Controls on explosive basaltic eruptions within the San Francisco Volcanic Field: Constraints from seismic imaging and multiphase magma ascent modeling

对旧金山火山场内爆炸性玄武岩喷发的控制：地震成像和多相岩浆上升模型的限制

• 批准号: 2202666
• 负责人: Eric Kiser
• 金额: $ 74.91万
• 依托单位: University of Arizona
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-09-01 至 2025-08-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2202666&HistoricalAwards=false
• 关键词: Controls; explosive; basaltic; eruptions; within

Volcanic eruptions are major hazards that can cause significant socio-economic effects on local populations and short-term changes to the climate that have a global impact. Many eruptions are fed by a single conduit that brings magma to the surface repeatedly over time producing major volcanic edifices associated with volcanic arcs around the world. In contrast, volcanic fields are composed of tens to hundreds of volcanic vents that are distributed over areas of 100 to 100,000 km2. These vents typically only produce a single eruption before becoming inactive and the locations of subsequent eruptions can be unpredictable and at significant distances from the previous events. Furthermore, the eruption styles within these volcanic fields can vary between non-explosive lava flows to violently explosive events that eject volcanic ash and gases tens of kilometers into the atmosphere. The San Francisco Volcanic Field (SFVF) in Northern Arizona exhibits these classic characteristics of a volcanic field and includes one of the best documented examples of an explosive eruption within these settings at Sunset Crater northeast of Flagstaff, AZ. The distribution of volcanic vents in the SFVF and why significant variability exists in the eruption styles of the volcanic field remain poorly understood. This is not only the case for the SFVF, but for every volcanic field on Earth, making it difficult to understand potential hazards these systems represent to local populations. This project seeks to better understand this system by combining seismological and eruption modeling approaches. Hundreds of instruments used for measuring ground motion (seismometers) will be installed throughout the SFVF in order to detect signals from local earthquakes. This seismological component of the project will be complemented by the development of computer models that simulate volcanic eruptions. In addition to exploring the general conditions necessary for producing non-explosive and explosive eruptions in volcanic fields, this component of the project will use the details of magma distribution beneath Sunset Crater derived from the seismological work, to constrain the specific conditions that led to this eruption. This will be the first project of its kind to produce a detailed image of the magmatic system beneath an entire volcanic field and directly use these constraints to improve eruption modeling. The work will improve hazard assessment for local populations (e.g., Flagstaff, AZ), as well as for population centers near other volcanic fields around the world (e.g., Auckland, New Zealand). Students from Chandler-Gilbert Community College in Arizona will participate in the research for this project and will be recruited to come to the University of Arizona following completion of their 2-year degrees. Teaching modules related to volcanic hazards will also be produced from this project and distributed to the broader academic community.The San Francisco Volcanic Field (SFVF) covers an area approximately 5,000 km2 in northern Arizona and includes nearly 600 basaltic vents interspersed with a few, large-volume intermediate to silicic volcanic centers. Over the past ~5-6 Myr, the locus of volcanism at the SFVF has migrated eastward at a rate of 1-3 cm/yr with the 1085 CE eruption that produced Sunset Crater being the youngest in this volcanic field. Though most of the volcanic vents within the SFVF exhibit landforms common to the effusive eruption styles of distributed volcanic fields, the Sunset Crater eruption was violently explosive and significantly affected the indigenous population living in the region at the time. Key to improving our understanding of the hazards of the SFVF is better constraining the conditions that led to the sub-Plinian style eruption at Sunset Crater which did not affect nearby volcanic vents. Existing studies have indicated that a mid-crustal magma storage zone played a key role in the Sunset Crater eruption, however, currently our understanding is limited regarding how the properties of this storage zone (e.g., size, depth, melt fraction, volatile content) influenced the eruption. Details of the crustal magma storage system that have resulted in differing volcanic compositions (mafic vs. felsic) within the SFVF are also unknown. By integrating seismic imaging and eruption modeling, this project lays out a holistic approach to better understand the subsurface magmatic plumbing system and processes that drive volcanic activity within the SFVF. Specific components of this project will include (1) detailed characterization of seismicity and the development of high-resolution 3D seismic velocity models of the crust beneath the SFVF to image current and past magmatic systems associated with this volcanic field, (2) the development of coupled magma chamber pressurization and multiphase magma ascent models to determine the conditions necessary to drive effusive to explosive basaltic eruption styles, and (3) combining constraints from seismic imaging work on the volumes and depths of crustal magma reservoirs with these state-of-the-art eruption models to better understand the subsurface processes that drove the violently explosive Sunset Crater eruption.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.

