Magmatic system structure and seismicity of the Three Sisters volcanic complex

本项目调查了位于俄勒冈州中部的三姐妹篇火山群。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的基本过程的了解。这个火山系统是活跃的，附近的人口中心的存在意味着三姐妹篇被归类为美国的一个非常高的威胁火山系统。三姐妹篇火山复合体包括各种各样的火山结构和地质上年轻的熔岩（约2,000年）。此外，大约20年的卫星数据显示，火山附近的地区由于地表下的膨胀而变形。现有的数据很少，部分原因是火山附近是一个难以进入的联邦保护荒野。该项目将通过使用小型临时地震仪器增加对这些地区的观测，这些仪器可以步行运输，不需要挖掘，以解决无障碍方面的挑战和尽量减少影响的需要。将新的临时地震数据与现代成像和地震探测方法相结合，研究人员将获得地下结构的系统视图。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。地震数据收集和分析将吸引来自多个机构的学生和来自区域灾害监测机构的人员，以促进专业培训和与利益相关者的沟通。三姐妹篇火山群被美国地质调查报告列为非常高的威胁系统，大地测量证据表明正在进行的地表变形，熔岩流年轻约1,600年，全新世喷发的成分从玄武安山岩到流纹岩。然而，很少有知识的3-D分布的中上地壳岩浆储存和微震活动下，这个多喷口火山复杂的高瀑布地堑内。观测地震学一直受到限制，需要在一个大的联邦荒野的影响最小。该项目将部署一组低影响节点地震仪，以提供三个姐妹篇岩浆系统的第一次局部成像。分析的数据将促进了解如何在多喷口系统的岩浆库结构是链接到空间变化的建筑和喷发的成分，主要是玄武安山岩在北方的火山复合体过渡到更普遍的流纹岩喷发在南端。利用新的临时网络数据的地震成像将开始于相对常规的环境噪声表面波层析成像，然后通过应用各向异性伴随层析成像来推进临时节点阵列成像的边界。利用数值三维波传播和反演方法，检验了沉积物地形和径向各向异性对岩浆储层成像的影响。新的数据还将被用于审查微震活动和进行局部界面的接收器功能成像，这可以更好地定义构造和岩浆变形结构之间的相互作用。该奖项反映了NSF的法定使命，并被认为值得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来支持。

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.