Collaborative Research: Magnetotelluric and Seismic Investigations of the Distribution of Magmatic and Hydrous Fluids Beneath Yellowstone

合作研究：黄石地下岩浆和含水流体分布的大地电磁和地震调查非技术描述位于爱达荷州、蒙大拿州和怀俄明州的黄石火山系统在过去的210万年里产生了三次大规模的火山爆发，最近的一次是在64万年前。直到7万年前，较小的火山爆发一直持续到今天，黄石的火山系统拥有一个动态的热液系统，每年发生数千次小型地震。在这个项目中，来自威斯康星大学麦迪逊分校和俄勒冈州立大学的一个团队正在部署一个敏感的大地电磁（MT）设备网络，该设备记录了黄石国家公园内外地球地磁场和地电场的自然变化。该团队正在使用MT数据来感知地壳和地幔电导率的微小变化，并且通过将MT和黄石地下结构的地震测量相结合，该团队将推断岩浆系统中流体的分布；黄石公园的岩浆是如何储存的；以及它在该地区的流动性。这对黄石公园未来的火山活动以及此类活动可能造成的潜在危害具有启示意义。该项目还促进了首席研究员Ninfa Bennington的职业生涯，她是一位早期的职业女性科学家，并涉及来自传统上代表性不足群体的研究生和本科生的实地工作。该团队正在制作外展材料，每年将通过威斯康星大学麦迪逊分校地质博物馆的互动亭与4万多人分享，并正在开发一款智能手机应用程序，与更广泛的受众分享这些内容。此外，他们正在与黄石国家公园合作，为国家公园网站创建详细介绍实地工作和项目结果的内容。这些努力将确保这个项目的成果惠及广泛的受众。项目技术描述以前对黄石（YS）地壳和上地幔的地震和大地电磁（MT）研究已经提供了岩浆流体进入YS地壳火山系统的起源和迁移的见解。然而，关于阳山岩浆活动的产生以及这些岩浆流体在地壳火山系统内的迁移和储存，仍然存在重要的问题。研究小组提出了三个相互竞争的火山活动假说，其中包括不同的解释：1)岩浆流体在上地幔/下地壳深处的起源和位置；2)这些岩浆流体进入中上部地壳的首选迁移路径；3)岩浆储层的最终分布；4)岩浆储层的组成；5)对未来YS火山活动的影响。为了评估这些活火山活动的假设，研究小组正在东太平洋地区进行高分辨率的MT调查，并将这些观察结果与现有数据结合起来，反演东太平洋地壳和上地幔的三维电阻率结构。该团队还利用多尺度技术分别反演地震数据，以确定同一地区的地震速度结构。所得到的模型对地下的不同性质很敏感（例如，MT对熔体的存在和地震速度对温度升高的影响），因此提供了独立的结构约束。该团队将通过联合解释，将这些独立的、空间上一致的模型结合起来，检验他们关于黄石岩浆系统中岩浆和相关流体的分布和行为的假设。

Collaborative Research: Magnetotelluric and Seismic Investigations of the Distribution of Magmatic and Hydrous Fluids Beneath YellowstoneNon-technical descriptionThe Yellowstone volcanic system in Idaho, Montana, and Wyoming has produced three massive volcanic eruptions in the past 2.1 million years, the most recent 640,000 years ago. Smaller eruptions followed until 70,000 years ago, and today, Yellowstone's volcanic system hosts a dynamic hydrothermal system with thousands of small magnitude earthquakes occurring annually. In this project, a team from the University of Wisconsin-Madison and Oregon State University is deploying a network of sensitive magnetotelluric (MT) equipment, which record natural variations in Earth's geomagnetic and geoelectric fields, in and around Yellowstone National Park. The team is using MT data to sense small changes in conductivity of the crust and mantle and, by combining MT and seismic measurements of the structure beneath Yellowstone, the team will infer the distribution of fluids in the magmatic system; how magma is stored at Yellowstone; and how mobile it is within the region. This has implications for future volcanic activity at Yellowstone and potential hazards such activity might pose.This project is also fostering the career of principal investigator Ninfa Bennington, an early career female scientist, and involves field work by both graduate and undergraduate students from traditionally underrepresented groups. The team is creating outreach materials that will be shared with more than 40,000 people per year via interactive kiosks at the Geology Museum of the University of Wisconsin-Madison, and is developing a smartphone app to share this content with an even broader audience. In addition, they are working with Yellowstone National Park to create content detailing the field work carried out, and the results of the project, for the National Park Web site. These efforts will ensure the results from this project reach a wide audience.Technical Description of ProjectPrevious seismic and magnetotelluric (MT) studies of the crust and upper mantle beneath Yellowstone (YS) have provided insight into the origin and migration of magmatic fluids into the YS crustal volcanic system. However, important questions remain concerning the generation of magmatism at YS and the migration and storage of these magmatic fluids within the crustal volcanic system. The research team has developed three competing hypotheses describing active volcanism at YS, which include different explanations for: 1) the origin and location of magmatic fluids at upper mantle/lower crustal depths 2) the preferred path of migration for these magmatic fluids into the mid- to upper-crust, 3) the resulting distribution of the magma reservoir, 4) the composition of the magma reservoir, and 5) implications for future volcanism at YS. To evaluate these hypotheses for active volcanism at YS, the team is conducting a high-resolution MT survey in the YS region, and is combining those observations with existing data to invert for the 3D resistivity structure in the crust and upper mantle underneath YS. The team is also separately inverting seismic data to determine the seismic velocity structure in the same region using multi-scale techniques. The resulting models are sensitive to different properties of the subsurface (e.g., MT to presence of melt and seismic velocity to increased temperature), and therefore provide independent structural constraints. The team will combine these independent, spatially coincident models through joint interpretations test their hypotheses about the distribution and behavior of magmatic and related fluids in the Yellowstone magmatic system.