Collaborative Research: Seismic Waves from Volcanoes: Fully Coupled Time-Dependent Models of Fluid Flow Through Elastic Walled Conduits

合作研究：火山地震波：通过弹性壁管道的流体流动的完全耦合时变模型

• 批准号: 1114073
• 负责人: Eric Dunham
• 金额: $ 22.47万
• 依托单位: Stanford University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-07-01 至 2014-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1114073&HistoricalAwards=false
• 关键词: Collaborative; Research; Seismic; Waves; Volcanoes

Mitigating the risks associated with volcanoes requires a detailed understanding of the transport and eruption of magma through cracks and conduits in Earth's crust. Seismic waves excited by magma flow and its coupling to the elastic wall rocks can be used to place valuable constraints on parts of the volcanic system that are otherwise inaccessible. The complexity of observed seismic signals and the difficulty of modeling the coupled fluid-solid system present a formidable challenge. The objective of this collaborative proposal is to develop numerical models describing the high-speed flow of compressible, viscous fluids through narrow channels in elastic bodies, together with the propagation of seismic waves through the solid. The fluid and solid response is fully coupled: elastic deformation changes the cross-sectional area of the conduit through which fluid flows, and changes in fluid pressure push the conduit walls in and out, exciting seismic waves.Specifically, the project group will develop a provably stable and accurate numerical method for time-dependent quasi-one-dimensional fluid flow through conduits in a solid body, together with the elastodynamic response of that solid. The model will include changes in compressibility, sound speed, viscosity, and drag from gas exsolution. The code will be used first to explore the role of conduit wall deformation on steady state eruption dynamics. The group will then assess the stability of steady state eruption solutions. Preliminary analyses indicate that for sufficiently rapid flows, the fluid-solid system is unstable to long wavelength perturbations that appear as conduit wall oscillations of growing amplitude. One first focus will be on seismic waves from basaltic fissure eruptions within the currently implemented two-dimensional plane-strain framework. The group will then extend the model to the axisymmetric geometry appropriate for cylindrical conduits, and study seismic waves from explosive eruptions. Finally, they will calculate far-field body and surface waves and link the time dependence of equivalent single force and moment tensor representations to detailed source processes.This project is supported by the Geophysics and Petrology & Geochemistry Programs.

减轻与火山有关的风险需要详细了解岩浆通过地壳裂缝和管道的运输和喷发。由岩浆流激发的地震波及其与弹性围岩的耦合，可以用来对火山系统的某些部分施加有价值的限制，否则这些部分是无法进入的。观测到的地震信号的复杂性和流固耦合系统建模的困难提出了一个艰巨的挑战。这一合作提案的目的是建立数值模型，描述可压缩粘性流体通过弹性体中狭窄通道的高速流动，以及地震波通过固体的传播。流体和固体响应完全耦合：弹性变形改变了流体流过的管道的横截面积，流体压力的变化推动管道壁进出，激发地震波。具体来说，项目组将开发一种可证明稳定和精确的数值方法，用于在固体中通过管道的随时间变化的准一维流体流动，以及该固体的弹性动力学响应。该模型将包括可压缩性，声速，粘度和气体出溶阻力的变化。该代码将首先用于探索稳态喷发动力学的管道壁变形的作用。然后，该小组将评估稳态喷发解决方案的稳定性。初步分析表明，对于足够快的流动，流体-固体系统是不稳定的长波长的扰动，出现作为管道壁振荡的幅度不断增长。第一个重点将是在目前实施的二维平面应变框架内的玄武岩裂缝喷发的地震波。然后，该小组将把该模型扩展到适合于圆柱形管道的轴对称几何形状，并研究爆炸喷发产生的地震波。最后，他们将计算远场体波和表面波，并将等效单力和力矩张量表示的时间依赖性与详细的源过程联系起来。