Collaborative Research: An integrated seismic-geodetic study of active magmatic processes at Sierra Negra volcano, Galapagos Islands

智慧价值海洋岛屿火山的起源和发展需要105到106年的时间，需要一个长期的岩浆管道系统来将岩浆从地幔输送到地表。然而，只有一小部分岩浆喷发；岩浆储存在地壳岩浆室中，或被困在壳幔边界附近。这些岩浆侵入使地壳生长，并改变应力状态。伴随岩浆侵入而来的压力增加使火山建筑膨胀，引发地震和喷发。因此，岩浆室和管道的几何形状是开发火山变形和喷发预测模型的基础。我们的综合地震和大地测量数据采集和建模项目旨在成像世界上变形最快的热点火山系统--加拉帕戈斯群岛的内格拉火山--之下的岩浆管道系统。现有的合成孔径雷达数据提供了大范围地表变形的高分辨率图像，而GPS提供了垂直和水平变形的连续时间序列。然而，如果没有关于地震应变分布和机制以及地壳和上地幔结构的补充地震信息，我们就不能区分玄武岩火山生长模式。我们将部署和维护16台宽带地震仪，为期两年，记录本地和远程地震的地震波，以阐明塞拉内格拉火山下岩石圈内的岩浆管道系统和应力状态，以了解浅层岩浆侵入、挤压和火山口内断裂过程之间的应力相互作用。预期的结果是一个新的内格拉-S浅部和深部岩浆系统的4D模型，该模型满足地震和大地测量的要求，并受到地震位置、震源机制、波速和环境噪声层析成像、地震各向异性、基床和莫霍面深度的接收函数估计以及现有岩石学数据的约束。我们将确定火山内部和周围响应岩浆侵入和撤退的应力随时间变化的状态，包括陷门断层作用和岩浆侵入之间的动态关系。然而，只有一小部分岩浆喷发；岩浆储存在地壳岩浆室中，或被困在壳幔边界附近。这些岩浆侵入使地壳生长，并改变应力状态。伴随岩浆侵入而来的压力增加使火山建筑膨胀，引发地震和喷发。加拉帕戈斯群岛的塞拉·内格拉火山是这些海洋岛屿火山中变形最快的。对地震和地表形变的持续监测对于推断岩浆室和管道的几何形状以及火山建筑物本身的物理变化至关重要。这些数据反过来为世界范围内的火山变形和喷发提供预测模型。我们的持续地震、卫星、GPS监测和建模项目旨在最大化更广泛的影响，这些影响分为3个领域：火山灾害、教育和国际合作。近100万人生活在活动的玄武岩火山上；了解岩浆供应、应力状态和喷发之间的关系对于危险评估至关重要，包括潜在的引发海啸的侧翼不稳定性。大地测量和地震监测提供的基线对于在加拉帕戈斯群岛和世界各地的其他玄武岩火山制定火山灾害减灾计划至关重要。该项目将为美国本科生、研究生和厄瓜多尔学生提供一个合作机会。来自两国的学生将从实地地球物理的现实中受益，获得宝贵的地震学和大地测量学技能，这些技能可以转化为工作场所或高级学位课程。这项工作由地球物理和地球化学项目以及国际科学和工程办公室的美洲项目共同资助。

Intellectual MeritsOcean island volcanoes initiate and grow over time periods of 105 to 106 years, requiring a long-lived magmatic plumbing system to transport magma from the mantle to the surface. Only a fraction of the magma, however, is erupted; magma is stored in crustal magma chambers, or trapped near the crust-mantle boundary. These magma intrusions grow the crust, and change the state of stress. The increase in pressure accompanying magma intrusion inflates the volcanic edifice, triggering earthquakes and eruptions. The geometry of the magma chambers and conduits, therefore, is fundamental to the development of predictive models of volcano deformation and eruption.Our integrated seismic and geodetic data acquisition and modelling project aims to image the magma plumbing system beneath the most rapidly deforming hotspot volcano system in the world: Sierra Negra volcano in the Galapagos Archipelago. Existing SAR data provide high-resolution images of surface deformation over broad regions, and GPS provides continuous time series of vertical and horizontal deformation. We cannot, however, differentiate between the basaltic volcano growth models without complementary seismic information on the distribution and mechanisms of seismic strain, as well as the crust and upper mantle structure. We will deploy and maintain 16 broadband seismometers for two years, recording seismic waves from local and distant earthquakes to illuminate the magmatic plumbing system and state of stress within the lithosphere beneath Sierra Negra volcano to understand the stress interaction between shallow magma intrusion, extrusion, and intra-caldera faulting processes. The anticipated results are a new 4D model of Sierra Negra?s shallow and deep magmatic system that satisfies seismic and geodetic observations, and is constrained by earthquake locations, focal mechanisms, wavespeed and ambient noise tomography, seismic anisotropy, receiver function estimates of sill and Moho depths, and existing petrological data. We will determine the time-varying state of stress within and around the volcano in response to magma intrusion and withdrawal, including the dynamic relationship between trapdoor faulting and magma intrusionBroader Significance and ImportanceOcean island volcanoes initiate and grow over time periods of 105 to 106 years, requiring a long-lived magmatic plumbing system to transport magma from the mantle to the surface. Only a fraction of the magma, however, is erupted; magma is stored in crustal magma chambers, or trapped near the crust-mantle boundary. These magma intrusions grow the crust, and change the state of stress. The increase in pressure accompanying magma intrusion inflates the volcanic edifice, triggering earthquakes and eruptions. Sierra Negra volcano in the Galapagos Archipelago is the most rapidly deforming of these ocean island volcanoes. Continuous monitoring of earthquake and surface deformation is vital to deduce the geometry of the magma chambers and conduits, and the physical changes to the volcano edifice itself. These data, in turn, inform predictive models of volcano deformation and eruption worldwide.Our continuous seismic, satellite, GPS monitoring and modeling project has been designed to maximize the broader impacts, which fall into 3 areas: volcanic hazards, education, and international collaboration. Nearly a million people live on active basaltic volcanoes; understanding the relationship between magma supply, state of stress and eruptions is vital for hazard assessment, including the potential for tsunami-generating flank instabilities. The baseline provided by the geodetic and seismic monitoring is essential to development of a volcanic hazard mitigation program in the Galápagos Archipelago, and other basaltic volcanoes worldwide.This project will provide a collaborative opportunity for US undergraduate, graduate, and Ecuadorian students. Students from both countries will benefit from experience with the realities of field-based geophysics, gaining valuable skills in seismology and geodesy that can be translated to the workplace or advanced degree programs.This work is co-funded by the Geophysics and Geochemistry Programs and the Americas Program of the Office of International Science and Engineering.