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

玛格丽特·贾达梅克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博士将研究板块形状和流变学的三维变化对俯冲带地幔流动速度和方向的影响，包括地幔楔形中不同的水分含量和应变率相关粘度的影响。为了研究这一过程，Jadamec博士将构建基于观测的科科斯-加勒比海板块边界哥斯达黎加-尼加拉瓜部分的3D数值模型。作为NSF边缘图坎实验的一部分，哥斯达黎加-尼加拉瓜俯冲带在地震学上得到了很好的成像。这些信息将被用来构建板块几何结构和覆盖板块结构，以及约束沿走向的地幔楔体内水和/或熔融含量的变化。3D数值模型中的俯冲带参数将被系统地改变，以深入了解控制俯冲带中地幔流动的潜在物理因素。预测的三维地幔速度矢量场和计算的无限应变轴，将与从地球化学研究和地震各向异性观测中推断的地幔流速进行比较，目前地震各向异性的观测表明，哥斯达黎加和尼加拉瓜下方的地幔楔体存在快速和空间复杂的速度场。这些3D数值模型将揭示哥斯达黎加和尼加拉瓜下方明显的海沟平行流动，到目前为止，这种流动缺乏一个明确的、经过数量测试的解释。快速的3D地幔流动对俯冲带变形的时间尺度和地幔楔形体内的地球化学信号传输有影响。在教育部分，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的本科生地球物理和构造学课程。3D虚拟现实将被用来教授内在的3D概念，如地球核心、地幔和岩石圈的相对尺寸和体积、瓦达蒂-贝尼奥夫带的几何形状、三个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的计算和可视化中心合作完成，该中心有一个洞穴和一个3D展示墙。

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.