Volcanic eruptions in high resolution

火山地震学主要研究火山爆发前后的时间。虽然火山生命周期中最重要的部分是喷发本身，但在喷发的大爆发阶段，很少有地震被测量到。这是因为测量地震的技术困难，而火山爆发正在产生广泛的地震噪音。 在这里，研究人员通过使用现代地震探测技术来记录大规模爆发期间的地震活动来解决这个问题。他们通过对2008年奥克莫克火山爆发的初步分析来说明新方法;火山破火山口位于阿拉斯加阿留申群岛东部，在没有警告的情况下爆发。多种技术将检测到的事件数量增加了4倍。事件发生率在喷发期间以不平凡的方式变化，其原因尚不清楚。 地震似乎记录了一段与爆炸历史相关但又截然不同的应力和破坏历史。为了更好地限制火山爆发期间的地震率，该团队使用尖端软件重新分析了记录的数据。 经过训练的算法能够在噪声中识别新的地震事件。新的事件目录用于更好地了解火山地下管道系统。同样的方法也适用于阿留申群岛、冰岛和俄罗斯的其他火山，这些火山都表现出类似的大规模喷发。比较研究允许评估火山地震活动性是否可以用来限制地下岩浆循环在大爆发。该项目为一名研究生和一名本科生提供支持和培训，特别是来自科学领域代表性不足的群体。其成果改善了火山灾害评估，有助于减轻当地人口和空中交通的风险。研究人员建议通过利用无监督的全局训练检测算法来改善Okmok的共爆发地震记录。地震率和火山喷发周期之间的关系尚不清楚。不仅在喷发开始时地震率有明显的增加，而且在喷发结束时也出现了地震活动的爆发。 地震活动的增加，在中间的喷发可能与喷发重组，但并不清楚与主要的羽形成事件。这可能是地震对固体地壳中的应力敏感的结果，而不是管道中的喷发过程。利用新记录，研究人员识别并确定了地震的一致震级。新的地震在已知的震级允许一个自我一致的措施，地震率在整个喷发。它可以用来评估地震是否标志着开放最少，压力最大的时间和地点。在项目的第二阶段，同样的方法也适用于其他类似的大规模喷发，这些喷发有足够的、公开的地震数据。这些喷发是：格里姆火山，Kasatochi和Sheveluch。该团队打算与一名本科生一起探索Nabro的数据集，尽管它不太具有可比性。这些比较研究改进了评估地震作为火山开放或关闭状态指标的效用。预期结果将有助于了解加压和打开之间的快速波动是否在重大爆炸性喷发中常见。该奖项反映了NSF的法定使命，并且通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Volcano seismology has focused on the times before and after eruptions. Although the most important part of a volcano’s lifecycle is the eruption itself, few earthquakes have been measured during the large, explosive phase of an eruption. This lack is because of the technical difficulties of measuring earthquakes while the eruption is producing a wide range of seismic noise. Here the researchers address this problem by using modern techniques of earthquake detection to chronicle the seismicity during a large-scale, explosive eruption. They illustrate the new approach with a preliminary analysis of the 2008 eruption of Mount Okmok; the volcano caldera, which exploded without warning, is located in the eastern Aleutian Islands of Alaska. Multiple techniques increase the number of detected events by factor of 4. Event rate varies in a non-trivial way during the eruption which cause is still unclear. Earthquakes appear to be recording a history of stress and failure that is related to, but distinct from the history of explosions. To better constrain earthquake rate during the eruption, the team re-analyzes recorded data using cutting-edge software. The trained algorithm is capable of identifying new seismic events among the noise. The new event catalog is used to better understand the volcano subterranean plumbing system. The same approach is applied to other volcanos in the Aleutians, Iceland, and Russia, which exhibit similar large eruptions. The comparative study allows evaluating whether volcano seismicity can be used to constrain subterranean magma cycle during large eruptions. The project provides support and training for one graduate student and undergraduate students, notably from underrepresented groups in science. Its outcomes improve volcanic hazard assessment, helping mitigating risks for local population and air traffic. The researchers propose to improve the co-eruptive seismic record of Okmok by utilizing an unsupervised, globally trained detection algorithm. The relationship between earthquake rate and the eruption cycle is still unclear. Not only is there an obvious increase in the earthquake rate at the eruption initiation, but there also appears to be a seismicity burst at the end of the eruption. Seismicity increases in the middle of the eruption may be associated with eruption reorganization but is not clearly associated with major plume-forming events. This may be a result of earthquakes’ sensitivity to the stresses in the solid crust rather than the eruptive processes in the conduit. Using the new record, the researchers identify and determine consistent magnitudes for the earthquakes. The new earthquakes at known magnitudes allow a self-consistent measure of earthquake rate throughout the eruption. It can be used to evaluate whether the earthquakes are marking the least open, most pressurized times and places. In the project second phase, the same methods are applied to other similarly large eruptions that have sufficient, publicly available seismic data. Those eruptions are: Grimsvotn, Kasatochi and Sheveluch. The team intends to explore the dataset of Nabro with an undergraduate, although it is not quite comparable. These comparative studies improve assessing the utility of earthquakes as an indicator of opened or closed volcano state. The expected outcomes will help understanding whether rapid fluctuations between pressurization and opening are common in major explosive eruptions.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.