Numerical Models of Mantle Convection and Plate Tectonics

理查兹-0003553地球动力学家最近跨越了一个重要的门槛，表明地幔对流的板块构造样式在包括岩石圈破坏的简单流变学描述的数值模型中自洽地出现。研究人员建议进一步开发地幔对流和板块构造的三维球形模型，以包括对岩石圈破坏或板块边界形成的更完整的物理处理。他们将使用标量“损伤理论”的张量扩展来解释根据最大剪切应变定向的增强弱化。一个合理的和重要的假设是，交替的脊变换的几何形状自然出现在这样的模型中，俯冲带的片面性也可能与断层带内的定向应变率弱化有关。岩石圈破坏流变学的各向异性公式需要拉格朗日跟踪，或平流，张量粘度-一个不平凡的任务，促进了他们开发的方法，用于跟踪地幔对流中的化学物质。研究人员还建议继续集中调查明显的岩石圈下低粘度区（LVZ）在促进板块构造中的作用。其他相关的工作将包括正在进行的地幔混合研究，核和地幔的热耦合，扩散板块边界的动力学，以及热化学羽流与板块尺度流动的相互作用。

Richards EAR-0003553 Geodynamicists have recently crossed a significant threshold by showing that plate tectonic styles of mantle convection arise self-consistently in numerical models that include simple rheological descriptions of lithospheric failure. The investigators propose to further develop 3-D spherical models of mantle convection and plate tectonics to include a more complete physical treatment of lithospheric failure, or plate boundary formation. They will use a tensor extension of scalar "damage theory" to account for enhanced weakening oriented according to maximum shear strain. A reasonable and significant hypothesis is that alternating ridge-transform geometries arise naturally in such models, and that the one-sidedness of subduction zones may also be related to oriented strain-rate weakening deep within fault zones. An anisotropic formulation of lithospheric failure rheology requires Lagrangian tracking, or advection, of tensor viscosity -- a non-trivial task facilitated by methods they have developed for tracking chemical species in mantle convection. The investigators also propose to continue their focussed investigation into the role of a pronounced sublithospheric low viscosity zone (LVZ) in promoting plate tectonics. Other related work supported by this grant will include ongoing studies of mantle mixing, thermal coupling of the core and mantle, the dynamics of diffuse plate boundaries, and interactions of thermo-chemical plumes with plate-scale flow.