Structure of a recharging crustal magma plumbing system at the Santorini arc volcano

该项目将增进对火山下岩浆储存的了解——这是火山灾害评估的关键输入。可以使用地球物理工具探测火山下方的岩浆，但火山下方岩浆管道系统的形状仍然未知。 对于危险分析，了解岩浆的哪些部分是熔岩（熔体）以及哪些部分是晶体至关重要；这个比率控制着岩浆的流动性，从而控制火山喷发的容易程度。火山发生大规模爆发性喷发后，地下岩浆系统必须重新聚集。为了解析弧火山下方地壳岩浆补给管道系统的详细结构，该项目将使用来自希腊圣托里尼火山的独特地震数据集 PROTEUS。 PROTEUS 数据集以前所未有的细节探测了这座火山。数据揭示了北部破火山口盆地下方狭窄的破碎岩石柱。该结构下方是岩浆系统的最上部。该项目将进一步分析 PROTEUS 地震数据并对火山应力进行建模，以：(i) 对火山深处（地壳底部）的岩浆管道系统进行成像； (ii) 确定位于中地壳和上地壳的岩浆的熔体含量； (iii) 探索火山内部结构如何通过区域环境控制火山内的岩浆分布。在招收研究生和本科生时，将优先考虑 STEM 培训的多样性。该项目将建立在现有的国际合作基础上，包括与四个不同的欧洲科学机构以及圣托里尼国际海洋钻探探险队的合作。为了最有效地将科学成果带给公众和当地决策者，该项目聘请了希腊合作者和科学传播专家。这项研究将为圣托里尼岛的火山和地震灾害评估提供一个框架，那里的壮丽景观每年吸引超过 200 万游客。火山管道系统的当前模型预测垂直广泛的岩浆系统以低熔体分数的晶体糊状物为主，其中下地壳和中地壳发生分异，上地壳发生岩浆堆积。然而，整个地壳中熔体的详细几何形状、分布和成分仍然知之甚少。这些概念模型还预测，在普林尼事件之前，可喷发的富含熔体的岩浆室的存在是短暂的。令人感兴趣的是火山喷发后岩浆系统如何重塑。该项目将解决两个突出的科学问题：（1）弧火山岩浆系统的高分辨率结构是什么以及整个地壳的熔体含量是多少？ (2) 火山口塌陷结构和区域应力如何影响岩浆运动？ 为了解析弧火山地壳岩浆补给管道系统的详细结构，该项目利用来自经过深入研究的圣托里尼火山的独特 PROTEUS 主动源地震数据集。这些数据以前所未有的波场密度探测了火山，迄今为止，对首次到达的纵波的断层扫描分析已经解析了火山大厦及其周围最上层地壳的结构。结果揭示了一个低速多孔柱，该柱被狭窄地限制在北部火山口盆地下方，其下方是上地壳岩浆系统。这里将进一步利用 PROTEUS 地震数据集来模拟应力状态。所提出的分析将：（i）通过更深的转向射线和莫霍面反射的层析反演来确定目前已解析的上地壳储层下方的岩浆系统的结构； (ii) 通过联合 Vp/Vs 层析成像和二次到达模拟，更好地限制中地壳和上地壳的熔体含量； (iii) 根据物理特性解释地震结果； (iv) 通过建模和地震活动分析，探索建筑物的内部结构和区域应力如何影响火山内的岩浆堆积。该项目还将建立国际合作，包括四个不同的欧洲机构以及与 IODP 提案的协同作用。在招收研究生和本科生时，将优先考虑 STEM 培训的多样性。这项研究将为圣托里尼岛的火山和地震灾害评估提供框架，圣托里尼岛的壮丽景观每年吸引超过 200 万游客。为了最有效地将结果带给公众和当地决策者，该项目聘请了希腊合作者和科学传播专家。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

This project will improve the understanding of magma storage under volcanoes - a critical input for volcanic hazard assessments. Magma beneath a volcano can be detected using geophysical tools, but the shape of the magma plumbing systems that underlie volcanoes is still not known. For hazard analyses it is critical to know what fraction of a magma is molten rock (melt) and what fraction are crystals; this ratio controls how fluid the magma is and thus how easy it is for an eruption to occur. After a large, explosive eruption of the volcano, the subsurface magma system has to reassemble. To resolve the detailed structure of a recharging crustal magma plumbing system beneath an arc volcano, this project will use a unique seismic dataset, PROTEUS, from Santorini volcano in Greece. The PROTEUS dataset probed the volcano in unprecedented detail. The data reveal a column of broken rock that is narrowly confined beneath the northern caldera basin. Below this structure lies the uppermost part of the magma system. This project will further analyze the PROTEUS seismic data as well as model the stresses with the volcano to: (i) image the magma plumbing system of the volcano to great depths (the base of the crust); (ii) determine the melt content of magmas located in the mid- and upper-crust; (iii) explore how volcano internal structure and by regional setting control magma distribution within the volcano. When recruiting graduate and undergraduate students, diversity in STEM training will be prioritized. This project will build on existing international collaborations including with four different European scientific institutions and with an International Ocean Drilling expedition to Santorini. To most effectively bring the science results to the public and local decision makers, the project engages Greek collaborators and a science communications expert. This study will provide a framework for volcanic and seismic hazards assessment at Santorini, where the dramatic landscape draws over 2 million tourists per year.Current models of volcano plumbing systems predict vertically extensive magma systems dominated by low melt-fraction crystal mushes where differentiation occurs in the lower and mid crust and magma accumulation in the upper crust. However, the detailed geometry, distribution, and composition of melt throughout the crust remain poorly known. These conceptual models also predict that the existence of eruptible melt-rich magma chambers prior to Plinian events is short-lived. Of interest is how the magma system is reshaped after a caldera-forming eruption. This project will address two outstanding science questions: (1) What is the high-resolution structure of the magmatic system at an arc volcano and what are the melt contents throughout the crust? And (2) How is magma movement affected by caldera collapse structures and regional stresses? To resolve the detailed structure of a recharging crustal magma plumbing system at an arc volcano, this project leverages the unique PROTEUS active-source seismic dataset from the well-studied Santorini volcano. These data probed the volcano with unprecedented wavefield density and, to date, tomographic analysis of first arriving P-waves has resolved the structure of the uppermost crust at, and around, the volcanic edifice. The results reveal a low-velocity, porous column that is narrowly confined beneath the northern caldera basin beneath which is an upper-crustal magma system. Here the PROTEUS seismic dataset will be exploited further to model the stress state. The proposed analyses will: (i) determine the structure of the magmatic system below the currently-resolved upper-crustal reservoir through tomographic inversion of deeper turning rays and Moho reflections; (ii) better constrain the melt content of the mid- and upper- crust through joint Vp/Vs tomography and modeling of secondary arrivals; (iii) interpret the seismic results in terms of physical properties; and (iv) explore how the internal structure of the edifice and regional stresses affect magma accumulation within the volcano through modeling and seismicity analysis. This project will also build international collaborations including four different European institutions and synergies with an IODP proposal. Diversity in STEM training will be prioritized when recruiting graduate and undergraduate students. This study will provide a framework for volcanic and seismic hazards assessment at Santorini, where the dramatic landscape draws over 2 million tourists per year. To most effectively bring the results to the public and local decision makers, the project leverages Greek collaborators and a science communications expert.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.