火山喷发是重大灾害，可能对当地居民造成重大社会经济影响，并对气候造成短期变化，从而产生全球影响。许多火山喷发都是由单一管道供给的，随着时间的推移，该管道反复将岩浆带到地表，形成与世界各地火山弧相关的主要火山建筑物。 相比之下，火山田由数十到数百个火山喷口组成，分布在100到100,000平方公里的面积上。这些喷口在变得不活跃之前通常只会产生一次喷发，并且后续喷发的位置可能无法预测，并且与之前的事件相距很远。此外，这些火山区内的喷发方式也各不相同，从非爆炸性熔岩流到将火山灰和气体喷射到大气中数十公里的剧烈爆炸事件。 亚利桑那州北部的旧金山火山场 (SFVF) 展现了火山场的这些经典特征，并且包括亚利桑那州弗拉格斯塔夫东北部日落火山口的这些环境中爆发性喷发的最有记录的例子之一。 SFVF 中火山喷口的分布以及火山场喷发方式为何存在显着变化的原因仍然知之甚少。不仅 SFVF 如此，地球上的每个火山场也是如此，因此很难了解这些系统对当地居民造成的潜在危害。 该项目旨在通过结合地震学和喷发建模方法来更好地了解该系统。整个 SFVF 将安装数百台用于测量地面运动的仪器（地震仪），以检测当地地震的信号。该项目的地震学部分将通过模拟火山喷发的计算机模型的开发得到补充。除了探索火山场中产生非爆炸性和爆炸性喷发所需的一般条件外，该项目的这一部分还将利用从地震工作中获得的日落火山口下方岩浆分布的详细信息，来约束导致这种喷发的具体条件。爆发。 这将是同类项目中第一个生成整个火山场下方岩浆系统的详细图像并直接使用这些约束来改进喷发建模的项目。这项工作将改善对当地居民（例如亚利桑那州弗拉格斯塔夫）以及世界各地其他火山区附近的人口中心（例如新西兰奥克兰）的危害评估。 亚利桑那州钱德勒-吉尔伯特社区学院的学生将参与该项目的研究，并在完成两年学位后被招募到亚利桑那大学学习。该项目还将制作与火山灾害相关的教学模块，并分发给更广泛的学术界。旧金山火山场 (SFVF) 覆盖亚利桑那州北部约 5,000 平方公里的面积，包括近 600 个玄武岩喷口，其中散布着一些大型喷口。 -体积中等至硅质火山中心。 在过去约 5-6 Myr 中，SFVF 的火山活动轨迹以每年 1-3 厘米的速度向东迁移，公元 1085 年的喷发产生了日落火山口，成为该火山区中最年轻的火山口。尽管 SFVF 内的大多数火山喷口呈现出与分布式火山场的喷发样式相同的地貌，但日落火山口的喷发却非常剧烈，对当时居住在该地区的土著居民产生了重大影响。提高我们对 SFVF 危害的了解的关键是更好地限制导致日落火山口亚普林尼式喷发的条件，该喷发不会影响附近的火山喷口。 现有研究表明，中地壳岩浆储存区在日落火山口喷发中发挥了关键作用，然而，目前我们对该储存区的性质（例如大小、深度、熔体分数、挥发物含量）的了解有限。影响了喷发。导致 SFVF 内不同火山成分（镁铁质与长英质）的地壳岩浆储存系统的细节也是未知的。通过整合地震成像和喷发建模，该项目提出了一种整体方法，以更好地了解地下岩浆管道系统和驱动 SFVF 内火山活动的过程。该项目的具体组成部分将包括 (1) 地震活动的详细表征以及 SFVF 下地壳高分辨率 3D 地震速度模型的开发，以对与该火山场相关的当前和过去的岩浆系统进行成像，(2) 开发耦合岩浆室加压和多相岩浆上升模型，以确定驱动喷发型玄武岩喷发类型所需的条件，以及（3）结合地震成像工作对玄武岩体积和深度的约束地壳岩浆库与这些最先进的喷发模型，以更好地了解驱动日落火山口喷发剧烈爆炸的地下过程。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力优点和技术进行评估，被认为值得支持。更广泛的影响审查标准。