Role of Rheology and Water in Rapid Mantle Flow: 3D Numerical Models of the Costa Rica-Nicaragua Subduction Zone

margaret Jadamec博士被授予美国国家科学基金会地球科学博士后奖学金，在布朗大学开展研究和教育计划。Jadamec博士将研究三维变化在板块形状和流变学中的作用，包括地幔楔中可变含水量和应变速率相关粘度对俯冲带地幔流动速率和方向的影响。为了研究这一过程，Jadamec博士将建立基于观测的哥斯达黎加-尼加拉瓜部分的可可斯-加勒比板块边界的三维数值模型。作为美国国家科学基金会边缘TUCAN实验的一部分，哥斯达黎加-尼加拉瓜俯冲带已经得到了很好的地震成像。这些信息将用于构造板块几何形状和覆盖板块结构，以及约束地幔楔内水和/或熔融物含量的沿走向变化。三维数值模型中的俯冲带参数将系统地变化，以深入了解控制俯冲带地幔流动的底层物理。预测的三维地幔速度矢量场和计算的无限应变轴将与地球化学研究和地震各向异性观测推断的地幔流率进行比较，目前这些研究表明哥斯达黎加和尼加拉瓜地下地幔楔存在快速且空间复杂的速度场。这些三维数值模型将揭示哥斯达黎加和尼加拉瓜地下明显的海沟平行流，迄今为止还缺乏一个明确的、经过定量检验的解释。快速三维地幔流动对俯冲带变形的时间尺度和地幔楔内地球化学特征的传递具有重要意义。在教育方面，Jadamec博士将把3D沉浸式虚拟现实（VR）实验室练习纳入布朗大学（Brown University）的地球物理学和构造学本科课程。3D VR将用于教授固有的3D概念，例如地核、地幔和岩石圈的相对尺寸和体积，Wadati-Benioff带的几何形状，三重连接点的空间连接以及地震层析成像。这项工作将与布朗大学计算与可视化中心合作完成，该中心既有一个洞穴，也有一个3D显示墙。

Dr. Margarete Jadamec is awarded an NSF Earth Science Postdoctoral Fellowship to carry out a research and education plan at Brown University. Dr. Jadamec will investigate the role of 3D variations in slab shape and rheology, including the effects of variable water content in the mantle wedge and a strain-rate dependent viscosity, on the rate and direction of mantle flow in subduction zones. To study this process, Dr. Jadamec will construct observationally based 3D numerical models of the Costa Rica-Nicaragua portion of the Cocos-Caribbean plate boundary. As part of the NSF MARGINS TUCAN experiment, the Costa Rica-Nicaragua subduction zone has been well imaged seismologically. This information will be used to construct the slab geometry and overriding plate structure, as well as to constrain the along strike changes in water and/or melt content within the mantle wedge. Subduction zone parameters in the 3D numerical models will be systematically varied to gain insight into the underlying physics that govern mantle flow in subduction zones. The predicted 3D mantle velocity vector field, and calculated infinite strain axes, will be compared to mantle flow rates inferred from geochemical studies and observations of seismic anisotropy, which presently suggest a fast and spatially complex velocity field in the mantle wedge beneath Costa Rica and Nicaragua. These 3D numerical models will shed light on the apparent trench parallel flow beneath Costa Rica and Nicaragua, which to date lacks a clear, quantitatively-tested explanation. Rapid 3D mantle flow has implications for the timescales of deformation in subduction zones and the transport of geochemical signatures within the mantle wedge.For the educational component, Dr. Jadamec will incorporate 3D immersive virtual reality (VR) laboratory exercises into undergraduate geophysics and tectonics courses at Brown University. The 3D VR will be used to teach inherently 3D concepts such as the relative dimensions and volumes of the Earth's core, mantle, and lithosphere, the geometry of Wadati-Benioff zones, the spatial connections in triple junctions, and seismic tomography. This work will be done in collaboration with Brown University's Center for Computation and Visualization, which has both a CAVE and a 3D display wall.