Collaborative Research: Quantifying Explosive Volcanism in Alaska Using Seismo-acoustic Wavefields Recorded by USArray

合作研究：使用 USArray 记录的地震声波场量化阿拉斯加的爆发性火山活动阿拉斯加拥有 130 座潜在的活火山，其中 50 多座在历史时期一直处于活动状态。平均每年有 2 座火山处于喷发状态。阿留申群岛、阿拉斯加半岛和库克湾的火山能够突然爆发，形成火山灰云，这对这条交通繁忙的空中走廊上的客机和货机有潜在的危险。阿拉斯加的许多火山都位于偏远地区，环境恶劣。监测这些火山是一项艰巨的挑战，而且许多火山没有配备仪器。次声（频率低于人耳听觉阈值 20 Hz 的声波）是一种快速发展的技术，用于了解和监测火山喷发。中等规模的爆炸性喷发会产生强大的次声信号，这些信号可以在大气中有效传播数千公里。然而，迄今为止，这些信号是由稀疏的次声传感器网络记录的，限制了我们对其源产生和通过大气传播的理解。 EarthScope 可移动阵列 (TA) 目前正在阿拉斯加部署，为世界上最活跃的火山地区之一带来有史以来最密集的地震和次声波组合网络。利用这一新颖的数据集，该项目将提高火山喷发声学预警系统的能力，以确保航空安全，并将评估大型传感器网络（如 TA）对火山监测的潜在贡献。在项目结束时，由这项工作产生的可操作火山声学监测系统将在阿拉斯加火山观测站实施。这项工作将利用前所未有的地震声学数据集，随着技术援助通过密集空间波场采样记录阿拉斯加的常规爆发性火山活动，该数据集开始变得可用。火山地震声学是一个快速发展的研究领域，其基本问题仍然存在于火山喷发的震源机制、震源方向性、大气传播和地震声耦合等方面。该项目将侧重于使用新方法检测、区分和定位信号；量化地震声波场；调查来源机制；量化地震声波耦合；并了解次声在时空变化的大气中的传播。通过数据分析和建模相结合，我们将表征和量化在距爆炸喷发源一定距离和方向记录的各种地震和次声信号。我们将解决以下问题：（1）观测到的火山喷发声波和地震信号如何随震源距离和方位角变化？ (2) 不同类型的爆炸性喷发的声波传播有何不同？ （3）从远距离地震声学资料中可以确定哪些火山震源信息？ (4) 以往火山次声波场采样的局限性是什么？ (5) 阿拉斯加还有哪些其他次声源？我们的团队将与阿拉斯加大学费尔班克斯分校的 EarthScope 国家办公室合作，帮助突出这项研究及其影响。展示阿拉斯加火山喷发的地震声波场的多媒体产品将通过网络分发，用于公共信息包以及教育和宣传。事件目录和相关数据产品将公开，其中著名的次声事件将上传到 IRIS TA 次声参考事件数据库 (TAIRED)。

Collaborative Research: Quantifying explosive volcanism in Alaska using seismo-acoustic wavefields recorded by USArrayAlaska is home to 130 potentially active volcanoes, of which more than 50 have been active in historical times. On average 2 volcanoes are in a state of eruption every year. Volcanoes in the Aleutian Islands, Alaska Peninsula, and Cook Inlet are capable of sudden, explosive, ash-cloud forming eruptions, which are potentially hazardous to passenger and freight aircraft along this heavily travelled air corridor. Many of Alaska?s volcanoes are in remote locations with harsh environments. Monitoring these volcanoes represents a formidable challenge and many of the volcanoes are not instrumented. Infrasound (acoustic waves with frequencies below the 20 Hz hearing threshold of the human ear) is a rapidly developing technology to understand and monitor explosive volcanic eruptions. Modest-sized explosive eruptions produce powerful infrasound signals that propagate efficiently over thousands of kilometers in the atmosphere. However, to date, these signals have been recorded by sparse infrasound sensor networks, limiting our understanding of their source generation and propagation through the atmosphere. The EarthScope Transportable Array (TA) is currently being deployed in Alaska, bringing the densest ever combined seismic and infrasonic network to one of the world?s most active volcanic regions. Exploiting this novel dataset, this project will advance the capability of acoustic early warning systems of volcanic eruptions for aviation safety and will assess the potential contribution of large sensor networks such as the TA to volcano monitoring. At the end of the project, an operational volcano-acoustic monitoring system resulting from this work will be implemented at the Alaska Volcano Observatory.This work will capitalize on the unprecedented seismo-acoustic dataset starting to become available as the TA records Alaska?s routine explosive volcanism with dense spatial wavefield sampling. Volcano seismo-acoustics is a rapidly advancing research field, where basic questions remain on the source mechanisms, source directionality, atmospheric propagation, and seismo-acoustic coupling from explosive volcanic eruptions. This project will focus on detection, discrimination, and location of the signals using novel methods; quantifying the seismo-acoustic wavefield; investigating the source mechanisms; quantifying seismo-acoustic wave coupling; and understanding infrasound propagation in the spatio-temporally varying atmosphere. Through a combination of data analysis and modeling, we will characterize and quantify diverse seismic and infrasonic signals recorded at a range of distances and directions from the explosive eruption source. We will address the following questions: (1) How do observed acoustic and seismic signals from explosive volcanic eruptions vary with distance and azimuth to the source? (2) How does acoustic propagation differ for various types of explosive eruptions? (3) What kind of volcanic source information can be determined from long-range seismo-acoustic data? (4) What are the wavefield sampling limitations in previous volcano infrasound studies? (5) What other infrasound sources are present in Alaska? Our team will work with the EarthScope National Office at the University of Alaska Fairbanks to help highlight this research and its impacts. Multi-media products illustrating seismo-acoustic wavefields from volcanic eruptions in Alaska will be distributed via the web for use in public information packets and education and outreach. Event catalogs and related data products will be publically available, with notable infrasound events uploaded to the IRIS TA Infrasound Reference Event Database (TAIRED).