Systematic mapping of magma bodies under Cascades volcanoes

火山喷发威胁公共安全，并可能造成严重的社会和经济损失。大陆弧形火山的大部分喷发是由熔岩或岩浆提供的，这些熔岩或岩浆聚集在地壳某处的储集层中。然而，在大多数活动系统下，地壳岩浆系统的大小、分布和深度及其在火山之间的变异性仍然知之甚少。该项目的目的是通过提供沿一条弧线、华盛顿、俄勒冈州和加利福尼亚州北部的喀斯喀兹弧线的岩浆系统的天气学、整体地震成像调查，来量化这种可变性。这条弧线对美国的人口中心构成了最大的威胁。这项研究利用了大量新部署或升级的地震仪，这些地震仪安装在美国地质调查局运营的许多高威胁喀斯喀兹火山的山顶几公里内。这些仪器首次提供可以通过岩浆储集层的规模的地震信号。这些信号将允许对大多数主要喀斯喀特火山下面的岩浆系统进行首次统一采样。该项目支持康奈尔大学的一名博士后和一名研究生，他们将与美国地质调查局喀斯喀兹火山天文台(CVO)的科学家合作。该项目将帮助CVO建立一个持续监测火山活动的工作流程。该项目将利用CVO升级后的地震监测网络，并应用几种强大的地震技术来系统地对喀斯喀兹火山弧沿线的关键火山中心进行成像。接收器功能经常显示火山附近的大幅度信号，这在其他地方是看不到的。它们将用于所有接近顶峰的站点，并用于识别和描述尖锐的界面，特别是产生独特地震速度反转的岩浆体顶部。环境噪声成像将在接收函数采样的区域内测量S波的绝对速度，以约束关键的物理特性。这些测量和其他测量还得到了一套全面的全波形正演模型的补充，以更好地了解有限波长信号与岩浆体的相互作用。这些测量将在可变几何形状的熔波速度关系的背景下被联合反转和解释。环境噪声分析还将作为寻找火山附近地震波速的时间变化的基线，这是岩浆运动的潜在指示。这项工作首次提供了多个火山的岩浆管道系统的稳健、一致的图像，并将提供更系统的岩浆储集层特征评估。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。

Volcanic eruptions threaten public safety and can cause severe social and economic damage. Most eruptions of continental arc volcanoes are supplied from molten rock, or magma, that builds up in a reservoir somewhere in the crust. However, the size, distribution and depth of crustal magma systems, and their variability between volcanoes, remain poorly known beneath most active systems. The aim of the project is to quantify this variability by providing a synoptic, holistic seismic imaging survey of magma systems along one arc, the Cascades arc of Washington, Oregon and northern California. This arc poses the largest threat to population centers of any in the United States. The study leverages abundant newly deployed or upgraded seismographs placed within a few kilometers of the summits of many of the high-threat Cascades volcanoes, operated by the U.S. Geological Survey. These instruments for the first time provide seismic signals at a scale that could pass through the magma reservoirs. The signals will allow for the first uniform sampling of the magma systems beneath most major Cascades volcanoes. The project supports a postdoc and a graduate student at Cornell University, who will collaborate with scientists at the U.S. Geological Survey’s Cascades Volcano Observatory (CVO). The project will help CVO set up a workflow for continuously monitoring volcanic activities. The project will take advantage of the upgraded seismic monitoring network of CVO and apply several robust seismic techniques to image key volcanic centers along the Cascades volcano arc systematically. Receiver functions frequently show large-amplitude signals near volcanoes that are not seen elsewhere. They will be derived for all near-summit stations, and used to identify and describe sharp interfaces, particularly the tops of magma bodies that produce distinctive seismic velocity inversions. Ambient-noise imaging will be conducted to measure absolute S-wave velocities in the regions sampled by receiver functions, to constrain critical physical properties. These and other measurements are complemented by a comprehensive suite of full-waveform forward models to understand better how finite-wavelength signals interact with magma bodies. These measurements will be jointly inverted and interpreted in a context of variable geometry melt-wavespeed relationships. The ambient noise analyses will also serve as a baseline in a search for temporal changes in seismic wavespeeds near volcanoes, a potential indication of magma movements. The work, for the first time, provides robust, consistent images of magma plumbing systems at multiple volcanoes and will provide more systematic assessments of magma reservoir characteristics.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.