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火山相比，莫纳罗亚火山由于其陡峭的山坡、高海拔和相对缺乏活动而没有得到广泛的研究。2022年11月27日，冒纳罗亚火山的山顶火山口开始喷发，并延伸到东北裂谷带，这是火山东北侧面的一条裂缝。莫纳罗亚火山过去的喷发发生在东北裂谷区和西南裂谷区，而后者周围的人口也在增长。因此，在下一次喷发发生之前，研究人员必须了解岩浆的“管道系统”。在这个项目中，PI团队将在火山上和周围部署54个地震仪，为期三个月，以获取当地和远处地震的震动记录。他们将分析这些地震仪和其他地震仪的数据，绘制当地地震图，并利用所有记录的地震数据绘制详细的地下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房和岩浆上升到地表的可能路线，并与未来研究的结果进行比较，将显示岩浆如何随着时间的推移在火山下方迁移。新的发现将帮助PI团队，他们在美国地质调查局夏威夷火山观测站的合作者，以及其他科学家更好地了解与莫纳罗亚火山有关的地震和火山危险。该项目还将为一名博士后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，研究小组将运用最先进的地震技术，对美国地质调查局夏威夷火山观测站的永久地震站和节点阵列记录的数字数据进行为期三个月的实验，以评估莫纳罗亚火山的高分辨率速度结构和地震特征。这些数据将用于生成自动地震目录，成像岩浆系统，估计地震震源附近地区的泊松比，并检查地震速度的时间变化。新建立的速度模型在确定管道和岩浆房以及确定地震的绝对位置方面具有不可估量的价值。高分辨率的原位泊松比对跟踪岩浆运动和估计部分熔体的比例有很大的帮助。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岩浆系统和可能的岩浆体的哪些信息？（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38年的沉寂之后产生了如此小的喷发量？）2. 从三维速度模型得到的绝对地震位置限制会告诉我们莫纳罗亚断裂带的什么信息？3. 从波形互相关数据估计的高分辨率原位Vp/Vs比值将揭示近源区域的时空特征？4. 莫纳罗亚火山的长期地震速度变化与夏威夷其他地区和其他火山的地震速度变化相比如何？该奖项反映了美国国家科学基金会的法定使命，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。

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.