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首页> 外文期刊>Journal of geophysical research. Solid earth: JGR >Numerical Analysis of Time-Dependent Conduit Magma Flow in Dome-Forming Eruptions With Application to Mount St. Helens 2004-2008
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Numerical Analysis of Time-Dependent Conduit Magma Flow in Dome-Forming Eruptions With Application to Mount St. Helens 2004-2008

机译：2004-2008安装到圣海伦山圆顶成型爆发中的时间依赖导管岩浆流量的数值分析

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摘要

Conduit models of volcanic eruptions simulate magma evolution through phase transitions and material changes during ascent.We present a time-dependent one-dimensional model of a chamber-conduit system to examine the temporal evolution of dome-forming eruptions. As magma ascends, volatiles exsolve and may escape vertically through the column or laterally through the conduit walls. Magma solidifies which increases viscosity, leading to a natural transition from viscous flow at depth to frictional sliding along the conduit walls near the surface, resulting in the extrusion of a semisolid plug. The model evaluates time- and depth-dependent pressure, velocity, porosity, and relative amounts of exsolved water to carbon dioxide. Transient effects arise when magma outflux from the chamber appreciably decreases pressure over the magma ascent timescale. For low magma permeability, transient effects increase porosity and velocity relative to steady-state solutions. For high magma permeability, efficient vertical and lateral gas escape depresses porosity and velocity at later times.We use the model to predict three time series data sets from the 2004-2008 eruption of Mount St. Helens: extruded volume, ground deformation, and carbon dioxide emissions.We quantify sensitivity of model predictions to input parameters using the distance-based generalized sensitivity analysis. Chamber volatile content, volume, and excess pressure influence the amplitude of observables, while conduit radius, frictional rate dependence and magma permeability influence temporal evolution. High magma permeability can cause marked departures from exponentially decaying flux and may explain the unique temporal evolution of deformation observed at the only nearby continuous GPS station in operation at the eruption onset.
机译：火山爆发的导管模型通过相位过渡和上升期间的材料改变模拟岩浆进化.WE呈现腔室导管系统的时间依赖式一维模型，以检查圆顶形成爆发的时间演变。随着岩浆上升，挥发物exsolve，并且可以通过柱子垂直脱落或通过导管壁横向逸出。岩浆凝固，其增加粘度，导致从粘性流动的自然过渡到沿着表面附近的导管壁摩擦滑动，导致半固体塞的挤出。该模型评估exsolved水的时间和深度依赖的压力，速度，孔隙度和相对量的二氧化碳。当来自腔室的Magma Outflux明显降低岩浆上升时间尺寸时，出现瞬态效应。对于低岩浆渗透性，瞬态效果相对于稳态溶液增加孔隙率和速度。对于高岩浆渗透性，高效的垂直和横向气体逃生在后面的时间下抑制孔隙率和速度。我们使用模型预测从2004 - 2008年爆发的ST. Helens的2004-2008喷发三次序列数据集：挤出体积，地面变形和碳二氧化碳排放量。通过基于距离的广义敏感性分析量化模型预测对输入参数的敏感性。腔室挥发性含量，体积和过度压力影响可观察到的幅度，而导管半径，摩擦速率依赖性和岩浆渗透率影响时间进化。高岩浆渗透率可引起指数衰减通量的标记偏离，并且可以解释在爆发发作时在唯一的附近连续GPS站观察到的变形的独特时间演变。

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