Physics-Based Volcano Geodesy with Application to Effusive Eruptions at Mount St Helens

在火山爆发之前，岩浆聚集在地球上的浅水库中？的外壳。 因此，压力增加，在这些岩浆房，变形或？膨胀？地球？相比之下，在喷发期间，岩浆离开这些水库，减少压力，导致地球？表面是什么？泄气？ 更好地了解这些信号有助于改善社会对火山爆发的反应，例如可能的疏散和改变火山附近的航线，就像2010年冰岛火山爆发后一样。该项目正在开发新的基于物理学的火山变形模型，该模型可与地球镜板块边界的变形测量相结合，以改进对喷发持续时间和可能喷发的物质量的预测。 该项目正在研究一种数据同化方法，其中使用可用数据来开发描述岩浆系统状态的参数的概率估计。 然后，这些被用来初始化预测未来行为的前向模型的集合，包括喷发持续时间和总喷发量。 鉴于改进的正演模型，这种方法具有与现有数据和现实的基于物理的喷发模型相一致的优点。 基于物理的火山喷发预报在概念上类似于将卫星和其他数据纳入复杂天气模型的数值天气预报。技术摘要本项目采用马尔可夫链蒙特卡罗（MCMC）反演连续GPS位置，岩浆流出，和其他数据使用基于物理的前向模型的喷发。 包括一个物理上一致的喷发模型允许的估计程序，以约束参数的利益，不能解决的传统方法，包括地壳岩浆房的体积和初始含水量的岩浆。 这些参数影响到喷发的规模和潜在的爆炸潜力。正在进行的工作是增加现实主义的正演模型，包括：1）平衡结晶的岩浆，因为它上升和压力下降; 2）明确考虑从分布式粘性流的流变学过渡到固体活塞流与边界断层上的滑动，基于宾汉流体模型和3）明确考虑气体损失（H2O和CO2）通过横向和垂直扩散。 其他目标包括更好的喷发开始和停止模型。该方法正在应用于2004-2008年圣海伦斯火山形成圆顶的喷发，包括来自板块边界观测站的全球定位系统数据，并可应用于其他火山，包括阿拉斯加的奥古斯丁、日本的云仙和蒙特塞拉特的苏弗里埃山。

Non-technical summaryPrior to volcanic eruptions magma accumulates in shallow reservoirs in Earth?s crust. As a result, pressure increases in these magma chambers, which deforms or ?inflates? the Earth?s surface; in contrast, during eruptions, magma leaves these reservoirs, decreasing pressure and causing the Earth?s surface to ?deflate?. Better understanding of these signals could help improve societal responses to volcanic eruptions, such as possible evacuations and changes to airline routes near volcanoes like following the 2010 Icelandic eruption. This project is developing new physics-based models of volcano deformation, which can be coupled with deformation measurements from the EarthScope Plate Boundary to improve forecasts of the duration of an eruption and the volume of material that may be erupted. The project is investigating a data assimilation approach in which available data are used to develop probabilistic estimates for parameters that describe the state of the magmatic system. These are then used to initialize an ensemble of forward models that predict future behavior, including eruption duration and total erupted volume. Given improved forward models, this approach has the advantage of being consistent with both available data and realistic physics-based eruption models. Physics-based volcano eruption forecasts are similar in concept to numerical weather forecasts that assimilate satellite and other data into sophisticated weather models. Technical summaryThis project employs Markov Chain Monte Carlo (MCMC) inversion of continuous GPS positions, magma efflux, and other data using a physics-based forward model of an effusive eruption. Including a physically consistent eruption model allows the estimation procedure to constrain parameters of interest that are not resolved by traditional approaches, including the volume of the crustal magma chamber and the initial water content of the magma. These parameters influence the size and potential explosive potential of eruptions. Ongoing work is increasing the realism of the forward model by including: 1) equilibrium crystallization of the magma as it ascends and pressure decreases; 2) explicit consideration of the rheological transition from distributed viscous flow to solid plug flow with slip on bounding faults, based on a Bingham fluid model and 3) explicit consideration of gas loss (both H2O and CO2) through both lateral and vertical diffusion. Other goals include better models of the eruption onset and cessation. The method is being applied to the 2004-2008 dome forming eruption of Mount St. Helens (MSH), including GPS data from the Plate Boundary Observatory (PBO) and could be applied to other volcanoes, including Augustine in Alaska, Unzen in Japan, and the Soufriere Hills on Montserrat.