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

该项目将提高对火山下岩浆储存的认识-这是火山灾害评估的一项关键投入。火山下的岩浆可以用地球物理工具探测到，但火山下的岩浆管道系统的形状仍然未知。 对于危险性分析来说，关键是要知道岩浆中的哪一部分是熔融岩石（熔体），哪一部分是晶体;这个比例控制着岩浆的流动性，从而控制着火山喷发的容易程度。在火山大规模爆发后，地下岩浆系统必须重新组合。为了解析弧火山下再充地壳岩浆管道系统的详细结构，该项目将使用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火山。数据显示，在北方破火山口盆地下方有一个狭窄的破碎岩石柱。在这个构造之下是岩浆系统的最高部分。该项目将进一步分析PROTEUS地震数据，并模拟火山的应力，以便：（一）对火山深处（地壳底部）的岩浆管道系统成像;（二）确定中地壳和上地壳岩浆的熔融含量;（三）探索火山内部结构和区域环境如何控制火山内的岩浆分布。在招收研究生和本科生时，STEM培训的多样性将被优先考虑。该项目将以现有的国际合作为基础，包括与四个不同的欧洲科学机构和前往圣托里尼的国际海洋钻探考察队的合作。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的火山和地震危险评估提供一个框架，圣托里尼的壮观景观每年吸引200多万游客，目前的火山管道系统模型预测垂直广泛的岩浆系统，主要是低熔融分数的晶体泥，在下地壳和中地壳发生分化，岩浆聚集在上地壳。然而，详细的几何形状，分布和整个地壳熔体的组成仍然知之甚少。这些概念模型还预测，在普林尼事件之前，可喷发的熔融物丰富的岩浆房的存在是短暂的。令人感兴趣的是，在火山口形成喷发后，岩浆系统是如何重塑的。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？破火山口塌陷构造和区域应力对岩浆运动的影响。 为了解决在弧火山的再充电地壳岩浆管道系统的详细结构，该项目利用独特的PROTEUS有源地震数据集，从研究圣托里尼火山。这些数据探测了前所未有的波场密度的火山，迄今为止，层析成像分析的第一个到达的P波已经解决了最上层地壳的结构，和周围的火山建筑。结果表明，低速，多孔柱，是狭窄的局限在下面的北方破火山口盆地，下面是上地壳岩浆系统。在这里，PROTEUS地震数据集将被进一步利用来模拟应力状态。拟议的分析将：（一）通过对更深的转向射线和莫霍面反射进行层析成像反演，确定目前已分辨的上地壳储层以下的岩浆系统的结构;（二）通过联合Vp/Vs层析成像和模拟二次到达，更好地限制中地壳和上地壳的熔体含量;（三）从物理特性方面解释地震结果;以及（iv）通过模拟和地震活动性分析，探讨火山内部构造和区域应力如何影响火山内的岩浆聚集。该项目还将建立国际合作，包括四个不同的欧洲机构，并与IODP提案产生协同作用。STEM培训的多样性将在招聘研究生和本科生时优先考虑。这项研究将为圣托里尼的火山和地震危险评估提供一个框架，圣托里尼的壮观景观每年吸引200多万游客。为了最有效地将成果带给公众和当地决策者，该项目利用了希腊合作者和一位科学传播专家。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。

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.