Dynamics of seismogenic volcanic extrusion at Mount St Helens in 2004-05
Dynamics of seismogenic volcanic extrusion at Mount St Helens in 2004-05
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DOI：
10.1038/nature05322
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发表时间：
2006-11-23
期刊：
影响因子：
64.8
通讯作者：
Vallance, James W.
中科院分区：
文献类型：
--
作者：
Iverson, Richard M.;Dzurisin, Daniel;Vallance, James W.
2004-05年的圣海伦火山爆发表现出持续的，接近平衡的行为，其特征是相对稳定的挤压固体英安岩塞和近周期性的浅层地震。在这里，我们提出了一个不同的数据集，以支持我们的假设，这些地震造成的粘滑运动沿着边缘的插头，因为它被迫逐步向上上升，凝固，气体贫乏的岩浆。我们正式这个假设的动力学模型，揭示了一个很强的类比之间的行为的岩浆塞系统和一个阻尼振荡器。模型化的粘滑振荡具有有助于限制控制地震和喷发的力的平衡的特性，它们意味着岩浆压力从未偏离稳定的平衡压力太多。我们推断，在2004年至2005年的火山爆发之前，火山可能早就处于接近爆发的平衡状态。
The 2004-05 eruption of Mount St Helens exhibited sustained, near-equilibrium behaviour characterized by relatively steady extrusion of a solid dacite plug and nearly periodic shallow earthquakes. Here we present a diverse data set to support our hypothesis that these earthquakes resulted from stick-slip motion along the margins of the plug as it was forced incrementally upwards by ascending, solidifying, gas-poor magma. We formalize this hypothesis with a dynamical model that reveals a strong analogy between behaviour of the magma-plug system and that of a variably damped oscillator. Modelled stick-slip oscillations have properties that help constrain the balance of forces governing the earthquakes and eruption, and they imply that magma pressure never deviated much from the steady equilibrium pressure. We infer that the volcano was probably poised in a near-eruptive equilibrium state long before the onset of the 2004-05 eruption.