Collaborative Research: Waves in Volcanic Conduit-crack Systems and Very Long Period Seismicity at Kilauea Volcano, Hawaii

合作研究：夏威夷基拉韦厄火山的火山管道裂缝系统中的波浪和甚长周期地震活动

• 批准号: 1624557
• 负责人: Leif Karlstrom
• 金额: $ 22.1万
• 依托单位: University of Oregon Eugene
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-10-01 至 2020-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1624557&HistoricalAwards=false
• 关键词: Collaborative; Research; Waves; Volcanic; Conduit; Collaborative; Research; Waves; Volcanic; Conduit

An overarching goal of volcanology is to characterize eruptive activity and link this to the physical processes governing magma ascent and eruption, which are generally hidden from direct observation. This proposal will develop a modeling framework to image the inner workings of active volcanoes, such as at Kilauea, Hawaii, USA. Kilauea represents a unique natural laboratory: it exhibits frequent eruptions, a dense instrumental monitoring network to record these eruptions, and a long history of scientific study. Recent activity at the Halemaumau vent, from 2008 to the present day, is the primary observational target. Rock falls from the crater walls onto the active lava lake generate oscillations of the magma and gas within the conduit, explosions, and lake height variations, as evidenced through oscillatory ground motion recorded on the local sensor network. Models for this behavior must explicitly consider bubble growth, complex conduit geometry that includes branching cracks, and stratified, multiphase fluid flow to achieve consistency between seismic data, video of lake level fluctuations, chemical data that constrain gas contents, and textural data that constrain near-surface magma density and bubble content. Theoretical understandings of magma flow, gas solubility laws, and bubble growth gained as a result of this study should benefit the study of active volcanoes generally, as well as diverse applications arising in Earth science and industry that involve flow of bubbly fluids through networks of cracks. Both the modeling tools and results could ultimately be used to monitor active volcanoes, understand their dynamics, and inform eruption forecasts.This proposal describes a framework for the study of volcanic activity and interpretation of seismic observations at active, open vent volcanoes. The primary application is to short term (tens of minutes) unrest episodes at Kilauea volcano, Hawaii, associated with rock falls from the crater walls onto the active lava lake surface, which induce oscillations of the magma and gas within the conduit, explosions, and lake height variations, as evidenced through oscillatory ground motion recorded on nearby seismometers and tilt meters. These natural experiments provide a unique test for unsteady conduit flow models, which depend critically on knowing conduit geometry and fluid properties of magma (rheology, multiphase character, volatile content, solubility law), all of which are generally hidden from direct observation. The project team will develop a numerical modeling framework for multiphase flow, at much shorter timescales than typically studied, with seismic wave propagation through bubbly magma in conduits that include branching dikes and sills at depth, as is expected at many volcanoes. Pressure changes in the conduit-crack system cause elastic deformations of the conduit and crack walls. Coupling to the solid Earth enables prediction of seismic signals associated with waves and resonant oscillations of the magmatic system. Buoyancy, compressibility, viscous drag, and non-equilibrium bubble growth and resorption ? all of which vary with depth ? must be accounted for to predict mode properties. Branching dikes/sills at depth partially control mode periods and ground displacement. Observable periods and decay rates of seismic signals are thus linked directly to the evolving depth distribution of gas, conduit architecture, and viscous drag. Inversion of these signals will provide new constraints on the shallow magmatic system and total volatile content at Kilauea, and a new framework for probing unsteady eruptive processes.

火山学的总体目标是表征爆发活动，并将其与控制岩浆上升和喷发的物理过程联系起来，这些过程通常隐藏在直接观察中。该提案将开发一个建模框架，以图像活跃火山的内部运作，例如在美国夏威夷的Kilauea。 Kilauea代表着一个独特的天然实验室：它表现出频繁的喷发，密集的工具监测网络以记录这些喷发，以及悠久的科学研究历史。从2008年到今天的Halemaumau通风口的最新活动是主要的观察目标。岩石从火山口壁上落到活跃的熔岩湖上产生导管内岩浆和气体的振荡，爆炸和湖泊高度变化，这是通过在当地传感器网络上记录的振荡地面运动证明的。这种行为的模型必须明确考虑气泡的生长，包括分支裂纹的复杂导管几何形状以及分层的多相流体流，以实现地震数据之间的一致性，湖泊水平波动的视频，限制气体内容的化学数据以及限制近乎表面岩浆密度和气泡含量的质地数据。对岩浆流量，气体溶解度定律和气泡生长的理论理解，应受益于对活跃火山的研究，以及在地球科学和工业中产生的多种应用，涉及通过裂缝网络流动的流体流动。建模工具和结果最终都可以用来监测活跃的火山，了解其动态并为喷发预测提供信息。该提案描述了一个研究火山活动的框架，并解释了活跃的开放通风口火山的地震观测。主要的应用是在夏威夷基拉韦阿火山的短期（数十分钟）的动荡发作，与岩石从火山口掉落到活跃的熔岩湖表面相关，该岩石湖表面诱导了岩浆和气体在导管，爆炸，爆炸和湖泊身高变化中的振荡，这是通过振荡的地面运动在附近的sesemors和tigry semorsemers和Timsorsers的振动。这些自然实验为不稳定的导管流模型提供了独特的测试，该测试批评岩浆的导管几何形状和流体特性（流变学，多相特征，挥发性含量，溶解度定律），所有这些通常都隐藏在直接观察中。项目团队将在比通常研究的时间范围内开发一个用于多相流的数值建模框架，并且在许多火山上预期的是，在包括深度的分支堤防和窗台的情况下，通过气泡岩浆进行地震波传播。导管裂缝系统的压力变化会导致导管和裂纹壁的弹性变形。与固体地球的耦合可以预测与波浪和岩浆系统共振振荡相关的地震信号。浮力，可压缩性，粘性阻力和非平衡气泡生长和吸收？所有这些都随着深度而变化吗？必须考虑以预测模式属性。在深度部分控制模式周期和地面位移的深度分支堤防/窗台。因此，可观察到的地震信号的时期和衰减率直接与气体​​，导管架构和粘性阻力的深度分布直接相关。这些信号的反转将对Kilauea的浅层岩浆系统和总挥发性含量提供新的约束，并为探测不稳定的喷发过程的新框架提供了新的限制。