Insights into Episodic Caldera Collapse and Magmatic Systems from the 2018 Eruption of Kilauea Volcano

当大量岩浆快速喷发时，火山破火山口就会崩塌，导致覆盖在地壳上的岩浆塌陷到地下岩浆库中。火山口塌陷发生在爆炸性喷发和熔岩流形成的喷发期间；幸运的是，这两种情况都相对罕见。2018年夏威夷火山喷发摧毁了700所房屋，造成8亿美元的损失。相关的火山口崩塌是迄今为止历史上监测最好的一次。在2.5个月的时间里，夏威夷火山国家公园内这个有着数百年历史的火山口的底部下降了500米，体积增加了0.8平方公里。了解崩塌过程是至关重要的，因为上覆地壳的重量支撑着这些喷发。虽然了解了火山口崩塌的基本原理，但2018年收集的前所未有的数据将使我们能够解决一级问题，包括：崩塌所需的地壳应力和岩浆压力条件是什么？包围崩塌的环形断层系统的地下几何形状是什么？为什么坍缩发生在离散的事件中，哪些物理性质控制了这些事件的特征？火山口下岩浆储存系统的本质是什么？它们是如何与喷口相连的？对这些独特数据的建模将使我们对火山口崩塌的理解有一个定量的飞跃。该项目将帮助一名研究生了解美国的火山灾害。2018年发生了62次离散事件，火山口从几米下降到近10米，并伴有5.2至5.4级地震。崩塌伴随着显著的膨胀变形抵消，随后是减速的通货紧缩，类似于其他玄武岩火山口崩塌的行为。关于破火山口环形断层是向内倾斜还是向外倾斜，一直存在相当大的争论。该项目将使用有限元（FEM）建模结合高速率GPS数据的反演来约束环断层倾角和下伏岩浆的可压缩性，从而约束泡状性。该研究将进一步利用崩塌前，特别是崩塌后的GPS和InSAR数据来约束神秘的峰顶岩浆系统的几何形状、大小和连通性。崩塌的动力学是用一个模型来分析的，在这个模型中，火山口块体的重量是由底部的岩浆压力和两侧与速率和状态相关的摩擦来平衡的。岩浆的流动是由岩浆房和喷发点之间的压力差驱动的。反复崩溃事件的模型预测与事件之间的时间，它们的持续时间，位移和岩浆室压力的增加进行比较。该模型阐明了火山口崩塌的条件，以及崩塌如何维持原本会停止的火山喷发。测量到的喷发流量波动将用于进一步限制岩浆系统内的压力。我们对共塌变形的分析自然导致了VLP地震的模型。将计算合成波形，并与低通滤波后的地震观测结果进行比较。累积VT地震活动性与崩塌间沉降的显著相关性强烈表明，崩塌前环断层上的断层蠕变，为断层发育和腔室压力历史提供了见解。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。

Volcanic caldera collapse occurs when large volumes of magma erupt rapidly, causing the overlying the crust to founder into the subterranean magma chamber. Caldera collapse occurs during both explosive and lava flow forming eruptions; both are fortunately relatively rare. The 2018 eruption of Kīlauea volcano in Hawai‘i destroyed 700 homes and led to $800 million in damage. The associated caldera collapse was by far the best monitored in history. In 2.5 months, the floor of the centuries-old caldera, within Hawai‘i Volcanoes National Park, dropped up to 500 meters and increased in volume by 0.8 km3. It is crucial to understand the collapse process because the weight of the overlying crust acts to sustain these eruptions. While the basics of caldera collapse are understood, the unprecedented data collected in 2018 will allow us to address first order questions, including: What are the crustal stress and magma pressure conditions necessary for collapse? What is the sub-surface geometry of the ring fault system bounding the collapse? Why did collapse occur in discrete events, and what physical properties controlled the character of these events? What is the nature of sub-caldera magma storage systems and how do they connect to the eruptive vents? Modeling of these unique data will lead to a quantitative leap in our understanding of caldera collapse. The project will support a graduate student to understand volcanic hazards in the U.S.The 2018 collapse of occurred in 62 discrete events in which the caldera dropped from several to nearly 10 meters, accompanied by magnitude 5.2 to 5.4 earthquakes. Collapses were accompanied by remarkable, inflationary deformation offsets followed by decelerating deflations, similar to behavior at other basaltic caldera collapses. There has been considerable debate as to whether caldera ring-faults are inward or outward dipping. This project will use finite element (FEM) modeling combined with inversion of high-rate GPS data to constrain the ring-fault dip and the compressibility, and hence vesicularity, of the underlying magma. The research will further use pre- co-, and in particular post-collapse GPS and InSAR data to constrain the geometry, size and connectivity of the enigmatic summit magma system. The dynamics of collapse are analyzed with a model in which the weight of the caldera block is balanced by magma pressure at its base and rate-and-state dependent friction on its sides. Flow of magma is driven by the pressure difference between the magma chamber and the eruption site. Model predictions of repeated collapse events are compared to the time between events, their duration, displacement, and magma chamber pressure increase. The model elucidates the conditions for caldera collapse, and how collapse sustains eruptions that would otherwise cease. The measured surges in eruptive flux will be used to further constrain pressures within the magma system. Our analysis of co-collapse deformation leads naturally to a model for the VLP earthquakes. Synthetic waveforms will be computed that can be compared to low-pass filtered seismic observations. A striking correlation of cumulative VT seismicity with inter-collapse subsidence strongly suggests fault creep on the ring-fault prior to collapse, providing insights into fault development and chamber pressure history.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.