态的影响。基于数值和分析模型，我们讨论了板块曲率的演变，塑性屈服和弹性的作用，以及不同的因素如何影响俯冲开始的时间。我们证明了对于厚度为H的板，存在塑性屈服时，弯曲力与H2成正比，而不是以前认为的H3。虽然弹性增加了开始成核俯冲所需的力，但当屈服应力较小时，它基本上不会改变开始俯冲带所需的总功。该分析模型提供了一个很好的适合的总工作和时间开始俯冲和力和速度作为收敛和时间的函数。成核过程中的板块会聚和弱化速率是影响板块力平衡的主要因素，通常需要200公里的板块会聚才能使新生俯冲带进入自我维持状态。封闭形式的解决方案现在提供了一个框架，可以更好地解释三维中更复杂的时间依赖系统。
The initiation and development of subduction zones are associated with substantial stress changes both within plates and at plate boundaries. We formulate a simple analytical model based on the force balance equation of a subduction zone, and validate it with numerical calculations of highly non-linear, coupled thermomechanical system. With two kinds of boundary conditions with either fixed velocity or fixed force in the far-field, we quantitatively analyse the role of each component in the force balance equation, including slab pull, interplate friction, plate bending and basal traction, on the kinematics and stress state of a subducting plate. Based on the numerical and analytical models, we discuss the evolution of plate curvature, the role of plastic yielding and elasticity, and how different factors affect the timing of subduction initiation. We demonstrate with the presence of plastic yielding for a plate of thickness,H, that the bending force is proportional toH2, instead ofH3as previously thought. Although elasticity increases the force required to start nucleating subduction it does not substantially change the total work required to initiate a subduction zone when the yielding stress is small. The analytical model provides an excellent fit to the total work and time to initiate subduction and the force and velocity as a function of convergence and time. Plate convergence and weakening rate during nucleation are the dominant factors influencing the force balance of the plate, and 200 km of plate convergence is typically required to bring a nascent subduction zone into a self-sustaining state. The closed-form solution now provides a framework to better interpret even more complex, time-dependent systems in three dimensions.