Conduit Evolution during the 1992 Eruptive Sequence at Mt. Spurr, Alaska

通过浅层管道的岩浆向上迁移在火山活动中起着重要作用，因为岩浆在上升过程中所经历的物理变化可能决定了由此产生的喷发的方式和强度。然而，关于火山导管的形状，它们在喷发过程中的演变，或者管道形状对岩浆上升速度的影响，人们知之甚少。我们建议分析1992年火山喷发期间的导管演化。通过使用单个地震来确定管道周围的应力场，以确定喷发序列不同阶段的应力场。这项工作将补充和检验已经完成的关于斯普尔喷发序列的大量地震和岩石学研究的结果。我们特别感兴趣的是确定管道在(1)在第一次爆发之前的十个月的活动期间的应力状态，(2)喷发内时期[1992年6-9月]，和(3)喷发后时期。对这三个时间段的评估将使我们能够评估喷发活动之前岩浆上升的条件，检查管道对个别喷发的响应，并检验1992年11月和12月的地震群实际上是因为浅层形成了固化的塞子而“失败”的假设。因此，我们的结果将提供对1992年山上喷发的洞察。Spur和辅助开发了应力场对岩浆运移事件响应的一般模型。此外，我们将把我们的结果与伊利姆纳火山附近岩脉侵位的应力场研究结果进行比较，以期揭示促进或阻碍侵入岩浆传播到地表的条件，从而改进对火山地区未来地震危机的解释。

EAR-0229655CashmanThe upward migration of magma through shallow conduits plays an important role in volcanic activity, as the physical changes that magma undergoes during ascent may determine the style and intensity of the resulting eruption. However, little is known about the shapes of volcanic conduits, their evolution through the course of an eruption, or the effect of conduit shape on rates of magma ascent. We propose to analyze conduit evolution during the 1992 eruptions of Mt. Spurr, Alaska, by using individual earthquakes to determine the stress field around the conduit for different phases of the eruptive sequence. This work will both complement and test results from the numerous seismic and petrologic studies already completed on the Spurr eruptive sequence. We are particularly interested in determining the stress state of the conduit during (1) the ten months of activity leading up to the first explosive event, (2) the intra-eruptive period [June - September 1992], and (3) the post-eruptive period. Evaluation of these three time periods will allow us to evaluate conditions of magma ascent prior to eruptive activity, examine the response of the conduit to individual eruptions, and test the hypothesis that seismic swarms in November and December of 1992 were actually eruptions that "failed" because a solidified plug had formed at shallow levels. Our results will thus both provide insight into the 1992 eruptions at Mt. Spurr and aid development of a general model of stress field response to episodes of magma migration. Additionally, we will compare our results with those from a stress field study of dike emplacement at nearby Iliamna Volcano with the hope of shedding light on conditions that either promote or hinder propagation of intruding magma to the surface, thus improving interpretations of future seismic crises in volcanic regions.