An Integrated Analysis of Seismicity, Infrasound, and High-Resolution SO2 Measurements to Determine the Source of Low-Frequency Seismicity at Villarrica Volcano, Chile

火山产生丰富多样的地震信号，这与典型地震产生的信号不同。虽然对地震前兆信号的识别大大提高了预测火山爆发的能力，但对火山信号产生的具体机制的了解还只是大致了解。例如，低频地震震颤与流体运动有关，但许多模型可以解释任何一座火山的地震震颤。通过整合高分辨率的地震、声波和气体发射数据，本研究将确定Villarrica火山气体通量与地震震颤特征之间的关系。自1984年以来，维拉里卡一直有持续的气体排放和一个持续的、温和的、爆炸性活动的活跃熔岩湖。由于持续的低水平活动，可以安全地从山顶火山口直接测量气体排放、地震活动和低频声音（次声）。这项研究将同时测量地震活动性、次声和气体排放。研究人员将部署宽带站阵列，以定位和跟踪低频地震和火山构造地震活动的深度，并使用分布式次声麦克风来描述爆炸性放气活动。在为期2-3周的现场活动中，他们还将收集高时间分辨率的二氧化硫排放数据，以及放气活动的热视频和视觉视频。所有这些数据将被联合解释，以表征和量化不同的放气方式。一个为期15个月的地震仪和麦克风的部署将确保大部分的放气方式得到很好的采样。他们在较短的野外活动中开发的放气方式分类方案将使他们能够在整个部署期间计算气体排放的代理数据集，以便他们可以解决有关长期活动周期的问题，以及火山系统上较深的当地火山地震和较远的地震之间的关系。这个项目的变革潜力在于对这些数据的整合。地震分析将以现有技术的坚实基础为基础。次声分析现在被认为是监测通风口系统的关键，但次声数据的某些方面还没有得到很好的理解。在美国国家科学基金会（National Science Foundation）的支持下，最近研制出一种新型紫外相机，可以对二氧化硫排放的速度进行成像，其速度与火山喷发过程相当。通过建立数据之间的经验联系，本研究将测试气体排放产生地震活动和声音的理论模型，并产生关于喷发过程的重要新知识。

Volcanoes produce a rich variety of seismic signals that are unlike those generated during typical earthquakes. While great improvements in the ability to forecast volcanic eruptions have come from recognizing precursory seismic signals, knowledge of the specific mechanisms responsible for the volcanic signals is only generally understood. For example, low-frequency seismic tremor is linked to fluid movement, but many models can explain seismic tremor at any one volcano. By integrating high-resolution seismic, acoustic, and gas emission data, this study will determine the relationship between gas flux and the characteristics of seismic tremor at Villarrica volcano. Villarrica has had persistent gas emission and an active lava lake with continuous, mild, explosive activity since 1984. Because of the continuous low-level activity, direct measurements of emissions of gas, seismicity, and low-frequency sound (infrasound) can safely be made from the summit crater. This study will use simultaneous measurements of seismicity, infrasound and gas emissions. The researchers will deploy arrays of broadband stations to locate and track the depth of low-frequency and volcano-tectonic seismicity, along with distributed infrasonic microphones to characterize the explosive outgassing activity. During 2-3 week field campaigns, they will also collect high-time resolution SO2 emission data, and thermal and visual video of the outgassing activity. All these data will be interpreted jointly to characterize and quantify different styles of outgassing. A 15-month deployment of seismometers and microphones will assure that a significant portion of the outgassing styles is well sampled. The classification scheme for outgassing style they develop during the shorter field campaigns will allow them to calculate a proxy data set for gas emission during the full duration of the deployment so that they may address questions about long-term cycles of activity and the relationship between both deeper local volcanic earthquakes and distant earthquakes on the volcanic system.The transformative potential of this project lies in the integration of these data. The seismic analysis will be based on the strong foundation of established techniques. Infrasound analysis is now seen as critical for monitoring open-vent systems, yet some aspects of infrasound data are not well understood. A novel UV camera, recently developed with support from the National Science Foundation, can image SO2 emission at a rate comparable to eruptive processes. By establishing empirical links between the data, this study will test theoretical models for the generation of seismicity and sound from gas emission and generate important new knowledge on eruptive processes.