Magmatic system structure and seismicity of the Three Sisters volcanic complex

三姐妹火山杂岩岩浆系统结构与地震活动

• 批准号: 2342525
• 负责人: Brandon Schmandt
• 金额: $ 39.97万
• 依托单位: University of New Mexico
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2024
• 资助国家: 美国
• 起止时间: 2024-06-01 至 2027-05-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2342525&HistoricalAwards=false
• 关键词: Magmatic; system; structure; seismicity; Three

This project investigates the Three Sisters volcanic complex in central Oregon. It will use seismic observations and methods to advance understanding of volcanic hazards and the fundamental processes that create different types of volcanoes and magma types. This volcanic system is active, and the presence of nearby population centers means the Three Sisters is classified as a Very High Threat volcanic system for the U.S. The Three Sisters volcanic complex includes a wide variety of volcanic structures and geologically young lavas (about 2,000 years old). Additionally, about two decades of satellite data show that areas near the volcanoes are deforming due to inflation under the surface. Existing data are scarce partly because the immediate vicinity of the volcanoes is a difficult to access and federally protected Wilderness. This project will add observations in these areas by using small temporary seismic instruments, that can be transported on foot and do not require digging, to address both the accessibility challenges and the need for minimal impact. Combining the new temporary seismic data with modern imaging and earthquake detection methods, the researchers will gain a systematic view of subsurface structures. This will assist in more rigorously understanding the record of prior eruptions and ongoing monitoring of deformation. The seismic data collection and analysis will engage students from multiple institutions and personnel from regional hazard monitoring agencies to promote professional training and communication to stakeholders.The Three Sisters volcanic complex is classified by a U.S. Geologic Survey report as a Very High Threat system, with geodetic evidence for ongoing surface deformation, lava flows as young as about 1,600 years, and Holocene eruptions of compositions ranging from basaltic andesite to rhyolite. Yet, there is little knowledge of the 3-D distribution of middle to upper crustal magma storage and microseismicity beneath this multi-vent volcanic complex located within the High Cascades graben. Observational seismology has been limited by the need for minimal impact in a large federal Wilderness. The project will deploy an array of low-impact nodal seismometers to provide the first local imaging of the Three Sisters magmatic system. Analysis of the data will advance understanding of how magma reservoir structure in multi-vent systems is linked to spatial variations in edifice construction and erupted compositions, with dominantly basaltic andesite in the northern part of the volcanic complex transitioning to more prevalent rhyolite eruptions at the southern end. Seismic imaging with the new temporary network data will begin with relatively conventional ambient noise surface wave tomography and then push the boundaries of temporary nodal array imaging by applying anisotropic adjoint tomography. The influences of edifice topography and radial anisotropy on magma reservoir imaging will be tested with numerical 3-D wave propagation and inversion methods. The new data will also be used to scrutinize microseismic activity and conduct receiver function imaging of localized interfaces, which could better define interactions between tectonic and magmatic deformation structures.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.

该项目调查了俄勒冈州中部的三姐妹火山综合体。它将利用地震观测和方法来促进对火山灾害和产生不同类型火山和岩浆类型的基本过程的了解。这个火山系统是活跃的，附近人口中心的存在意味着三姐妹火山系统被归类为美国的极高威胁火山系统。三姐妹火山杂岩包括各种各样的火山结构和地质上年轻的熔岩(大约2000年)。此外，大约20年的卫星数据显示，由于地表下的通货膨胀，火山附近的地区正在变形。现有数据很少，部分原因是火山附近很难进入，而且受到联邦政府的保护。该项目将通过使用小型临时地震仪器在这些地区增加观测，这些仪器可以徒步运输，不需要挖掘，以解决无障碍和影响最小的需要。将新的临时地震数据与现代成像和地震探测方法相结合，研究人员将对地下结构有一个系统的了解。这将有助于更严格地了解以前喷发的记录和对变形的持续监测。地震数据的收集和分析将让来自多个机构的学生和地区灾害监测机构的人员参与，以促进专业培训和与利益相关者的交流。美国地质调查局报告将三姐妹火山综合体归类为极高威胁系统，有大地测量证据表明持续的地表变形，熔岩流动，从玄武岩安山岩到流纹岩的全新世喷发。然而，对于位于高瀑布地块内的这个多喷口火山杂岩之下的中上地壳岩浆储量和微震活动的三维分布知之甚少。观测地震学由于需要在大范围的联邦荒野中产生最小的影响而受到限制。该项目将部署一组低影响的结点地震仪，以提供三姐妹岩浆系统的第一次局部成像。对数据的分析将促进对多喷口系统中的岩浆库结构如何与建筑物结构和喷发成分的空间变化有关的理解，火山杂岩北部的主要玄武岩安山岩在南端过渡到更普遍的流纹岩喷发。利用新的临时网络数据进行地震成像将从相对常规的环境噪声面波层析成像开始，然后通过应用各向异性伴随层析成像来突破临时节点阵列成像的边界。将用数值三维波传播和反演方法测试建筑物地形和径向各向异性对岩浆岩储层成像的影响。新的数据还将用于仔细研究微震活动，并对局部界面进行接收函数成像，这可以更好地定义构造和岩浆变形结构之间的相互作用。这一奖项反映了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，被认为值得支持。