Seismic Investigation of Mauna Loa Volcano, Hawaii

夏威夷岛上的莫纳罗亚火山是世界上最大的火山。与其东南部的邻居基拉韦厄相比，毛纳罗亚由于其陡峭的坡度、高的海拔和相对缺乏活动而没有得到广泛的调查。2022年11月27日，莫纳罗亚山顶火山口开始喷发，并延伸到东北裂谷地带，这是火山东北侧翼的一条裂缝。莫纳罗亚火山过去曾在东北和西南裂谷地带发生过喷发，而后者周围的人口已经增长。因此，在下一次喷发发生之前，研究人员必须了解岩浆“管道系统”。在这个项目中，Pi团队将在火山及其周围部署54个地震仪，为期三个月，以获取本地和远程地震的震动记录。他们将分析来自这些地震仪和其他地震仪的数据，以绘制当地地震地图，并使用所有记录的地震数据制作地下详细的3D图像(类似于医院的CT扫描)。新的图像和当地地震的模式将显示岩浆室和岩浆上升到地表的可能途径，与未来研究结果的比较将显示岩浆是如何随着时间的推移在火山下方迁移的。新的发现将帮助PI团队、他们在美国地质勘探局夏威夷火山天文台的合作者，以及其他科学家更好地了解与莫纳罗亚有关的地震和火山灾害。该项目还将为一名博士后学者和两名本科生提供火山地震学方面的培训。在这个为期三年的项目中，该团队将把最先进的地震技术应用于美国地质调查局夏威夷火山观测站的永久地震台和节点阵列在为期三个月的实验中记录的数字数据，以评估莫纳罗亚火山的高分辨率速度结构和地震特征。这些数据将被用来生成自动地震目录，为岩浆系统成像，估计震源区附近的现场泊松比，并检查地震速度的时间变化。新开发的速度模型在解决管道和岩浆室以及改善绝对地震位置方面具有非常重要的价值。高分辨率的现场泊松比对追踪岩浆运动和估算部分熔体的比例有很大帮助。本项目将解决以下问题：1.高分辨率Vp、Vs和Vp/Vs模型的同时反演将揭示有关岩浆系统和可能的岩浆体的什么信息？(这些岩浆体在2022年的喷发中扮演了什么角色？为什么2022年的喷发在休眠38年后产生了如此小的喷发量？)2.三维速度模型的绝对地震位置约束将告诉我们有关毛纳罗亚断裂带的什么？3.根据波形互相关数据估计的高分辨率原位Vp/VS比将揭示近震源区的时空特征？4.与夏威夷其他地区和其他火山相比，毛纳罗亚的长期地震速度变化如何？这一奖项反映了这是NSF的法定使命，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。

Mauna Loa volcano on the Island of Hawaii is the world’s largest volcano. Compared with its southeastern neighbor Kilauea, Mauna Loa has not been extensively investigated due to its steep slopes, high elevation, and relative lack of activity. On November 27, 2022, an eruption began in the summit crater of Mauna Loa and extended to the Northeast Rift Zone, a crack on the northeast flank of the volcano. Past eruptions at Mauna Loa have occurred on both the Northeast and Southwest Rift Zones, and the population has grown around the latter. It is therefore imperative for researchers to understand the magmatic “plumbing system” before the next eruption takes place. In this project, the PI team will deploy 54 seismometers on and around the volcano for three months to obtain records of shaking from local and distant earthquakes. They will analyze data from these and other seismometers to map local earthquakes, and make a detailed 3D image of the subsurface (similar to a CT scan at a hospital) using data from all of the recorded quakes. The new images and the pattern of local earthquakes will show magma chambers and possible routes for magma to ascend to the surface, and comparisons with results from future studies will show how magma is migrating below the volcano over time. The new findings will help the PI team, their collaborators at the USGS Hawaiian Volcano Observatory, and other scientists better understand seismic and volcanic hazards associated with Mauna Loa. This project will also provide training in volcano seismology for a postdoctoral scholar and two undergraduate students.In this three-year project, the team will apply the state-of-the-art seismic techniques to the digital data recorded by the permanent seismic stations at the USGS Hawaiian Volcano Observatory and a nodal array during a three-month experiment to assess the high-resolution velocity structure and seismic characteristics of Mauna Loa volcano. The data will be used to generate an automatic earthquake catalog, to image the magmatic system, to estimate in-situ Poisson’s ratio in the near earthquake source regions, and to examine temporal variations in seismic velocity. The newly developed velocity models are invaluable in resolving conduits and magma chambers and improving absolute earthquake locations. In situ Poisson’s ratios with high-resolution are of great help to tracking magma movement and estimating the fraction of partial melt. The following questions will be addressed in this project: 1. What will the simultaneous inversions of the high-resolution Vp, Vs, and Vp/Vs models reveal about the magmatic system and possible magma bodies? (What role did these magma bodies play in the 2022 eruption and why did the 2022 eruption produce such a small eruptive volume after over 38 years of repose?) 2. What will the absolute earthquake location constraints from 3D velocity models tell us about the fault zones in Mauna Loa? 3. What will the high-resolution in situ Vp/Vs ratios estimated from waveform cross-correlation data reveal about the spatial and temporal characteristics in the near-source region? 4. How do the long-lasting seismic velocity variations in Mauna Loa compare to those in other parts of Hawaii and at other volcanoes?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.