Constraining Transcrustal Magmatic Systems with Receiver Functions Along the Aleutian Island Arc

火山下面的地下管道系统仍然没有得到很好的了解。最近对地壳岩浆储存的了解表明，它们是由熔体和晶体混合物组成的复杂的多层系统。然而，目前尚不清楚岩浆是如何从地幔通过火山弧储存和运输到地壳的。火山弧是位于俯冲构造板块之上的火山链，也就是说，一个板块潜入另一个板块之下。弧型火山的岩浆系统是连接俯冲板块和为火山喷发提供岩浆的浅层岩浆储层的关键环节。然而，许多现有的限制岩浆储存深度的方法在中深部地壳中分辨率相对较低。接收函数是一种在火山环境中相对未得到充分利用的地震成像技术。他们最近在描绘地壳深处岩浆储存的能力上显示出了希望。在这里，研究人员应用这项技术对阿拉斯加阿留申岛弧火山下的岩浆系统进行了成像。利用最先进的地震分析，他们逐渐揭示了火山管道系统的复杂性。这项研究还有助于开发一种成像技术，这种技术可以应用于全球其他火山。该项目的成果改善了阿拉斯加的火山危害评估，那里的火山喷发威胁着当地居民和空中交通。事实上，它的主要目标火山被国家火山预警系统列为最高优先级或高优先级监测。该项目还为一名早期职业女性科学家提供支持。它为夏威夷大学的研究生和本科生提供火山地震学方面的培训。该项目由地球物理学计划和促进竞争性研究的既定计划（EPSCoR）共同资助。在这里，研究人员对地震数据进行了新颖的接收函数分析，以约束沿着阿留申岛弧的火山样带下的地壳岩浆结构。他们利用现有的宽带数据计算P-to-s接收函数，以确定地壳地震速度模型，该模型在地壳中至深部（深度≥10公里）具有主要敏感性。他们集中研究了阿留申群岛的六座火山——奥克莫克火山、马库申火山、阿库坦火山、韦斯特达尔火山、帕夫洛夫火山和希沙尔丁火山，并结合了此前克利夫兰火山的研究结果。接收函数很适合探测地壳中的低速区，这可以指示岩浆的储存。该样带对板块深度、水含量、火山地震活动分布和覆盖地壳性质的变化进行了采样；这些因素被假设与弧型火山下岩浆储存和运输的变化有关。该团队还计算了西阿留申群岛（Gareloi, Tanaga, Kanaga, Great Sitkin, Korovin）次级样带的接收函数；虽然可获得的数据明显减少，但这为未来在阿拉斯加-阿留申弧上扩展该技术奠定了基础。该项目为火山下地壳岩浆储存的深度和结构提供了新的限制。它使研究沿弧的火山活动变化的来源成为可能。通过与阿拉斯加火山观测站（AVO）的合作，该团队利用这些结果来确定阿留申群岛未来的监测和研究需求。该奖项反映了美国国家科学基金会的法定使命，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。

The subterranean plumbing system beneath volcanoes is still not well understood. Recent advances in the understanding of crustal magmatic storage reveal them as complex, multi-layered systems consisting of both melt and crystal mush. However, it remains unclear how magma is stored and transported from the Earth’s mantle through the crust at volcanic arcs. A volcanic arc is a chain of volcanoes located above a subducting tectonic plate, i.e., a plate diving underneath another. Magmatic systems at arc volcanoes are a critical link between the subducting slab and the shallow magma reservoirs that feed volcanic eruptions. However, many established methods of constraining depth of magma storage have relatively low resolution in the mid-to-deep crust. Receiver functions are a technique of seismic imaging relatively underutilized in volcanic settings. They have recently shown promise in their ability to image magma storage in the deep crust. Here, the researchers apply this technique to image the magmatic system beneath volcanoes in the Aleutian Island arc, in Alaska. Using state-of-the-art seismic analysis, they gradually unveil the complexity of volcanoes’ plumbing system. This study also contributes to developing an imaging technique that can be applied to other volcanoes around the Globe. The project’s outcomes improve volcanic hazard assessment in Alaska where eruptions threaten local populations and air traffic. Indeed, its primary target volcanoes are classified as Highest Priority or High Priority for monitoring by the National Volcano Early Warning System. The project also provides support for an early-career female scientist. It fosters training in volcano seismology to graduate and undergraduate students at University of Hawaii. This project is jointly funded by the Geophysics program, and the Established Program to Stimulate Competitive Research (EPSCoR).Here, the researchers conduct novel receiver function analysis of seismic data to constrain the crustal magmatic structure beneath a transect of volcanoes along the Aleutian Island arc. They calculate P-to-s receiver functions using existing broadband data to determine crustal seismic velocity models with primary sensitivity in the mid- to deep-crust (≥ 10 km depth). They focus on six Aleutian volcanoes - Okmok, Makushin, Akutan, Westdahl, Pavlof, and Shishaldin - and incorporate previous results from Cleveland Volcano. Receiver functions are well suited to detect low velocity regions in the crust, which can indicate magma storage. This transect samples variations in depth to slab, H2O content, volcanic seismicity distribution, and overriding crustal properties; these factors have been hypothesized to relate to variations in magmatic storage and transport beneath arc volcanoes. The team also calculate receiver functions along a secondary transect in the Western Aleutians (Gareloi, Tanaga, Kanaga, Great Sitkin, Korovin); while significantly less data is available, this gives a basis for future expansion of the technique across the Alaska-Aleutian arc. This project provides new constraints on the depths and structure of magmatic storage throughout the crust beneath the volcanoes. It enables investigation into the sources of variation in volcanic behavior along arcs. Through collaboration with the Alaska Volcano Observatory (AVO), the team utilizes these results to identify future monitoring and research needs in the Aleutians.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.