EAPSI: Analysis of Fumarole Acoustics at Aso Volcano, Japan

该奖项支持对喷气孔发出的声音进行表征的研究，以促进对火山过程产生的声音的理解。喷气孔是活跃的火山环境中的喷口，会释放蒸汽和其他挥发物(即二氧化碳、二氧化硫等)。在高于100°C的温度下，从气孔中喷出的加压气体也会产生声波。由于声学和火山喷发的变化可能是更大规模火山喷发的前兆，所以烟雾弹的声学和除气可以让我们了解当前和未来的火山活动。火山喷流噪声是对喷发期间产生的压力波动的直接测量，可以提供有关喷发柱本身的信息。喷流噪声是由持续的、动量驱动的流体通过喷嘴(如喷气发动机的喷嘴)产生的，而火山喷流噪声是火山喷流在持续喷发期间产生的持续声音信号。在后者中，喷嘴是火山的喷口。实验室喷气发动机噪声的声学特性揭示了喷流噪声与喷流物理特性(速度、直径、质量流量等)之间的关系。然而，对于火山喷流和火山喷流噪音，这种关系仍然知之甚少。该研究将在京都大学麻生火山实验室的Takahiro Ohkura博士和Akihiko Yokoo博士的指导下进行。火山声学领域的目标之一是定量地将火山喷流发出的声音与喷发本身联系起来，但由于火山喷流和现场环境的复杂性，这一目标一直难以实现，因此需要更多数据。该项目旨在通过调查火山喷发活动产生的喷流噪音，促进我们对火山喷流和喷发柱的了解，然后将这一信息传播给各火山观测站和一般科学界。我们将在日本麻生火山部署两个次声麦克风阵列，其中一些与地震仪并置，以观察和表征气泡声学并确定其地震声学特征。前视红外辐射计(FLIR)相机也将被用来观察气体发射动力学，因为气体是人眼看不见的。该NSF EAPSI奖是与日本科学促进会合作资助的。

This award supports research to characterize the sound from fumaroles to advance the understanding of sound produced from volcanic processes. Fumaroles are vents in active volcanic environments that issue steam and other volatiles (i.e. carbon dioxide, sulfur dioxide, etc.) at temperatures greater than 100°C. Pressurized gas jetting out of fumaroles also produces sound waves. Fumarole acoustics and degassing can inform us about current and future volcanic activity, as changes in the acoustics and volcanic emissions can be precursors to larger volcanic eruptions. Volcanic jet noise is a direct measure of the pressure fluctuations produced during an eruption and can provide information on the eruption column itself. Jet noise is produced by sustained, momentum-driven fluid flow through a nozzle, such as that of a jet engine, while volcanic jet noise is a sustained acoustic signal produced from the volcanic jet during sustained eruptions. In the latter, the nozzle is the vent of the volcano. Acoustics of laboratory jet engine noise reveals a relationship between the jet noise and the jet?s physical characteristics (velocity, diameter, mass flux, etc.). However, this relationship is still poorly understood for volcanic jets and volcanic jet noise. The research will be conducted under the mentorship of Dr. Takahiro Ohkura and Dr. Akihiko Yokoo of the Aso Volcanological Laboratory at Kyoto University. One of the goals of the volcano acoustics community is to quantitatively relate sound from volcanic jets back to the eruption itself, but due to the complexities of volcanic jets and field environments this goal has been elusive, thus additional data are needed. This project aims to advance our understanding of volcanic jets and eruption columns by investigating the jet noise produced by fumarolic activity, and then disseminate this information to various volcano observatories and the general scientific community. We will deploy two arrays of infrasound microphones with some collocated with seismometers, at Aso Volcano, Japan to observe and characterize fumarole acoustics and determine their seismo-acoustic signature. Forward Looking Infrared Radiometer (FLIR) cameras will also be used to observe gas emission dynamics, as gases are invisible to the human eye. This NSF EAPSI award is funded in collaboration with the Japan Society for the Promotion of Science.