EAGER: Spatio-temporal Imaging of Mount St. Helens Magmatic System using Efficient Waveform Inversion of Earthquake Records

位于卡斯卡迪亚俯冲带的圣海伦火山是一座活火山，以1980年的毁灭性喷发而闻名，就人命损失和基础设施破坏而言，这场喷发被广泛认为是美国历史上最具灾难性的火山喷发。事实上，美国地质调查局（USGS）认为圣海伦火山是一个非常高的威胁火山。这项计划将照亮圣海伦斯火山岩浆管道系统，帮助科学家更好地预测即将发生的火山活动及其可能的持续时间。这些知识将对减轻火山灾害和帮助拯救人类生命极为有用。该项目是一所大学（科罗拉多矿业学院）和一个政府机构（美国地质勘探局）之间的合作，以扩展尖端技术的应用，该技术最初由一家私营企业（地震科学有限责任公司）开发，用于对油气藏中的水力压裂进行成像，以监测火山系统，从而改善社会。调查人员认为，这种合作将促进碳氢化合物行业和政府实体之间的进一步合作、技术转让和思想交流。在这个项目下开发的过程和技术可能会扩展到其他俯冲带，以帮助图像的巨型逆冲断层和火山系统在世界各地。圣海伦斯火山岩浆系统的结构和时空变化所造成的岩浆生产，运输和存储知之甚少。为了解决这些问题，在过去的三十年里，已经以主动地震勘测和被动记录的形式获得了大量的地震数据，这些数据也是EarthScope计划的一部分。调查人员将利用主动地震数据（包括两个节点地震检波器阵列和PASSCAL得克萨斯地震检波器）和宽频带地震仪的当地地震记录以及主动地震波形数据，利用波形反演生成圣海伦斯火山岩浆系统的高分辨率延时三维图像。这些图像将从浅的上地壳一直延伸到圣海伦斯山下的俯冲板，从而有助于揭示岩浆系统的完整结构，不同岩浆体之间的联系以及岩石的物理状态。圣海伦斯火山岩浆系统的知识（就其结构和时空变化而言）将为一些关键的科学挑战提供有价值的见解，包括地壳演化，地幔中的岩浆生成，从上地幔到浅地壳的岩浆运输，岩浆库的结构和预测火山活动等问题。高分辨率的时空三维图像将特别有助于理解与岩浆侵位/膨胀有关的应力变化，并有助于解释地壳和上地幔中熔体的输送。此外，圣海伦斯火山下地壳和地幔中岩浆的规模、范围和连通性尚未完全确定。地壳深部和上地幔的高分辨率图像，一直到板片，将有助于详细揭示大规模岩浆系统，并将揭示俯冲板片的复杂细节，地幔楔的蛇纹石化的可能性，以及地幔弧前莫霍面的弱反射率。本项目中采用的波形处理和反演技术最初是由地震科学有限责任公司开发的，用于绘制低渗透油气层水力刺激期间产生的裂缝。在该项目下，科罗拉多矿业学院和美国地质调查局（USGS）将合作使用该技术对圣海伦斯火山岩浆系统进行高分辨率成像。该奖项反映了NSF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。

Mount St. Helens, in the Cascadia Subduction Zone, is an active volcano and is most well known for the devastating 1980 eruption which is widely regarded as the most disastrous volcanic eruption in the United States history in terms of loss of human life and damage to infrastructure. In fact, the United States Geological Survey (USGS) regards Mount St. Helens as a very high threat volcano. The work planned here will illuminate the Mount St. Helens magmatic plumbing system and help scientists better forecast impending volcanism and its possible duration. Such knowledge will be extremely useful for volcanic hazard mitigation and help save human lives. This project is a collaboration between a university (Colorado School of Mines) and a government institution (USGS) to extend the application of a cutting-edge technology, originally developed by a private enterprise (Seismic Science LLC) to image hydraulic fractures in oil & gas reservoirs, for monitoring volcanic systems for the betterment of the society. The investigators believe this collaboration will foster further cooperation, technology transfer, and exchange of ideas between the hydrocarbon industry and government entities. The processes and techniques developed under this project could potentially be extended to the other subduction zones in order to help image megathrust and volcanic systems all over the world.The architecture of the Mount St. Helens magmatic system and the spatio-temporal changes resulting from magma production, transport, and storage are poorly understood. To address these questions, extensive seismic data, in the form of active-seismic surveys and passive recordings, have been acquired over the past three decades and also as part of the EarthScope program. The investigators will use local earthquake recordings from both the active-seismic data (comprising of two nodal geophone arrays and PASSCAL Texan geophones) and broadband seismometers and the active-seismic waveform data to generate a high-resolution time-lapse 3-dimensional image of the Mount St. Helens magmatic system using waveform inversion. These images will extend from the shallow upper-crust all the way to the subducting slab underneath Mount St. Helens, thereby helping to shed light on the complete architecture of the magmatic system, the connections between different magma bodies, and the physical state of the rocks. Knowledge of the magmatic system at Mount St. Helens (in terms of its architecture and spatio-temporal changes) will provide valuable insight into a number of key scientific challenges including questions about crustal evolution, magma generation in the mantle, magma transport from the upper mantle to the shallow crust, the structure of magma reservoirs, and forecasting volcanism. The high-resolution spatio- temporal 3-dimensional images will be especially useful in understanding stress changes associated with magma emplacement/inflation and in deciphering the transport of melts in the crust and upper mantle. Also, the scale, extent, and connectivity of magma in the crust and mantle beneath Mount St. Helens is not fully established. High-resolution images of the deep crust and upper mantle, all the way to the slab, will help unravel the large-scale magmatic system in detail and will reveal intricate details of the subducting slab, the possibility of serpentinization of the mantle wedge, and the weak reflectivity of the Moho in the mantle fore- arc. The waveform processing and inversion technology employed in this project was originally developed at Seismic Science LLC for mapping fractures generated during hydraulic stimulation of low-permeability oil and gas formations. Under this project, Colorado School of Mines and United States Geological Survey (USGS) will collaborate to employ this technology to image the Mount St. Helens magmatic system at high resolution.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.