Finite Element Modeling of the Seismic and Permeability Properties of Partially Molten Upper Mantle

摘要 P.I.：Humphreys提案编号：97-11808 机构：俄勒冈州大学题目：部分熔融上地幔地震和渗透性的有限元模拟 部分熔融的上地幔岩石的频率相关的地震响应将使用粘弹性有限元计算机模拟来确定。 由于夹杂物形状的复杂性，这种两相材料的力学性能的解析解一直是难以捉摸的。 有限元网格是基于从实验室产生的部分熔融橄榄岩的分析产生的图像。 为了研究S波，网格应变与简单剪切作为边界条件的阶跃函数和时间步进前进，允许应力衰减的熔体流动和粘性松弛。 从这种压力中 频率相关复弹性衰减函数 计算模量，得到 的 与频率有关的地震速度和衰减 该方法具有基准性 通过 比较有限元 结果 到具有已知解析解的相对简单的情况（例如， 椭圆体和三重连接管形内含物）。 渗透率通过在网格化样品上施加压差并从大量流体运输计算网络的水力传导率来建模。

Abstract P.I.: Humphreys Proposal Number: 97-11808 Institution: University of Oregon Title: Finite element modeling of the seismic and permeability properties of partially molten upper mantle The frequency dependent seismic response of partially molten upper mantle rock is to be determined using viscoelastic finite element computer simulations. Analytic solutions for the mechanical properties of this two-phase material have been elusive because of the complexity of the inclusion shapes. The finite element meshes are based on images produced from analysis of laboratory produced partially molten peridotites. To investigate S-waves, the mesh is strained with a step function in simple shear as a boundary condition and time is stepped forward allowing stress to decay as the melt flows and relaxes viscously. From this stress decay function the frequency dependent complex elastic moduli are computed, yielding the frequency dependent seismic velocity and attenuation. The method is benchmarked by comparing finite element results to relatively simple cases with known analytic solution (e.g., ellipsoids and triple junction tubule-shaped inclusions). Permeability is modeled by applying a pressure differential across the meshed sample, and calculating the hydraulic conductivity of the network from the bulk fluid transport.