Collaborative Research: Caldera Dynamics and Eruption Cycles at Axial Seamount

火山喷发是塑造地球表面的最重要的过程之一。然而，喷发很难近距离研究，因为它们具有如此大的破坏性。深海海底提供了一个收集火山顶部喷发的详细观察的机会。自2014年以来，NSF海洋天文台计划在距离俄勒冈州海岸300英里的活火山Axial Semona的顶峰火山口南半部分运营了一个有线天文台。2015年，火山喷发，有线仪器的记录提供了许多见解。在这些见解中，包括在预测火山喷发方面的改进。轴向海山正在迅速膨胀，现在预测几年后还会有另一次喷发。这项提议将操作15台用于地震探测的远程海底仪器。在两年的时间里，该项目将寻求记录下一次喷发。这些新的观察将提高对火山中岩浆和裂缝如何相互作用的理解。这种相互作用创造了岩浆进入海底的路径。这项实验是火山科学界发展社区实验的更广泛努力的一部分。这些实验包括不同类型的喷发。通过对不同喷发的比较，科学家们将提高对火山危害的认识。这个项目的数据将向所有公众开放。在科学界，这种数据共享将帮助科学家解释海底火山的地质、热液和生物观测。轴海山是一座海底火山，位于科布热点和胡安德富卡山脊的交汇处，胡安德富卡山脊分别于1998年、2011年和2015年喷发。2015年的喷发是在天文台上线后不久由海洋天文台倡议(OOI)有线阵列上的仪器实时捕捉到的。地球物理观测为喷发预测、火山口环断层的动力学以及熔岩喷发时海底爆炸信号的产生提供了新的见解。然而，由7个台站组成的有线地震台网占地面积小，将分辨率良好的地震地点的空间范围限制在破火山口南部，喷发前的观测持续时间短，使寻找前兆信号变得更加困难。因此，有关北部火山口的动力学、火山口环断层与喷发裂谷的相互作用、喷发旋回岩浆作用对上地壳随时间变化的地震结构的影响以及与更深层次岩浆作用的联系等问题仍有待解决。该项目将在下一次喷发的预测时间窗口内支持为期两年的实地试验，部署15台自主式海底地震仪，以扩大电缆网络的地震覆盖范围，以覆盖整个火山口和南部和北部裂谷的部分地区。开放获取的数据将用于创建地震目录并支持各种研究，以限制整个火山口的动力学，描述喷发岩脉与火山口的相互作用，观察浅层岩浆和构造过程的时空演化，并寻找与更深层次岩浆过程有关的信号。它将解决三个假设：1)与浅层储集层相关的岩浆过程对火山口和裂谷结构起主要控制作用；2)复杂的浅层储集层几何结构反映并影响岩浆运输和储存的演化；3)来自系统深层的岩浆可以被快速动员，并在短时间内(几周/几个月)与浅层储集层相互作用。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，认为值得支持。

Volcanic eruptions are one of the most important processes that shape the Earth’s surface. However, eruptions are difficult to study up close because they are so destructive. The deep seafloor provides an opportunity to collect detailed observations of eruptions immediately atop a volcano. Since 2014, the NSF Ocean Observatories Initiative has operated a cabled observatory in the southern half of the summit caldera of Axial Seamount, an active volcano located 300 miles off the coast of Oregon. In 2015, the volcano erupted and the records from cabled instruments provided many insights. Among these insights were improvements in forecasting eruptions. Axial Seamount is rapidly inflating, and another eruption is now predicted in a few years. This proposal will operate 15 remote seafloor instruments for earthquake detection. Over 2 years the project will seek to record the next eruption. These new observations will improve understanding of how magma and fractures interact in volcanoes. Such interactions create the pathways of magma to the seafloor. This experiment is part of a broader effort in the volcano science community to develop Community Experiments. These experiments include different kinds of eruptions. Through the comparison of the different eruptions scientists will improve the understanding of volcano hazards. The data from this project will be available to all of the public. Among the science community this data sharing will help scientists interpret geological, hydrothermal and biological observations from submarine volcanoes.Axial Seamount is a submarine volcano at the intersection of the Cobb hotspot and the Juan de Fuca ridge that erupted in 1998, 2011 and 2015. The 2015 eruption was captured in real time by the instrumentation on Ocean Observatories Initiative (OOI) Cabled Array shortly after the observatory came online. The geophysical observations yielded new insights into eruption forecasting, the dynamics of caldera ring faults, and the generation of explosive signals on the seafloor as lava erupts. However, the small footprint of the 7-station cabled seismic network limited the spatial extent of well-resolved earthquake locations to the southern portion of the caldera and the short duration of observations prior to the eruption complicated the search for precursory signals. As a result, there are unresolved questions related to the dynamics of the northern caldera, the interactions of the caldera ring faults and eruptive rifts, the impacts of magmatic processes during eruption cycle on the time-dependent seismic structure of the upper crust, and the links to deeper magmatic processes. This project will support a 2-year field experiment in the predicted time window of the next eruption that will deploy 15 autonomous ocean bottom seismographs (OBS) to extend seismic coverage of the cabled network to cover the whole caldera and portions of the south and north rifts. The open access data will be used to create earthquake catalogs and support a variety of studies to constrain the dynamics of the whole caldera, characterize the interaction the eruptive dikes with the caldera, observe the spatiotemporal evolution of shallow magmatic and tectonic process and search for signals associated with deeper magmatic processes. It will address three hypotheses, that: 1) magmatic processes related to the shallow reservoir exert primary control on caldera and rift structure; 2) the complex shallow reservoir geometry reflects and affects the evolution of magma transport and storage; and 3) magma from the deeper part of the system can be rapidly mobilized and interact with the shallow reservoir over short timescales (weeks/months).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.