Modeling Post-Glacial Rebound for Earth with 3-D Viscoelastic Structures

我们对地球动力学演化的理解关键取决于我们对地幔黏性结构的了解。冰期后的回弹过程对这种构造提供了最重要和最直接的限制。在过去的三十年中，通过比较模型预测和冰期后反弹数据，大量的研究致力于约束地幔粘度。几乎所有这些研究都假设地球的粘弹性结构是一维的，只依赖于半径——这一条件大大简化了建模过程。然而，在地幔和岩石圈中存在重要的横向变化粘弹性结构，包括岩石圈厚度变化、断裂板块边界、大陆龙骨以及各种地震层析成像模型所暗示的其他结构。研究人员建议开发球形有限元模型，以研究具有真实三维粘弹性结构（包括大陆龙骨）的地幔的冰川后反弹过程，以及各种地震层析模型所隐含的其他结构。他们将研究由横向变化的结构引起的不同程度和阶次的球面谐波之间的耦合，并将研究这种耦合对冰期后反弹观测的可能影响。在拟议的研究中，他们将使用已经开发的有限元软件CitcomS来模拟球形壳中具有可变粘度的热对流。他们还将扩展CitcomS，将粘弹性（例如Maxwell）流变学和可变形网格结合起来。

Zhong and Wahr 0087567 Our understanding of the dynamic evolution of the Earth hinges critically on our knowledge of the mantle's viscosity structure. The post-glacial rebound process provides the most important and direct constraints on that structure. In the last three decades, a large number of studies have been devoted to constraining mantle viscosity by comparing model predictions and post-glacial rebound data. Almost all these studies have assumed that the Earth's viscoelastic structure is one-dimensional with dependence only on radius -- a condition that greatly simplifies the modeling process. However, important laterally varying viscoelastic structures exist in the mantle and lithosphere, including lithospheric thickness variations, faulted plate boundaries, continental keels, and other structures implied by a variety of seismic tomography models. The investigators propose to develop spherical finite element models to study the post-glacial rebound process for a mantle with realistic 3-D viscoelastic structures that include continental keels, and other structures implied by a variety of seismic tomography models. They will study the coupling between spherical harmonics with different degrees and orders induced by the laterally varying structure, and will examine the possible effects of that coupling on post-glacial rebound observations. For the proposed research, theywill use a finite element software CitcomS that has been developed to model thermal convection with variable viscosity in a spherical shell. They will also extend CitcomS to incorporate a viscoelastic (e.g., Maxwell) rheology and a deformable grid.