Cyclic ground tilt associated with the 2004–2008 eruption of Mount St. Helens
Cyclic ground tilt associated with the 2004–2008 eruption of Mount St. Helens
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与 2004-2008 年圣海伦斯火山喷发相关的周期性地面倾斜
DOI：
10.1029/2009jb007102
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发表时间：
2010
影响因子：
--
通讯作者：
P. Segall
中科院分区：
文献类型：
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作者：
K. Anderson;M. Lisowski;P. Segall
[1]2004-2008年圣海伦斯火山喷发的长期行为的特点是地震活动，圆顶增长和大规模地面变形的速率逐渐下降，但在几分钟的时间尺度上，浅层近周期性的“鼓声”地震表明了短暂的行为。为了更好地描述这种行为和任何相关的地面变形，安装了倾斜仪网络，并记录了火山口内数千次周期性倾斜事件。这些事件的持续时间从几分钟到几小时不等，对于它们来说太长了，不可能是由鼓声地震活动直接引起的。火山活动的特点是一个可恢复的，不对称的模式，快速倾斜远离喷口，然后是一个更渐进的逆转，是高度相关的不同的倾斜仪在火山口，有时发生在与火山地震活动，并停止在喷发结束。倾斜矢量集中在先前存在的20世纪80年代熔岩圆顶中心以南的一个点上，并且火山口外部没有可检测到的倾斜，这表明来源较浅（<1公里）。我们研究了几种模型，包括管道加压和塞子滑动或气体损失和粘滑行为之间的接口上升的塞子和20世纪80年代的熔岩圆顶的周期。陨石坑内的站的数量少，防止源类型或几何形状的独特的确定，但结果是一致的机制，涉及挤压的半固体英安岩塞和/或循环导管加压。
[1] The long-term behavior of the 2004–2008 effusive eruption of Mount St. Helens was characterized by a gradual decline in the rates of seismicity, dome growth, and broad-scale ground deformation, but shallow near-periodic “drumbeat” earthquakes over timescales of minutes indicated episodic short-term behavior. In part to better characterize this behavior and any associated ground deformation, a network of tiltmeters was installed and recorded thousands of cyclic tilt events within the crater. The duration of these events, from minutes to hours, was too long for them to be directly caused by the drumbeat seismicity. Tilt events were characterized by a recoverable, asymmetric pattern of rapid tilt away from the vent followed by a more gradual reversal, were highly correlated between different tiltmeters in the crater, sometimes occurred in association with volcanic seismicity, and ceased at the end of the eruption. Tilt vectors converged on a point just south of the center of the preexisting 1980s lava dome, and the absence of detectable tilt outside the crater suggests a shallow source (<1 km). We examine several models, including cycles of conduit pressurization and plug slip or gas loss and stick-slip behavior on the interface between the ascending plug and the 1980s lava dome. The small number of stations within the crater prevents a unique determination of source type or geometry, but results are consistent with a mechanism involving extrusion of the semisolid dacite plug and/or cycles of conduit pressurization.